GTM roll cage modifications and race car build log [Archive] - Page 3

kabacj

06-30-2014, 10:18 AM

Can you comment on the extent of the oiling issues that has you researching a dry sump setup? Is there a possibility that baffling, running a bit more oil in the pan, restrictors and a lower volume pump (not sure if those are possible on LS motors, that is coming more from BB chevy thoughts), a big accumulator, or a combination of those might help solve the issues? I guess I'd try a lot of things before a dry sump setup, just because they involve a lot of parts and a few of them (like most race parts) require maintenance and rebuilding periodically. I'm sure they are necessary in many applications, just curious if the weight, extra volume of pressurized oil around the engine compartment, and fab time could be avoided.

HI Keith,

I also wanted to avoid the dry sump for many of the reasons you mention. Cost, complexity etc.

To keep the LS3 alive on the track I am running the MAST motorsports extra deep and baffled pan. This solves some of the oil starvation issues common in an LS3. MAST claim its good for road race applications. Adding an oil accumulator will also solve for some of the issues with oil slosh in the pan. This is probably a good solution for track days, but not the best solution for racing. I can see the oil pressure dip under G load with my current level of grip. I have decided against the accumulator (even though i alrady have it and all the hardware) as its only going to mask the issue for a short period of time as I step up my game.

Now that I need to complete with other cars I am both driving harder and pushing the car harder. This weekend I will go to limerock and Ill scuff a set of racing slicks and further setup and refine the car. The GTM can hang with many cars on slicks while running DOT R compound treaded tires. Adding Slicks takes you into a whole other area of G loads.

The reason I will swap over to the dry sump is three fold. One without the deep oil pan I can lower the motor and the CG of the car. Two with vacuum in the crank case oil is pulled through the motor instead of flowing via gravity keeping oil in the right places under sustained G load. Three the Vacuum in the motor will lower crank case pressure at high RPM that bored out LS3s are famous for. Sure you also get less drag on the crank from friction spinning through the oil so thats nice.

I look at the dry sump as insurance that no matter how high G load I get I will always have oil pressure. Its possible to get many of these benefits with cheaper / less complex solutions but none that I have found have the full package you get with a dry sump.

As crash says, Its much cheaper getting a dry sump then the motor work required to fix an oil starved engine.

John

KeithBoden

06-30-2014, 04:43 PM

Excellent and thorough answer guys, thanks! Pressure drops under high lateral loads. I agree, a whole separate forum could be dedicated to figuring out where the oil is when it isn't where you need it; I have friends that have run clear intake manifolds and without an oil pan on engine dynos (yes, what a mess) to see where it goes in various scenarios. They were worried about longitudinal loads, but you could always tilt your motor over 65 degrees to simulate a 2g load ;)

Cobra 61

06-30-2014, 08:10 PM

kabacj

07-01-2014, 06:56 AM

Hi John,
Been so busy. Congrats on your first competition race! I see there has been no mention of others long ago that attempted to race/track the GTM with oiling problems and eventually killing the motor. I haven't an answer for that and I don't remember what their conclusions were either. Our dry sump doesn't appear complicated or comparatively that pricey vs. engine replacements (plural). The single stage ASA system we have indeed paid for itself as we have run the motor out of oil on two completely different occasions. One when the oil cooler was ripped off in a wreck and the driver drove it back around the track and into the paddock. Two, the gear inside locked up at 6,000 RPM and drove a short time after.

Congrats!!!!!

Thanks Richard,

After doing the research, I fully agree that a single stage system that uses a dry sump pan, a single stage pump and an external tank to supply the standard oil pump is the minimum way to go on any track ready GTM. Clearly GM agree, as Crash also points out, GM dry sump any corvette that is sold as track ready. Thanks again for all the info that your team have shared regarding what works and the pros and cons of each setup you have used.

Thanks for the inspiration to make the GTM into a race car. I forgot how much fun it is to race. Car racing and motorcycle racing are very different, however both have their upsides. So far one of my favorite parts of car racing are the lovely girls that organize the grid and hand out the trophy’s. We never had this when I raced motorcycles.

http://i1073.photobucket.com/albums/w389/kabacj/208af369a8aacd61309631d4ab3350d2_zpsff5d5908.jpg (http://s1073.photobucket.com/user/kabacj/media/208af369a8aacd61309631d4ab3350d2_zpsff5d5908.jpg.h tml)

Factory five also reported on the race at Thompson in case you missed it here is the link.

https://www.factoryfive.com/whats-new/factory-five-makes-history-at-re-opened-thompson-speedway/

John

fastthings

07-01-2014, 07:57 AM

You stud.

crash

07-01-2014, 08:53 AM

crash

07-01-2014, 08:56 AM

So far one of my favorite parts of car racing are the lovely girls that organize the grid and hand out the trophy’s. We never had this when I raced motorcycles.

http://i1073.photobucket.com/albums/w389/kabacj/208af369a8aacd61309631d4ab3350d2_zpsff5d5908.jpg (http://s1073.photobucket.com/user/kabacj/media/208af369a8aacd61309631d4ab3350d2_zpsff5d5908.jpg.h tml)

John

That must be a local to YOU thing, as we certainly don't get that type of treatment out here. Trophies are bigger for you guys too. :(

kabacj

07-03-2014, 05:25 AM

I spent most of my time tuning the rear toe and shock damping on my last visit to Thompson raceway.

I did not even come close to testing and documenting the setup changes I planned to test.

This weekend I'll travel to lime rock park ct. Saturday is a double race day and I also will run the TT sessions that don't conflict with the races. That should give me plenty of test time.

On my list was testing the rear ARB. I am starting with the 19mm stock corvette bar. Mostly because my buddy gave it to me for free. I also think it's a good idea to move from soft to stiff instead of jumping in with a very stiff bar.

With some tabs added to the stock frame and some aftermarket c5 poly bushings it's possible to simply bolt up the stock bar in its stock orientation.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/F09D7366-3342-4B3B-9A2B-AD9AFF5A32A2_zpssf3o8n8p.jpg

The only problem is the tabs on the lower A arm are about an inch too far inboard. The GTM has the A arms mounted more inboard then the c5 , however the wheels are set outboard to compensate. With the low ride height I run the bar pick up point is a little close to the A arm.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/8C02D758-577E-42A6-9342-F175F81A554A_zpsaxwh0gug.jpg

To solve for this I could weld a tab on to the lower A arm which might impact the strength of a heat treated part. Or I could make a steel tab and attach it to the factory five shock mount support. Or I could just chop up the bar and place the pickup points in a more ideal orientation.

I went with option 3

Step 1 is flip the bar over and upside down. That both makes the bar match the contour of the GTM frame where it mounts and also gives the bar a more upward sweep on the outboard ends. Of course that also puts the mounting holes on the bar in an orientation that is not ideal.

No problem. I cut about 5 inches off the end of the bar where it makes a bend away from the angle I want. While I had the end off the bar I put it in the press and crushed it flat just like GM did for the end hole. I also added two more holes for adjustment.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/55B647DA-A88E-43D2-8E3E-96C2B015E290_zpson1cjgvd.jpg

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/171D4238-71F9-4575-B841-D512AB721E6A_zpsfglmbfr4.jpg

It was late so I decided to call it quits for the night. Tomorrow I'll make up a slug to join the ends of the hollow tube that forms the ARB. A few plug welds into the slug and a nice weld around the joint and the joint will be plenty strong I think.

The net of this change will stiffen the bar a bit as well as add some adjustment so I can decide if I need more or less bar then this setup offers.

John

longislandwrx

07-03-2014, 07:49 AM

kabacj

07-03-2014, 12:56 PM

John,

Congrats on your win! Car is really coming together. How's the weather supposed to be Saturday, perhaps I'll take a drive out to CT.

Just wait until you grab a podium finish at Limerock, you should have seen the race day girls at the grand am last year.

Thanks man,

I was very happy to bring hardware and a cool picture home from my first race.

You should come up to lime rock on Sat. Factory Five will be well represented. At least 3 challenge cars and one GTM will be in attendance. When are you going to bring your 818? :)

John

kabacj

07-04-2014, 02:14 PM

Since its a rainy 4th of July courtesy of the remnants of hurricane Aurthur , I got to do a little welding and fabricating instead of drinking beer and having a BBQ. Hmm its a toss up which is more fun...

I had to weld on the sections of the C5 ARB that I had cut off and make up new links to tie the ARB to the lower A arm.

First I welded up the arb.

With the slug inside it was an easy weld. I just built up the area so the bar looked smooth and without kinks.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/C3E64C18-C49F-40F9-955D-5C5C953E05DE_zpsfa28skav.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/C3E64C18-C49F-40F9-955D-5C5C953E05DE_zpsfa28skav.jpg.html)

next i needed to fab up new links to replace the corvette links which unfortunately dont work with the shock support as the studs are too short.

My first idea was to weld two nuts on to a length of tube as a quick and easy way to get a working solution. That process took a while, was heavy, and looked ugly. I decided I could make the part out of aluminum in less time.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/ED866155-0C0B-4F44-A51E-5C31CF5183CD_zpsnso51eed.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/ED866155-0C0B-4F44-A51E-5C31CF5183CD_zpsnso51eed.jpg.html)

That worked out well as the part is both stronger and lighter.

here are the links assembled.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/3DE1F673-60C2-40BC-A670-EAD697596906_zpsnlftqidu.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/3DE1F673-60C2-40BC-A670-EAD697596906_zpsnlftqidu.jpg.html)

and here you can see them installed.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/4BF55EFF-D06F-41AC-864A-B7D5D2B4CD36_zpsq73qsqj0.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/4BF55EFF-D06F-41AC-864A-B7D5D2B4CD36_zpsq73qsqj0.jpg.html)

I spaced the rod ends away from the A arm and nut so they have max mis alignment, but that was not necessary. As I cycle the suspension through its max travel the links stay well aligned to the motion of travel. Actually turned out better then I had hoped.

One of the benefits of flipping the ARB over is now it is more offset from the GTM frame.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/D62DFE2E-3417-450D-AE51-DBD16CD9518F_zpsafva2gbl.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/D62DFE2E-3417-450D-AE51-DBD16CD9518F_zpsafva2gbl.jpg.html)

We will see how this all works on the track tomorrow.

John

crash

07-07-2014, 09:13 AM

John,

I was watching Race Monitor this weekend...what happened?

kabacj

07-07-2014, 02:46 PM

John,

I was watching Race Monitor this weekend...what happened?

Funny you should ask Crash. Its a long story, but here goes.

The weather was GREAT following a very rainy Friday I was excited to head out to the track.

First session was the TT group I headed out and there was clearly something wrong as the car was misbehaving badly. I was actually experiencing the same issues I had experienced before I did the toe link re enforcements except now the car was unstable at high speed as well. It was far worse then ever. On and off throttle was scary!

Since I had measured the deflection on the links I was sure that was not the problem. I had just done an alignment at home and I knew that was also in good shape. I could not understand what problem I had. I could not even think of something that could break and cause this.

When i came on off the track, I figured I would just verify the toe settings again. WHAT! I have half an inch of toe out in the rear. How is that possible? I triple checked the alignment at home.

So I carefully adjusted the toe links to bring the toe to 1/8 in on both sides.

Next I went out in Thunder Qualifying. Holy cow this thing is still not working. I did not even do one lap before I came in. The car was barely drivable.

Again measured the rear toe. now I have way too much toe IN on the driver side!

I must be going crazy. I know I measured the toe properly.

Time to call a friend. I called the guys over and asked them to double check what I was doing bc for some reason I cant measure the same settings twice.

They watched what I was doing and double checked my work. Since I was had lost with the toe settings from my careful alignment at home I resorted to measuring off the frame to the rotors. measured both toe links to the frame. Squared the rear rotors to the frame then reset the toe.

I re set the rear tires to toe in - 1/8 on both sides and took the car around the paddock to try to duplicate the toe change. By this point I had missed Thunder qualifying. Lime rock does not have much area to go higher then 5mph. So I just did a few laps of the paddock and a drive out to the skid pad and back. On the way back I heard a thunk... like a bad one. Did I forget to tighten something... I waited for something bad to happen but nothing happened.

Got back and jacked the car up and checked the whole rear over . Then I saw it. The eccentric had moved . I mark the eccentric to the frame to verify that its not moving. They have never moved in many track days. I have kept them in because they are easy to adjust. I looked at the cams and they were polished from moving on the track. What’s worse is I have Crash's kit to eliminate the eccentrics.

So the reason I was having so much trouble was my toe was changing as I drove around the track. That’s bad for handling by the way.

So I took out the camber gauge. Set the camber and verified I was back at my mark on the eccentric and frame. Again set the toe and tightened it all down.

I had a TT session right before the first Thunder race. Normally I would skip that one, but this will be perfect to test the car. Ill just go out for a few laps to familiarize myself with the track I have only been to lime rock once and that was at the early stages of GTM development. After a few laps ill come in and Grid up last for Thunder Race. (since I had missed qualifying)

TT session went well and I roll up to the grid for the race, and I glance at the fuel gauge. Oh man I need fuel I don’t have enough for a 30 min race. I was all disorganized because I was chasing the handling issue all AM. With the wheels on and off so many times I killed the battery in my Impact gun. Back to the pit... very slowly through the crowded pit. I’m all the way by turn 2 on the far side of the pit from the pre grid. By the time I fill up the race has started. By the time I get strapped in and back to pre grid ill have missed another 5 laps. I decided to bag it. I have another TT session and another Thunder race in a few hours.

I started race 2 on the last row since I did not qualify. ( I was not on the grid sheet) THEN Race 2 was cut to 10 racing laps by an extended double yellow flag as a car went off at turn one on to the soaked grass at about 90. He plowed the tire barriers right over the guard rail.

So a lose nut and my forgetting to fill up the car with gas messed up race 1 and race two was super short. On the good side I know for sure what toe change mid corner feels like! It feels just like when you flex the toe link mount.

While I was at the track I mounted up some Hoosier Slicks. WOO HOO traction!! I did not run them in the race for fear of oil starving my motor before I install the dry sump. I am pretty sure Ill be a bit more competitive with these. The toyo r888 are a good street/track day tire, but they are not a great race tire if the track is dry and they are nothing like a full race slick or even a DOT slick. The racing hobby is always a saga, but its fun!

crash

07-07-2014, 03:08 PM

I bet I know the first thing your gonna do before the next race... :)

kabacj

07-07-2014, 04:00 PM

I bet I know the first thing your gonna do before the next race... :)

Yeah that's for sure. The st2 corvette guy pitted next to me was like oh yeah throw away those cam adjusters they are junk on the track. He missed the race because his motor blew up so I felt a little better.
Things can always be worse.
John

crash

07-07-2014, 04:26 PM

Yeah that's for sure. The st2 corvette guy pitted next to me was like oh yeah throw away those cam adjusters they are junk on the track. He missed the race because his motor blew up so I felt a little better.

John

He didn't have a dry sump?

kabacj

07-07-2014, 04:51 PM

He didn't have a dry sump?

Ha that was my first question too. He has a race built 419 LS 3 like I do, but he put the dry sump in. He also said put the sump in ASAP. He had what seemed like an mass airflow sensor issue that he replaced. Maybe the damage was already done however. The motor smelled like it had overheated. Maybe ran too lean and did the damage that way. But he lost power. Did not sound like a cheap fix.

He said he is going back to a GM crate motor :)

LCD Gauges

07-07-2014, 09:34 PM

You have some great looking linkage parts on your car! Even better than you made most of them yourself.

kabacj

07-08-2014, 05:30 AM

You have some great looking linkage parts on your car! Even better than you made most of them yourself.

Thanks man. This was one of those rare occasions where everything just worked out and I had good looking parts fast.

For those looking for wheel options I got these from 0Z racing. They are very light and strong enough for the track

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/77E4859D-F56E-42D5-A7B4-F577184AF96F_zps51p5ycmh.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/77E4859D-F56E-42D5-A7B4-F577184AF96F_zps51p5ycmh.jpg.html)

John

mikespms

07-08-2014, 07:37 AM

kabacj

07-08-2014, 03:38 PM

Hey John,

The car is looking like a race car,are you planing on registering and using it on the street? Did you install the a/c unit in the car? I had a 74 vette w/o a/c back in the 70's when I live in Long Island and it was unbearable in the summer and the after market dry sump systems uses the a/c mounting spot for the scavenge pump. Have you looked into a stock LS7 set up with a Katech upgraded scavenge pump allowing you to keep the a/c if you want it.
On the rear camber cam adjusters I had the same problem under hard acceleration and it was dangerous to say the lease.
Hey Mike, I was thinking the same thing that the car is starting to really look like a race car.

I will register it on the street. It will be street legal mostly so I can drive it a bit in the late fall/ early spring when there are not any races. I can test out basic systems and the aero bits during the season, not at speed of course, but more for normal operation, and of course just so I can enjoy it when ever I want.

Back when I set the spec for the motor, I actually held off on the dry sump because I wanted to keep the AC. Since I have started racing the car, and I have my target on going as fast as possible. I am going to swap out the AC and put in the dry sump. Its possible to keep a full blown dry sump and the AC, but I want to shed the weight of the AC as I really can’t use it most of the time. My GTM is getting so extreme it will make a fun car to drive on the street, but its not going to be my first choice to take the wife out to a fancy dinner… or maybe it will .. ha ha. But a the car is drifting away from the capable GT car target to the hard core no holds barred race car.

What’s weird is on the camber adjusters I never had a problem until this past weekend. I think it matters a lot how you have the camber set. If the bolt is at 3 o'clock or 9 o'clock the A arm does not have as much leverage to twist the adjuster as if the bolt is at 12 or 6 o’clock. Needless to say once you get your camber set its a good idea to delete them. The GTM does not like when one wheel toes out or in 3/8 inch at a time.

Presto51

07-09-2014, 11:49 AM

What’s weird is on the camber adjusters I never had a problem until this past weekend. I think it matters a lot how you have the camber set. If the bolt is at 3 o'clock or 9 o'clock the A arm does not have as much leverage to twist the adjuster as if the bolt is at 12 or 6 o’clock. Needless to say once you get your camber set its a good idea to delete them. The GTM does not like when one wheel toes out or in 3/8 inch at a time.

Hey John

Wondering over here, do you think that the modification that you did to the rear, influence\increased, the stress load placed on the camber adjusters, causing the Scotty effect of "I've giv'n her all she's got captain, an' I canna give her no more."

Or some call it ....

The mechanical domino effect, that occurs when a small change, causes a similar change nearby, which then causes another similar change, and so on, in linear sequence.

If you think that is the correct assumption, maybe study what other areas that might be affected when you change out the stock adjusters for the shims, making it possible to identify the next point of failure?

Of course it's easy to sit here and pontificate, but it looks to me that you are shooting for faster speeds and lap times, I'm just going along the lines of thought of keeping your race outings fun instead of frustrating.

Ron

crash

07-09-2014, 12:04 PM

johngeorge

07-09-2014, 01:23 PM

Thanks man. This was one of those rare occasions where everything just worked out and I had good looking parts fast.

For those looking for wheel options I got these from 0Z racing. They are very light and strong enough for the track

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/77E4859D-F56E-42D5-A7B4-F577184AF96F_zps51p5ycmh.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/77E4859D-F56E-42D5-A7B4-F577184AF96F_zps51p5ycmh.jpg.html)

John

Now we are talkin!!! Finally some real rubber on this bad *** car :) when is the next track time with Hoosiers?

kabacj

07-09-2014, 04:54 PM

Hey John

Wondering over here, do you think that the modification that you did to the rear, influence\increased, the stress load placed on the camber adjusters, causing the Scotty effect of "I've giv'n her all she's got captain, an' I canna give her no more."

Or some call it ....

The mechanical domino effect, that occurs when a small change, causes a similar change nearby, which then causes another similar change, and so on, in linear sequence.

If you think that is the correct assumption, maybe study what other areas that might be affected when you change out the stock adjusters for the shims, making it possible to identify the next point of failure?

Of course it's easy to sit here and pontificate, but it looks to me that you are shooting for faster speeds and lap times, I'm just going along the lines of thought of keeping your race outings fun instead of frustrating.

Ron

Hey Ron,

Yes I think the mod may have increased the stress load on the adjusters, however I think I simply left the adjusters looser then I would normally becuase I planned on doing an alignment after the welding was finished.

As always life got in the way and I did not have enough time to do the alignment so I never fully tightened the passenger side cam adjuster.

The adjusters were left in their semi tight state and when to thompson. After three days I started to loosen them up and I attributed the instability I had under braking to the alignment I did not do. I consequently was making changes and testing. But I was never happy with the setup. Of course I didn't realize the adjuster was moving.

Before I went to limerock I did my alignment at home and triple checked it. That made me sure that everything was fine. Coincidentally, When I did the alignment the passenger side rear camber was exactly where I wanted it. I never touched the adjuster. Therefore the adjuster was still loose when I went to Limerock.

Its bad to be sure of anything becuase I over look things when I am sure they are not the problem. :)

yes its a good point to make sure that eliminating the cam adjusters will not cause some other issue. I will double check that when I do the install. Since its a common fix on the corvettes and the PDG team and others also have done it im reasonably sure its ok. But like you say I have lots of other mods and its important to watch out for other effects.

I was thinking maybe the slicks had something to do with it?

I agree with you the slicks could be a reason for the camber adjusters to move, but I had not put the slicks on yet. I wanted to make sure I had sorted the car out with the toyo 888 package before I added another variable. Turned out I only put the slicks on for a few laps after the races at the end of the day. They are AWESOME!

John

kabacj

07-09-2014, 05:10 PM

Now we are talkin!!! Finally some real rubber on this bad *** car :) when is the next track time with Hoosiers?

Hey John. BTW GREAT job at limerock. Everybody should check out the videos of John on the track at limerock on this thread.

http://thefactoryfiveforum.com/showthread.php?15026-Factory-Five-Racers-John-G-and-Pat-M-Dominate-at-Lime-Rock

You really cant get an apreciation from the video how well John is working the car to get around so quickly. Limerock does not have run off esp this weekend bc the grass was like ice. IF you leave the track you wreck as we saw when a Panoz in our race group went wide into turn one at about 80 and took out the tire barrier as if it was 5 feet from the track even though it was quite far way.

So next track visit for me will be either July 29th again at limerock with the SCDA, or August 13 open track with NASA. Unfortunately I cant make the next race July 19th at NJMP. I am looking forward to getting back to New Jersey motorsports park where I have a baseline for what the old GTM can do. It should be much faster.

I'd love to go to road Atlanta for the championships. Not sure if I can make that happen.

After that its watkins glen in August with the porsche guys and the NASA races in Sept and Oct. With a few track days thrown in. Boy the race season goes quickly.

We have three factory fives showing up at the races now. We need a few more.

John

Plebeian

07-09-2014, 09:18 PM

How much does the AC weigh? I can't imagine having a GTM I was still going to drive on the street and not having AC.

kabacj

07-10-2014, 05:36 AM

How much does the AC weigh? I can't imagine having a GTM I was still going to drive on the street and not having AC.

The whole AC system is about 35 lbs. I'll let you know exactly as the GTM goes on a diet this month. My goal is to take everything that does not make it faster out with exception to the heat / ac core. The AC compressor and condenser are easy enough to take out and re install later if I wanted to.

I agree for a street car AC is a nice thing to have and I also thought it was a requirement, but I think the fact that I am taking it out gives you an idea how much fun this car is on the track. Right out of the box the GTM is much closer to a race car then a production street car because you are adding things to make it street friendly instead of taking them away to make it track friendly. The AC also does not work well when you must keep the windows open. (In my case I leave them home)

When a car company builds a production car it's one giant compromise. Production cars try to be all things to all people. They do an amazing job of it, but lack the focus I wanted.
When I started the GTM I wanted to build a no compromise GT car that was as well suited to the street as a recreational track day. That's possible and reasonable. I was well on my way , but now my focus has changed.

The fastest guys in super unlimited are running 900 hp track only race cars. I'm trying to get my 630 hp GTM in the same ball park. That means I need to optimize everything I can for racing. That also means I compromise street friendliness in the name of ultimate track performance.

Now I could always try to focus the GTM on a class with some rules but I like the sound of super unlimited. Don't you? :)

John

RumRunner

07-10-2014, 06:57 AM

Now I could always try to focus the GTM on a class with some rules but I like the sound of super unlimited. Don't you? :)

John

John,

I think that sums it up nicely :cool:! Super Unlimited does have a nice ring to it.

-Michael

crash

07-10-2014, 09:19 AM

Just to let you know, we would likely NOT be running Super Unlimited with the PDG GTM except for the center steer modification. This was done to increase fuel capacity and to make the car a bit safer by moving the driver to the center where the roof is higher, but if we didn't have to do that we could have qualified for a few different classes that would have been much easier to compete in. For the endurance stuff, we probably still would have been in ES class though. You should be able to compete with everything but the fastest sports racers in Super Unlimited with 630 HP. We do, and we only have a bit over 500...but if a real Grand Am car or Trans Am car shows up, it's another story. There ARE some pretty fast purpose built race cars out there. We end up running frequently with NASCAR Cup cars and although they definitely have a HP advantage and a tire advantage, we run with them and beat many of them pretty easily depending upon the track. You might want to look into the other NASA classes available as it is really nice to run close to someone else in times and that doesn't usually happen in SU.

kabacj

07-10-2014, 04:52 PM

You should be able to compete with everything but the fastest sports racers in Super Unlimited with 630 HP. We do, and we only have a bit over 500...but if a real Grand Am car or Trans Am car shows up, it's another story. There ARE some pretty fast purpose built race cars out there. We end up running frequently with NASCAR Cup cars and although they definitely have a HP advantage and a tire advantage, we run with them and beat many of them pretty easily depending upon the track. You might want to look into the other NASA classes available as it is really nice to run close to someone else in times and that doesn't usually happen in SU.

True good points. I'm going with SU for now. The only experience I have is racing my 125 GP bike. If you can carry corner speed you can overcome quite a large HP deficit. Add really good brakes and you have a package. I like impossible projects. It would be cool if I could run with any SU car out there. I'm going to try.

johngeorge

07-11-2014, 06:48 AM

John, the good part of NASA-NE there seems to always be a good number of SU cars that show up to events, its almost the only region that has that many SU cars running all the time.

crash

07-11-2014, 09:22 AM

John, the good part of NASA-NE there seems to always be a good number of SU cars that show up to events, its almost the only region that has that many SU cars running all the time.

That's great. Not like that out here. We are lucky to see five cars on a weekend and usually it is more like 2 or 3. Sucks for tire contingencies. Really this is our biggest issue with running slicks. Hoosiers will only be sticky for 3-4 hours of racing, even with having plenty of tread depth available, and at $2000 a set and us running 3 hour enduros, well, the tire costs add up quickly. Between tire, fuel, brake and driving to the track costs, it can easily cost $5000 to run the car every weekend. We have done as many as 33 races in one year. That adds up pretty quick and makes the DOT tires without a doubt the best bang for the buck. I think with the small brakes and DOTs we ended up more like $2k a weekend. There's a pretty big difference between $66,000 and $165,000 a year in costs to run a race car. Especially at the amateur level. Most people have no idea what it costs to run a racing program. We could literally all have a new GTM, or Coupe, or Roadster every year...everyone of us on the team!

flickery8

07-17-2014, 06:28 PM

Hey Dave,

Sounds like fun. What track are you planning on visiting?

As you can see from the experts the GTM is very sensitive to alignment.

here is the setup I used last year that worked well.

Left Front Right front
caster -3 caster -3
camber -2.8 camber -2.7
toe -1/16 toe -1/16

Left Rear Right Rear
camber -1 camber -1
toe -1/16 toe -1/16

for this time I am going to try toe out as Ted suggests.

I will also try a little more rear toe as Mike suggested.

I will also remove .25 degrees of camber from the rear. I found that I was getting a little too much heat and wear on the insides of the rear tires.

Also note that i did not see any ill handling until I started to really carry some G load. On my best lap last year I pulled 1.6 Gs.This past weekend I was pulling 2Gs

Im not saying that you are not having the same problem, just saying that I would first make sure the alignment is good then start chasing other things. Like I said I had a very stable car going faster then all or most all of the guys at the track last year. It was only going up against full on race cars that brought out my current issue.

You are also running a big torquey turbo motor so maybe you are showing the same toe link flex. No sure. I would go with the alignment as the first thing to concentrate on however.

You should try to get some rear suspension video if you can. Im going to rig up several camera angles before I go to the track in case I dont solve the problem.

John

I have spent the past couple days reading this whole thread. Wish I had found it a year ago. I do recall reading some of the early tube modifications, but the thread needs a new title. This is so much more now.

Anyway, I am very curious to hear your impressions of the toe out on the front.

Also, are still running 450# springs in the front and #750 in the rear http://thefactoryfiveforum.com/showthread.php?5318-Ohlins-shocks-for-my-GTM&highlight=spring ?

Thanks for the info!

kabacj

07-18-2014, 09:53 AM

I have spent the past couple days reading this whole thread. Wish I had found it a year ago. I do recall reading some of the early tube modifications, but the thread needs a new title. This is so much more now.

Anyway, I am very curious to hear your impressions of the toe out on the front.

Also, are still running 450# springs in the front and #750 in the rear http://thefactoryfiveforum.com/showthread.php?5318-Ohlins-shocks-for-my-GTM&highlight=spring ?

Thanks for the info!

Yes I am still running 450# front and 750# rear.

The only thing I need to change with the shocks is the damping rate. Performance shock setup the front and rear perfectly for the street/ track but now that I am more focused on racing I could use more damping. At least at Thompson where there are some rough transitions from the old oval to the new road course.

I should see about changing the thread name. I agree now it's more a log of my mistakes and successes setting up the GTM for the track.

Glad you found it helpful.

John

kabacj

07-28-2014, 05:35 AM

The first step to install the dry sump is to remove the A/C compressor. I was really dreading the dry sump install because I figured it was going to require pulling the motor to get everything apart. I was pleasantly surprised. It's actually not that bad to pull the compressor.

First remove the aluminum sheet that covers the tunnel and accessories under the motor. It's was good to use silicone (instead of something more adhesive) as a vibration damper between the panel and frame because the panel comes right off. Of course there are 50 rivets to drill.

Next remove the header. In order to remove the bolt the attaches the A/C lines to the compressor the headers need to be moved.

Next it's just a matter of unbolting the A/c bracket from the block. The two bottom bracket bolts take a while unless you have a high quality 15mm ratcheting box end wrench. I don't. With a normal open end wrench you need to turn bolt flip the wrench turn the bolt a few hundred times backing out the bolt a degree at a time.

There is not a lot of room in this area, but it was reasonably easy to drop the compressor and bracket out from under the car.

Next was the harmonic balancer. I did not want to remove all of the plumbing in front of the motor. Mostly to save time and avoid the cooling system refilling procedure. I just moved the cooling tubes out of the way and installed the puller. A few min later the balancer was out. Again the balancer drops out from under the car without issue.

The dry sump arrives this week. I went with the 4 stage ARE. Lots of plumbing ahead of me.

John

kabacj

07-31-2014, 05:28 AM

I got the parts to install my dry sump. Boy are they nice. The welds are exceptional. The machine work and finishing are done just like I would if I made every part myself. Everything is made as if money and time were no object. It's so rare to see parts this well made. What's even better ARE is an American, family owned small business.

Did I mention welds on the oil tank are AWESOME!

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/2C3AC570-C806-46A4-8708-9C1481913192_zps7ivf6dwl.jpg

I went with the three gallon tank because more oil is better to guarantee a good supply of de aerated oil to the motor.

Also went with the 4 stage scavenge pump. This will ensure good evacuation of oil from the pan as well as adjustable oil pressure.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/645E14C9-4FFF-4ABE-917E-77458573C9CD_zpsihxxdry0.jpg

The roots type scavenge pump will also pull a bit of vacuum in the crank case lowering crank case pressure and blow by at high RPM

Even the oil filter relocation plate is an impressive piece of manufacturing.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/6D6FB936-4BAB-4CB1-81AF-0D01B02F3D90_zpswfpnyxim.jpg

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/7D45EF00-560D-48E0-ADB8-F4D3B082305D_zpsn8aikcvf.jpg

I'll get everything mounted then I'll make up the lines to connect it all up. It sure will be nice to know that I'll always have oil pressure. Any time I was pulling lots of Gs I would worry that I was pushing the Mast wet sump setup a bit too far.

Now I am free to make as much grip as possible. Grip is like HP . You never have enough :)

John

LCD Gauges

07-31-2014, 05:37 AM

Wow, nice stuff. The welds around the circumference of the reservoir look like artwork!

You should pick up a few HP with that system.

kabacj

07-31-2014, 07:00 AM

You should pick up a few HP with that system.

That's true. The claim is +10hp on the dyno.

I see that as gravy. I have been gambling re oil supply under G load for a while now.

If I burn up the bearings I would be down 632 hp :)

Fraser D

07-31-2014, 08:43 AM

kabacj

07-31-2014, 05:42 PM

John,

I am very keen to see how your dry sump system comes together.
From what I have researched so far ARE seems to be the best fit for the GTM without taking out a 2nd mortgage on the house.
Why did you choose the 4 stage over the 3 stage?
I am very reluctant to loose the AC so I am looking into creative ways to mount the pump.
Are you still looking to mount the tank in your empty fuel tank cavity?

Hey Dave,

Yes I plan to put the oil tank in the cavity behind the drivers seat that would have held one of the corvette fuel tanks. When I relocated the tank to the passenger side my plan was to place all of the dry sump gear in that vacated space. I had gone back and forth with building an LS7 vs the LS3 and that space was always designed to accept the oil control plumbing. Its still not an easy fit Actually might have been easier if I went with one of the tall and thin corvette tanks , but the larger volume 3 gal tank allows some time for the oil to de aerate before it goes back into the motor.

Regarding the AC. I had held on to the Since most of my street driving will be done in the spring fall and winter I think I can get away with no AC.

Track driving of course the windows are always open (actually I don’t even have them installed in the door on the track) so AC really does not help.

I’m not going to get rid of any of the AC kit because some day I may want to install it.

It seems like its easier to relocate the scavenge pump then then AC. The scavenge pump is much lighter and the ATI damper can be configured with belt drive for the AC and a toothed drive for the scavenge pump on the front. That whole thing is a serious project that I don’t have time for currently. I just want to quickly get the dry sump installed and finish the racing season. Over the winter I can worry about how I would install the dry sump pump in another location to keep the option of running AC.

I went with the 4 stage as it offers the ability to control the oil pressure. That’s the main benefit of the pressure stage as part of the pump. Adjustable oil pressure allows me to optimize for the clearances in the motor and again save a little HP as I am not pumping oil at too high a pressure.

The 4 stage still has 3 scavenge stages which are important to both clear the pan of oil and also to develop vacuum. Ill get a bit more HP with the vacuum in the crank case and I went with an oil pan that has sumps that gather the oil and keep the scavenge pump primed. According to Gary Armstrong just having the three small sumps in front of each scavenge pickup in the pan is worth 10hp in itself.

John

kabacj

07-31-2014, 05:49 PM

John,

I am very keen to see how your dry sump system comes together.
From what I have researched so far ARE seems to be the best fit for the GTM without taking out a 2nd mortgage on the house.
Why did you choose the 4 stage over the 3 stage?
I am very reluctant to loose the AC so I am looking into creative ways to mount the pump.
Are you still looking to mount the tank in your empty fuel tank cavity?

Hey Dave,

Yes I plan to put the oil tank in the cavity behind the drivers seat that would have held one of the corvette fuel tanks. When I relocated the tank to the passenger side my plan was to place all of the dry sump gear in that vacated space. I had gone back and forth with building an LS7 vs the LS3 and that space was always designed to accept the oil control plumbing. Its still not an easy fit Actually might have been easier if I went with one of the tall and thin corvette tanks , but the larger volume 3 gal tank allows some time for the oil to de aerate before it goes back into the motor.

Regarding the AC. Since most of my street driving will be done in the spring fall and winter I think I can get away with no AC.

Track driving of course the windows are always open (actually I don’t even have them installed in the door on the track) so AC really does not help.

I’m not going to get rid of any of the AC kit because some day I may want to install it.

It seems like its easier to relocate the scavenge pump then then AC. The scavenge pump is much lighter and the ATI damper can be configured with belt drive for the AC and a toothed drive for the scavenge pump on the front. That whole thing is a serious project that I don’t have time for currently. I just want to quickly get the dry sump installed and finish the racing season. Over the winter I can worry about how I would install the dry sump pump in another location to keep the option of running AC.

I went with the 4 stage as it offers the ability to control the oil pressure. That’s the main benefit of the pressure stage as part of the pump. Adjustable oil pressure allows me to optimize for the clearances in the motor and again save a little HP as I am not pumping oil at too high a pressure.

The 4 stage still has 3 scavenge stages which are important to both clear the pan of oil and also to develop vacuum. Ill get a bit more HP with the vacuum in the crank case and I went with an oil pan that has sumps that gather the oil and keep the scavenge pump primed. According to Gary Armstrong just having the three small sumps in front of each scavenge pickup in the pan is worth 10hp in itself.

John

kabacj

08-03-2014, 09:44 AM

Started the dry sump install today. The goal was to quickly install the sump without removing the motor.

I spent some time planning where all the plumbing/ oil tanks/ oil filter would go. When I was satisfied I had a shot at making this happen I pulled the pan.. Well I attempted to pull the pan. Unfortunately it was impossible to get the pan out. The pan was hanging up on the oil pickup tube. I could not drop the pan low enough to clear the pickup tube since the pan was trapped between the frame cross tube and the motor.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/74809027-1472-4D22-BA6B-44BEE579823C_zpsdotawlhi.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/74809027-1472-4D22-BA6B-44BEE579823C_zpsdotawlhi.jpg.html)

After laying on my back under the car for 5 min I decided I can just jack up the motor a bit. I also don't have much clearance above the motor as I built the roll cage to wrap around the front and top of the heads and intake and fuel rails.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/983B3602-B585-4355-8747-747C1A869DB1-8005-0000179655BBEEBC.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/983B3602-B585-4355-8747-747C1A869DB1-8005-0000179655BBEEBC.jpg.html)

I put a bottle jack under the motor mount studs with the nut installed a few turns and was able to raise the motor just enough to get the pan out. Whew.

Here is a shot of the MAST motorsports pan. It does a great job of keeping the motor supplied with oil for track days but i don't know if its up to the task of maintaining oil pressure with slicks under racing conditions. Better be safe then sorry.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/0339A2C6-3260-4DB8-8268-43CE60F6C9D5_zpsii4t0cqz.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/0339A2C6-3260-4DB8-8268-43CE60F6C9D5_zpsii4t0cqz.jpg.html)

Here you can see the baffles cast into the pan that keep the oil from sloshing around.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/61EB5345-0AB4-4B34-96BB-29A1016FFE61_zpso266rqrq.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/61EB5345-0AB4-4B34-96BB-29A1016FFE61_zpso266rqrq.jpg.html)

So all was going well until I tried to install the dry sump pump.

The fourth stage of the pump (that provides pressure) hits the LS1 motor mount. It hits the thin web piece you can see in this photo.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/motormount_zps8287f4ff.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/motormount_zps8287f4ff.jpg.html)

I still have some fabrication to do in order to mount the tanks and oil filter but while I do that I need to decide if I do some surgery followed by reinforcement on the motor mount or if I just send the 4 stage back and get a 3 stage setup that will bolt up. I knew the 4 stage would be close... I just hoped it was going to work out.

I'm open to ideas if anyone has them.

John

kabacj

08-06-2014, 05:43 PM

I was ready to give up on the 4 stage ARE dry sump setup, but the benefit of controlling the oil pressure and the delay / potential issues with swapping the stage 4 with the stage 3 have convinced me to just suck it up and fix the ls1 motor mount I have. The stage 4 does work with some ls3 corvette mounts, but as far as I can tell all GTM builders end up using ls1 mounts on what ever motor they install. It's necessary to grind a tiny bit of the ls1 mount to bolt it to an ls3 block abut that takes all of 5 min.

Before I re invent something that somebody has already built I wanted to check if anyone knows of a company producing after market ls1 motor mounting brackets.

The key feature would be the elimination of the thin webbing shown in this picture but still installing using the stock LS1 bracket pickup points.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/motormount_zps8287f4ff.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/motormount_zps8287f4ff.jpg.html)

Thanks
John

Fraser D

08-07-2014, 12:45 PM

John,

Can you space out the pump mount to gain enough room?
Does your pump mounting bracket bolt straight to the block or to the AC adaptor plate?

kabacj

08-07-2014, 08:44 PM

John,

Can you space out the pump mount to gain enough room?
Does your pump mounting bracket bolt straight to the block or to the AC adaptor plate?

Hey Dave.

The 4 stage mounts directly to the block.

The two posts on the pump mount to the same holes used by the AC compressor with the supplied small bracket. The pump needs to fit into the L shape of the bracket. If its lower or farther away from the block it hits the lower pad of the motor mount.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/463423C8-BB03-4F2B-A137-1E2F238BF380_zpsqoslkstx.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/463423C8-BB03-4F2B-A137-1E2F238BF380_zpsqoslkstx.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/F9A29513-AA81-44E5-B447-11A6D89F8BCA_zpsb1cjnlfe.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/F9A29513-AA81-44E5-B447-11A6D89F8BCA_zpsb1cjnlfe.jpg.html)

I have scoured the internet for pre made motor mounts that will fit but it looks like fabricated steel mounts are what most people use .

Interestingly you had asked about the advantages of the pressure stage. I checked my telemetry and my oil pressure drops 15 psi from cold to hot.

I start at 60 cold so that's not too bad. I have an oil pump that was modified by Mast Motorsports to deal with track conditions.
If you start lower you might have issues. It definitely gives you less lee way regarding oil pressure under high G conditions if you keep the GM design or even if you use a modified pump.

So I was obsessing about how I was going to over come this problem and I decided that I should just cut the stock mount and see how it fits. It hurts me to cut such a nice part.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/ED77A98C-66C1-4388-A997-983D5FB2DA7D_zpsdy1appkh.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/ED77A98C-66C1-4388-A997-983D5FB2DA7D_zpsdy1appkh.jpg.html)

but GREAT news. The 4 stage will fit just fine. The tail section of the pump fits right inside the L shape of the mount. I will clean up the rough cuts and figure out where I will add the structure back into the mount where it will not collide with the pump. What a relief. I did not want to spend a day or two fabricating parts. This fix should only take an hour or so.

John

kabacj

08-14-2014, 04:14 PM

I decided to go with the four stage and that means I needed to modify the passenger side motor mount. The ARE 4 stage is designed to fit without modification to an ls3 running ls3 motor mounts. Well I have half of that setup so I just need to make the LS1 part of the setup work.

While I was modifying my ls1 mounts that already line up with the fame I realized I probably could use a stock ls3 mount and simply move the mounting point on the frame.
Too late for that now. I have an ls1 mount and I am going to make it work because that is the fastest solution.

There are two things blocking the 4 stage dry sump pump.

First the web support in the stock ls1 mount

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/motormount_zps8287f4ff.jpg

The ls3 mount is slightly more rearward then the ls1 so the forward edge of the mount hits the pump. Because I am a wood worker and used to working with an irreplaceable raw material. (The perfect grain board) I am used to slowly cutting away until something fits exactly. One over zealous cut into the perfect board and it's firewood.

I used the same approach with the mount. First removing a bit. I cut off the section right of the line.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/0A182457-8BB0-4F09-85EE-C563209D1030_zps1nqlebis.jpg

Then a bit more I cut up to the edge of the pfadt mount where the line is marked.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/6E3FE34E-3466-4B88-B63F-B55752580E7F_zpszrbru2y4.jpg

Now the mount and pump fit perfectly tucked right up close to the motor in the spot the A/C compressor once occupied

Next step was to add structure back into the mount. It actually looked strong enough as it was, but some engineer who has far better tools then I to estimate the strength required built in the support I cut out.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/ED77A98C-66C1-4388-A997-983D5FB2DA7D_zpsdy1appkh.jpg

So I welded in some more structure.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/AAB20026-0A1E-4631-84E0-81E2ED232C65_zpsa4fjnv0h.jpg

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/7DD2D876-507D-48DE-B102-060185463141_zpsqviztedp.jpg

And here is it all ready to mount back in the car.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/31CC9D91-DB5A-446A-B1AB-D25095302901_zpsyd1cqu0m.jpg
My gut says it's plenty strong now.

On to the next challenge. Plumbing the system and mounting the oil filter and vent tank. I have a ton of AN fittings and hoses on their way. Hopefully they arrive before the weekend.

John

kabacj

08-16-2014, 01:07 PM

Since I am going with the 4 stage dry sump, three scavenge and 1 pressure, that means I need to remove the oil pump. Since I have the whole front of the motor apart anyway this step was pretty easy even though the motor is still in the car.

The only issue is that the hole in the block that is normally the high pressure side of the pump is open. With my configuration I actually dont think I need to block this hole but maybe some day i will want to change the oil flow and blocking this port would be required. So just for a bit of insurance I decided to block the hole. Of course there is a cheap part you can buy that will block this hole, or you can simply tap the hole and install a plug. Tapping the hole would make a mess, so I decided to go with a bolt in plug.

Since I would need to wait for anything I would buy to be delivered and that would halt my progress on this part of the setup so I decided to make the plug. Here is what I came up with. First i cut and drilled a scrap of 1/4 inch plate then turned a bit of rod to act as the plug.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/05954D0D-590A-44E2-9C16-DA85530EA9A1_zpst8gjhvpt.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/05954D0D-590A-44E2-9C16-DA85530EA9A1_zpst8gjhvpt.jpg.html)

I turned a groove to hold an O ring that fits snugly in the hole in the block.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/CA027030-16E4-41DC-94AB-4224169A8A15_zpsrlngtzuf.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/CA027030-16E4-41DC-94AB-4224169A8A15_zpsrlngtzuf.jpg.html)

I welded the plug in and installed the o ring. Now its ready to install.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/D5A7E5E9-A70F-477F-B618-DA3DC24F5805_zps1gr0mbcg.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/D5A7E5E9-A70F-477F-B618-DA3DC24F5805_zps1gr0mbcg.jpg.html)

and here it is installed in the block.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/922028F9-C7B2-4D0B-BFE0-4E00FCFD8332_zpsruism2pz.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/922028F9-C7B2-4D0B-BFE0-4E00FCFD8332_zpsruism2pz.jpg.html)

That did'nt take very long and now I am sure I wont have any issues with oil flowing backwards out of what was the input hole for the oil pump.

John

LCD Gauges

08-16-2014, 02:10 PM

Those welds are like tiny bits of heaven raining down on the aluminum...

Nice job on the oil plug; that's a low pressure area so you should have no issue with leaking using your method.

kabacj

08-16-2014, 02:41 PM

Those welds are like tiny bits of heaven raining down on the aluminum...

HA ha. Thanks.

kabacj

08-20-2014, 08:17 PM

The next step of the dry sump install is the plumbing. I plan on using the 14mm input in the block as my oil pressure feed. In this case I remove the oil pump from the front of the motor and the oil circuit from the oil pump through the filter gets blocked off.

http://i1073.photobucket.com/albums/w389/kabacj/drysump_zpsd704057b.png (http://s1073.photobucket.com/user/kabacj/media/drysump_zpsd704057b.png.html)

The new input is where the arrow is.

I needed to port the block and the oil pan a little to make clearance for the fitting.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B9F5B75E-0634-43D1-AE5B-FE1ECB03DE57_zpsuoqlr6ey.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/B9F5B75E-0634-43D1-AE5B-FE1ECB03DE57_zpsuoqlr6ey.jpg.html)

The path the oil will take looks like this.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/are-plumbing-schematic_zps8b0b8d49.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/are-plumbing-schematic_zps8b0b8d49.jpg.html)

So I counted out the fittings and placed my order. HOLY COW! When each fitting costs an average of 20 bucks and you need quite a few feet of -10 and -12 hose the parts bill adds up quickly!

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/98AA9BB8-3DAA-4967-883A-C921917A5C72_zpskgfknp3c.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/98AA9BB8-3DAA-4967-883A-C921917A5C72_zpskgfknp3c.jpg.html)

IF im lucky ill get everything installed this weekend and ill be able to fire her back up. Im sure I will be missing at least one fitting.

John

crash

08-21-2014, 09:33 AM

kabacj

08-21-2014, 04:48 PM

I don't know which pan you have, but, again, using that oil feed location on my engines made for the oil line fitting being the lowest point on the engine. If this is the case, it is not something I would recommend. Try placing a 90 fitting on there and seeing how low it gets. Mine was unacceptable to me, so I modified the pan to accept a straight AN fitting. Yeah the oil pressure port is still low, but it is a strongly welded in block of aluminum as opposed to a thin walled AN fitting that is now low on the engine. That fitting looks shorter than the one I had from Katech so maybe this won't be an issue for you, or maybe your pan is deeper. I am running the ultra shallow ARE pans.

I went with the port in the side of the block as the way to get the highest connection for oil input. I am using the ARE fitting. Its short ill measure it for you. The short fitting actually required me to clear out some aluminum from the pan and block in order to allow the fitting to thread properly as the shoulders of the hex nut on the fitting hit the block. I would imagine that’s why most fittings are longer. It would avoid this problem.

I will run a straight AN fitting out off the block fitting and even that will be higher than the top of the frame rails. If I needed more clearance I could just put a 45 degree AN fitting and I would not drop the full -10 hose diameter below the oil pan seal.

I went with the 1004M pan instead of the low profile pan as in my case at maximum I would only gain about an inch lower motor height compared to the low profile pan. But to get that much lower I would need to shave the bottom of the bell housing off as the 1004M pan is only ½ inch below the bell housing on the sequential mendiola. If you use the GM flywheel the bell housing is even larger. I would need to extend the exhaust and lower the transaxle. A bit too much work for me to do at this point.

The other nice thing about the 1004M pan is according to ARE you pickup 8-10 hp due to better oil scavenging over the shallow pan. Since I dont need the clearance I went with it.

On your low profile pan are you feeding into the pan then piping the oil up to the crank driven pump?

crash

08-22-2014, 09:01 AM

On your low profile pan are you feeding into the pan then piping the oil up to the crank driven pump?

No. All oiling pressure and scavenge functions go through the Auto Verde dry sump pumps.

Adding a good set of windage scrappers and a very strong scavenge pump should deal with the low profile pan issues. Yes the transaxle is the limiting factor on how low I can go with the engine/transaxle.

kabacj

08-30-2014, 09:34 AM

I am getting close to wrapping up the dry sump install. I just needed to address a few little items. One was mounting of the oil vapor catch can. This part attaches to the dry sump tank and allows the oil vapor to condense and then is held to be drained periodically. Keep in mind that the dry sump pump is both pumping air and oil so this is a key part of a working system.

ARE makes the catch can so it can be mounted in a typical engine compartment. Unfortunately the GTM does not have a typical engine compartment and I am just very particular where stuff goes. I found a nice spot to tuck the catch can but the mount was in the wrong spot.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/BD7D9784-43F7-4ED6-944C-71253C7374C9_zpsawaj6dhw.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/BD7D9784-43F7-4ED6-944C-71253C7374C9_zpsawaj6dhw.jpg.html)

No worries. I can fix that. I carefully cut off the mounting bracket.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/EA1F9219-FBBF-4349-A316-E3D7192A0AA9_zpspi7smgmx.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/EA1F9219-FBBF-4349-A316-E3D7192A0AA9_zpspi7smgmx.jpg.html)

I ground down the welds left behind then welded the bracket back on where its more ideal for my mounting position.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/AE8EF3ED-8C79-49BB-AF9E-D55B404D1E7F_zpsmexbzroe.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/AE8EF3ED-8C79-49BB-AF9E-D55B404D1E7F_zpsmexbzroe.jpg.html)

I was pretty happy that I could polish out the original mounting spot so that its very hard to tell where it was originally attached.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/DF432429-EAC3-494A-B428-EE144A630D99_zpsuq3xs8cn.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/DF432429-EAC3-494A-B428-EE144A630D99_zpsuq3xs8cn.jpg.html)

I am sure ARE would have sent me a catch can with the mount in the position I needed, but this was faster and more fun. After the final AN fitting arrives tomorrow I will be able to fire the motor back up and check for leaks.

John

RumRunner

08-30-2014, 11:36 AM

John,

Once again you're a shining example of ingenuity and skill and drive wrapped into one person. Really nice work. What welder do you use?

-Michael

kabacj

08-30-2014, 11:48 AM

John,

Really nice work. What welder do you use?

-Michael

Michael you are too kind. I am just having fun while I wait for the AN fitting I knew I would forget. I have all these fittings I did not use but I'm missing the one I need. Oh well.

I use a Lincoln precision tig 225.

Presto51

09-01-2014, 09:25 AM

kabacj

09-01-2014, 12:29 PM

Hey John,

Not sure if you have seen this company, Koul Tools http://www.koultools.com/products.html

Since your dancing with the AN lines and fittings I thought this might make your build life a little easier :cool:

Ron

Wow I wish I knew about that press before I started. The stainless braided lines are a bear! I ended up making wooden hose and hose end holders. They work but not as nicely as that press!

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/AE504A0F-CC09-4AF6-A1DF-17227F8E595E_zpsz89fm424.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/AE504A0F-CC09-4AF6-A1DF-17227F8E595E_zpsz89fm424.jpg.html)

I have one more fitting to do. The tolerances are very tight so each hose must be just the correct length so the fittings all end up at the proper angle on the dry sump pump. It would be great to have this all plumbed with the motor out of the car, but since the frame is so close to the pump, I don't think I would have been able to get everything to clear if the motor was out.

I'm going to get one of those presses for the next project. Thanks for the link Ron.

John

kabacj

09-12-2014, 05:24 AM

As usual the final few days prior to a track day are a thrash.

It's 6.30am Sunday. My plan was to leave for New Jersey Motorsports park 3.30am Monday. It's a three hour drive without traffic driving around manhattan. There is almost never traffic that early. We roll into the track between 6.30 and 7am. Plenty of time to setup.

Well I'll have plenty of time to setup at the track if I have a working car. The car had not yet run with the dry sump and I still had to clear the cooling system of air.

Sunday was not a good GTM work day. I had family stuff to do from 7.30am till around 1.I woke up early and made a temporary mount for the catch can and made my last hose with AN fittings and it was time to leave for the family stuff.

1.00 and I am back in the garage. I double checked the tightness of all the fittings mounted the belt and pulley on the dry sump pump and filled the system with oil. Next I need to prime the pump and build oil pressure before I start the motor. I pulled the spark plugs put 3 quarts in the motor and 6 quarts in the dry sump tank. I loosened the fittings on the pump allowing air to escape and supply oil to pump. I turned over the motor. After a few cranks. Nothing. I disconnected the supply line to the motor in order to see if anything was flowing. a few more cranks. Nothing was flowing out. Crap.

I had stuck the remote oil filter up into the cavity between wheel well area and the motor. And from that position I could not see the clearly marked in and out.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/7D45EF00-560D-48E0-ADB8-F4D3B082305D_zpsn8aikcvf.jpg

Whoops! Had the lines backwards.

I swapped them around. That's better. Instant flow on the first crank. Whew.

I started her up and wow I had oil pressure. 100psi. The directions are to adjust the pressure under track conditions at track temps.

Ok fine. I'm pretty sure that's too much pressure but probably better to blow oil out the main seal then to starve the motor.

Next was clearing out the air from the cooling system. I really wanted to have a setup where I could drain the system of air after a fresh fill up in one shot no waiting.

I have two air bleeds. One on the radiator and one installed on the water pump. I drilled and tapped the water pump housing and added a bleed screw like that found on the brake calipers.

This worked well. I simply filled system and expansion tank. After allowing the air to escape from both locations. I heated the car up to temp and allowed the water to escape from the radiator bleed fitting until the water got hot. All done in a few min without revving the motor. The kooks system is loud without cats installed. I did not want to annoy the neighbors revving the motor Sunday evening to try to force the air out as the water pump gains speed.

After attending to lots of little items it was midnight before I went to bed ... as usual. Three hours of sleep is plenty.

John

johngeorge

09-12-2014, 12:18 PM

Good luck John!

kabacj

09-12-2014, 05:05 PM

Good luck John!

Thanks John. It was a lucky day.

I wake up to lots of phone vibrating in the alarm clock charger. I see the text messages rolling in. Ha ha it's my buddy out front harassing me that I'm late. My alarm did not go off. I had made the old am/pm mistake. Everything was ready to go so I grabbed my stuff and we were on the road 10 min later.

Fast forward to my first run. We were the second group out after the organizers did some sighting laps. Seems they found some debris on the track because the cleanup crew went out after they came in. That left us idling on pre grid. I'm watching the gauges like a hawk hoping that the oil pressure would be ok and the car would not over heat.

10 min later, Finally we went out for our session. Everything was good with temps and oil pressure. I ran about 5 laps then started to wick things up. All still good. Another few laps. still good. Great now let's do some fast laps. Hmm is that oil burning i smell?

After 3 more laps I see the black flag. I go right in. The last thing I want is to dump 3 gal of oil on the track.

Turns out at high rpm I was blowing oil out the main seal. That was spraying oil on the headers and making a nice plume of smoke.

Not a surprise with the high oil pressure.

The motor was too hot to work on between sessions.

I went out in the next session and smoked less as I started shifting at 5k rpm

During lunch I had the chance to let the car cool down enough to work on it . I was able to get to the pressure adjustment screw by disconnecting the pump from the block, but leaving all the hoses attached.

I ended up skipping the next session because rushing a job with little sleep the night before is a recipe for disaster.

Here I am under the car. I just wanted to grab a pillow and get some sleep.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/EF62868F-F20F-480F-89F9-54CA3EEF6E12_zps5we649ug.jpg

Final session arrives and I am ready. I mount up my barely scuffed Hoosier slicks to heat cycle them just in case the forecast for rain tomorrow is correct.

My first few laps are cautious as I wanted to make sure the dry sump pump was ok as well as slowly heat up he tires.

I slowly increase the speeds until I am running as fast as I ever have on this track. It was awesome. I need to move my shift points a bit to optimize the new transaxle final drive ratios. But I'm ready to move on to the next phase of development. I'm very happy with the car. I dropped into he 1.29 second area for lap times. I have to setup the car to make the best use of all the new grip, but the driveline and suspension are done.

John

flickery8

09-12-2014, 05:51 PM

Fraser D

09-12-2014, 06:26 PM

Great news John.
Glad to hear that the dry sump upgrade went well with only a couple of inconveniences.

kabacj

09-13-2014, 02:45 PM

that all sounds so familiar. rushing to get ready, hope it works on the track, things go pretty well. You just left out the part where between sessions you are frantically checking/fixing things and 10 people stop by to ask you "what kind of car is that?" or tell you they have a buddy that has a kit cobra. Keep up the great work and telling us about your story.

One question, how many times have you changed brake pads, front and rear? I am starting to wonder if I even need front brakes!?! Does your car drop down on the front springs when you hit the brakes? I adjusted my bias bar last time at the track but still burning up the back much faster.

Yep. You are so right about the questions from folks. 99% of the time I enjoy it, even when im working on stuff. Just this past visit I was under the car and people stop by and have a conversation with me while I am working. It sure is a great car to meet people. The folks you meet are all very interested in what you have done and how it works. Its just another great part of going to the track.

Regarding the brakes. I did need to beef up my front springs to prevent bottoming the front suspension under braking. This would be a track only mod as you are rarely slowing down from 150 to 60 or so on the street. I think I ended up with 350 lb springs in the front.

My bias is adjusted so my fronts just lock up prior to the rear. You get a good amount of braking from the rear wheels on the GTM but I have found that its best to have slightly front bias.

Regarding the pads. I got a custom sized stoptec brake system with 6 piston fronts and 4 piston rears. 14 inch rotors on both front and rear. I get both great brake feel and also incredible brake life. I still have not changed the pads with way over 20 track days. By contrast my buddy running his C5 corvette has gone through 4 sets of pads and at least 3 rotors. I think you want to move the brake bias frontward you should not be wearing out the back pads before the fronts I don't think.

Great news John.
Glad to hear that the dry sump upgrade went well with only a couple of inconveniences.

Yep thanks Dave. It was not too bad considering I have never done it before and really did not know anything about how to get it done prior to starting. Now I know that I should have dialed down the pressure a bit before I went to the track so cold pressures are about 25 lbs higher then my ideal hot pressure.

I am looking forward to starting the body aero mods.

John

Kempo

09-14-2014, 02:23 PM

You sure are having fun with your car John. Glad to see all the development and upgrades are paying off in lap times. Keep up the good work and the updates coming.

kabacj

09-15-2014, 05:54 PM

You sure are having fun with your car John. Glad to see all the development and upgrades are paying off in lap times. Keep up the good work and the updates coming.

Thanks Hugo.

I still have a long way to go to match the lap record times in the super unlimited class, but at the same time I am solidly in the hunt on any race day.

The good news is I have a reliable car under me now. All I need to do now is learn how to drive it.

Hope to see you at SEMA

John

kabacj

09-23-2014, 07:37 PM

My next track event is two weeks away. Three fun days with the Porsche Delaware club. It's a great event where they allow open passing and I can drive with my buddies who don't race.
Although I have a punch list of items I want to look over/ maintain or improve. I was inspired by an article in racecar engineering regarding generating down force using the flat bottom of the car.

I was thinking about how I will design the diffuser.

The first item was getting it to fit at all. The mendiola sequential trans axle is a bit longer then the standard porsche G50 or even the Mendiola S5. A little surgery was necessary to get the diffuser to fit even considering the fact that I wanted the lowest diffuser angle I could get with the factory five parts.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/28E28F6D-D70D-4753-9765-3554B8BEFC9E_zpsz1ypbeox.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/28E28F6D-D70D-4753-9765-3554B8BEFC9E_zpsz1ypbeox.jpg.html)

I needed to cut a hole to clearance the tail section of the transaxle.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B892C266-0E54-41DE-929A-B50921093E05_zpsebqkkirb.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/B892C266-0E54-41DE-929A-B50921093E05_zpsebqkkirb.jpg.html)

Then the next item was how many strakes should I add and how do they impact air flow. Well lucky for me racecar Engineering had the perfect article this month. Seems 4 is the ideal number of strakes as 6 no longer gives much benefit.

check out this cool graphic.

http://i1073.photobucket.com/albums/w389/kabacj/ebc86f0b64753eb4557771b26ec21f19_zps3461de0c.jpg (http://s1073.photobucket.com/user/kabacj/media/ebc86f0b64753eb4557771b26ec21f19_zps3461de0c.jpg.h tml)

of course I need to seal up the hole I cut to clearance the transaxle and make the strakes, and that might not happen in time for me to test it out on the weekend of october 4th, but I thought it was pretty interesting data.

John

Cobra 61

09-23-2014, 10:19 PM

kabacj

09-24-2014, 05:17 AM

We had to ease a clearance hole in the defuser also. As I looked at your photo, it makes me want to redesign the whole thing into a flat chase and extend about 6 to 8 inches past the body. But it is not the rear down force these cars need, it is front and BALANCE. This has been our area noted for 8 years. WE are very close but not where the data shows we should be, even with the "platypus" canards up front. Our enemy has been the anti squat in the rear all along. As a mental note: we are now in position at setting up with a different shock set and 950 springs in the rear and a heavier sway bar. (this is what the drivers requested). We will see on Oct 4 endurance race.

R

Yep very true Richard its not hard to add more rear downforce then the GTM needs. I was thinking that using the diffuser to gain the rear downforce instead of a big wing would be a lower drag solution. Using the diffuser and a thinner chord wing hung out past the rear deck lid could net the same downforce with lower drag. I'm going to play around with it, but it might be more useful for you guys. Over 25 hours a slight reduction in drag would equate to real gas mileage.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/041c456312eeca81e62a73a94a405fd3_zps945f047b.jpg

I still have lots of basic aero changes to make with a focus on the front end downforce, but the diffuser was one thing I could work on but not need to start cutting fiberglass.

Good luck with the endurance race. I can see how heavier rear springs and bar would help. I am also going to play with the spring preload and sway bar adjustment next weekend to adjust front / rear balance to see how that works.

John

flickery8

09-24-2014, 10:11 PM

kabacj

09-25-2014, 05:23 AM

If you were running the rear open previously, pay careful attention to heat issues once you start to close it up. I have seen changes affect my coolant temps by 20 degrees. And, I'm on my third oil pressure sender this summer.

Good point thank you. I was wondering how much closing up the engine compartment would change the motor and transaxle temps.

Right now everything is open without panels directly under the motor, diffuser or hatch glass.

I plan to copy queues from this Audi R8.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/fb41c72e8933d2202be5b03e794ce4b4_zps935e46f5.jpg

Note the louvers on the hatch "glass". Note the 4 strake diffuser with swan neck wing mount. Wing hung out over the rear edge of the car. Also note the additions to the side scoops to pump air into the rear.

I figure Audi has nearly unlimited resources these days to figure out the best cooling/drag/downforce balanced solutions.

the R8 has a similar aero signature to the GTM. Copying somebody that has the resources to test tons of solutions will at least get me in the ball park.

John

fastthings

09-25-2014, 10:49 AM

Very cool stuff, this will be fun.

JCHRacer

09-29-2014, 03:35 PM

Good point thank you. I was wondering how much closing up the engine compartment would change the motor and transaxle temps.

Right now everything is open without panels directly under the motor, diffuser or hatch glass.

I plan to copy queues from this Audi R8.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/fb41c72e8933d2202be5b03e794ce4b4_zps935e46f5.jpg

Note the louvers on the hatch "glass". Note the 4 strake diffuser with swan neck wing mount. Wing hung out over the rear edge of the car. Also note the additions to the side scoops to pump air into the rear.

I figure Audi has nearly unlimited resources these days to figure out the best cooling/drag/downforce balanced solutions.

the R8 has a similar aero signature to the GTM. Copying somebody that has the resources to test tons of solutions will at least get me in the ball park.

John

Great work as usual John. I think you are on the right path looking at the Audis. When designing the diffuser, it should be designed with the rear of the car and the wing as a system. The relative location of the wing to the diffuser (both height and longitudinal position) can greatly effect the performance of the diffuser. A well placed rear wing can make the diffuser way more effective.....that usually means a lower wing mounted further back......and that means a smaller, lower drag wing can be used. My somewhat educated guess is that the FFR diffuser angle is way too steep. If the rules are open, I would glass the hole back in, decrease the angle, lengthen the diffuser and add strakes and side plates. Do up some adjustable wing mounts (with your creativity, I know you can come up with something really slick) and go do some testing to find an optimum location of a smaller wing.

Also, the more effective the diffuser, the lower the pressure is under the entire length of the car so it effect on the balance is less that adding the same amount of downforce with rear wing.

kabacj

09-29-2014, 10:00 PM

My somewhat educated guess is that the FFR diffuser angle is way too steep. If the rules are open, I would glass the hole back in, decrease the angle, lengthen the diffuser and add strakes and side plates. Do up some adjustable wing mounts (with your creativity, I know you can come up with something really slick) and go do some testing to find an optimum location of a smaller wing.

Also, the more effective the diffuser, the lower the pressure is under the entire length of the car so it effect on the balance is less that adding the same amount of downforce with rear wing.

Thanks Joel for the input as always.

I agree the stock diffuser angle and height take into account clearance for road use, and were not primarily concerned with down force. The other thing I am looking into is the fact that the rake on the whole car with side skirts lowered slightly can make the entire flat bottom of the car into a diffuser of sorts. Ideally Ill be able to get down force closer to the CG of the car and maximize down force without creating a front rear imbalance.

Ill be at the track for three days this weekend and I am going to play with springs and roll bar rates to tune low speed grip. My current setup has gone from one where I was pushing the front to one where the rear is loose but with tons more total grip. I think some of the grip imbalance is setup related. But the car sure likes the hoosier slicks with 285 soft 80 compound on the front and 355 100 compound on the rear.

I cant wait to start testing the aero stuff. Hopefully ill be able to do some slow speed simulations using yarn tufts and possibly even smoke while driving on the street to figure out the airflow path. Ill have a few setups for the track and use the stopwatch / seat of the pants to evaluate if they work.

John

johngeorge

09-30-2014, 07:40 AM

kabacj

09-30-2014, 06:10 PM

John, get yourself a GPS based datalogger! stop with this stop watch nonsense. Some loggers have shock travel, load sensors, ride height sensors, etc.. to better quantify the changes you start making.

Hey John

Very true. I have a gps data logger from stack called a clubman. It's good because it takes the CAN signal from my Bosch based ECU. The ecu will take CAN inputs like wheel speed steering rate and overlay 3 axis accelerometers with gps data.

It also allows for a secondary CAN input channel for the things that the ECU can't deal with.

And all of that is auto synchronized with up to 3 video feeds I use 2 now.

I get a reasonably good idea of what the car is doing at any point in time, however I'm a complete novice when it comes to data collection. That's another thing I will sort out over the off season.

It will be much easier to spend a day sorting all the systems on the street at legal speed. Instead of burning expensive and limited track time figuring out how to get the sensors all working.

I wish there was a killer data logger solution that was as easy and powerful as an iphone. But sadly we are back in the days of DOS and setting IRQs and interrupt values manually when you buy a data logger.

It's another project for the winter. I looked at AIM. Decided Stack was better for my purposes. Do you know of a data logger that's powerful but user friendly?

KeithBoden

09-30-2014, 10:49 PM

I wanted to add a few points relating to the diffuser, underbody, and what I believe is pretty important: the front inlet to the underbody. Stick with me, this got long, but I wanted to share :)

I'll start from the back since I don't have as much experience here, but do have some experimental data and a number of good references. Maximum diffuser angles seem dependent on how fast the air is flowing into them, how much leakage into the area is occurring, and how effectively the rear wing is helping to pump the air. (Race Car Aerodynamics: Designing for Speed, Joseph Katz) and the later cited book provide a maximum angle at around 7-9 degrees where there is a lot of leakage, or not much side sealing from vortexes, to 14 degrees for tunnels with good sealing. In the sedan-world, where there is a lot of leakage from the diffuser region to the sides, drag is at a minimum around 4 degrees, and grows by a fraction of a percent per degree up from there. Just from the looks of the Audi picture, I'd say a great deal of engineering went into the sealing of the tunnels, so borrowing elements may allow for steeper diffuser angles than with minimal strake/side plate designs. It sounds like Joel would agree, and probably has far more experience in that area than I.

Interestingly, from a number of references, the presence of the wing, angle of the diffuser, and even the length of the angled and flat sections of the underbody don't have much of an influence on the 'maximum' low pressure, either in magnitude or location. A poorly functioning diffuser or rear wing may balance the underbody-produced downforce more towards the front, but only because the rear underbody combination is performing poorly. One interesting thing to consider is that our speeds, even up to 200 mph, are relatively low mach numbers. (< .27) At these speeds, air can be considered incompressible, in the sense that that it doesn't 'back up' and become pressurized, or 'thin out' and become low pressure as a result of the shapes of the underbody. This seems to contradict some books on the matter (Competition Car Downforce, Simon McBeath, p93) "This is common sense really...if...the front was higher than the rear, then air would pack under the car at speed and give it a very unhealthy, and very unsafe, upwards lift" but this particular reference was really providing a simplification to which they correct later in stating that the rake is really to allow "the air to continue flowing rapidly - though gradually decelerating - towards the rear" and to "allow some interaction between the wake and the underbody flow, which will help to ensure that the pressure remains relatively low below the back of the car." What I believe to be important from this is: it is the relative speed of the air that is important in determining the pressure exerted on the surfaces. Returning to my comment about a poorly performing rear underbody, this equates to slow moving (or turbulent air, then causing slow moving air) in that region exerting a pressure on the underbody that is not as low as a fast moving stream would exert. It may sound like a fancy way of saying 'the air under the car is high or low pressure and then exerts force on the surface' - the distinction is that the air itself is not at a higher or lower pressure, but the effect from the speed is exertion of a higher or lower pressure on the surface. From what I have found, the underbody can be designed to minimize the slowing and turbulence of the air stream under the car, and the diffuser and wing can be designed to help return that air stream to to the wake.

So by constructing an underbody that minimizes disturbing and slowing (relative to the car) the air that is moving under the car is beneficial: the faster stream exerts a lower pressure on the surface. The next big step I believe is realizing that you can do better than minimizing the 'dragging air along' effect that is going under the car. For that, I think it is important to visualize the air under the car as a stream, or at least moving relative to the ground. Suppose you have a splitter around the entire perimeter of the car, a perfectly smooth and level underbody, with the car traveling at 100 mph. The underbody will drag a boundary layer of air along, thinner at the front, and thicker towards the rear of the car, and the stream of air under the car will have an average speed in the same direction as the car, faster near the car and slower near the ground (all relative to the ground.) You could reason that the maximum speed differential that could be attained is less than 100 mph. It is if the air stream under the car moves in the direction of the car, but we can move that stream in a direction opposite the car (relative to BOTH the car and the ground.) This would produce lower pressures than the perfect underbody case above. We can take advantage of the incompressibility of the air, and pay a drag penalty to accelerate the air to speeds relative to the car that are greater than the speed of the car relative to the ground. This faster moving air stream can be kept moving with a smooth underbody, and slowed back down by the diffuser so as not to cause a drag penalty.

Wooo, lots of theory, anyone can read books and make assumptions I said to myself ;) So it was time to experiment. The tool for accelerating the air would be an exaggerated one-sided venturi starting where a splitter would attach, and an underbody panel extending back to the front axle line. The front ground clearance at the splitter is 8.75", and the angle that the venturi makes with the splitter is 20 degrees at the start, curving on a large radius down to 5" off the ground over the course of about 10". The venturi is 57" wide, and the underbody panel extends about 22" back at the 5" height, with appropriate cutouts for the tires. From all classical looks, the car should 'flip over backwards at speed with that air-catcher I built.' ;) Negating the air that escapes out the side, when the car is traveling at 90 mph, the venturi is capable of accelerating the volume of air that passes under the splitter, 57" wide, to a stream traveling at 141 mph. This acceleration is caused by the drag associated with the increased frontal area (8.75" - 5") * 57" that the venturi has added. In my test calculations, this fast moving air stream has 587 square inches of area to affect, and an the 50 mph increase in air speed, along with the slowed air above the venturi, causes an average pressure decrease of .22 psi, for approximately 130 lb of downforce. The fast moving stream (although decelerating as it leaks out the sides) continues to affect the 22" of flat underbody. Assuming the speed drops off to 120 mph near the end of the underbody (this turned out to be an overestimate) I calculated an additional 150 lb of downforce from an average pressure differential of .29 psi and 515 square inches of area. Total projected downforce with no leakage in the venturi: 280 lb.

Test time! I constructed the venturi out of aluminum, for my Camaro, mounted a sensor to my suspension to measure deflection, and logged data at 12, 40, 60, 80, and 120 mph inn 3 configurations: no underbody panel, the venturi underbody, and with the venturi and a 5” splitter. The tests were performed back to back to back and over the same segments and lengths of ‘track.’ I averaged the suspension values over a minimum 7 seconds of travel, collecting data at 100 Hz, with the full suspension travel using about 10 bits of the 12 bit analog to digital range.
34184

The scale on the left is in data log units, with an increasing number meaning more lift. Both the venturi and venturi+splitter combo resulted in less lift than without. Neither combination resulted in a downward curvature of the lift to speed graph (that would have been awesome…) The addition of the splitter caused a drop in downforce. This is possibly because with it in place, the air above the splitter was being accelerated into the radiator opening and over the car, while the air under the splitter was not being accelerated yet. I believe that arguing that the venturi was too big and was ‘backing air up’ under the splitter would be an invalid argument based on compressibility. Moving the venturi start out to the leading edge of the splitter would be be the right move to make the splitter effective again, but I haven’t tried that yet. I run with no splitter instead ;) The results were 95 lb reduction of lift at 120 mph. At 2280 lb front weight, this only equates to an increase in lateral G capability of .04 G, but others can attest to how hard it is to get front downforce in a closed body car.

Very long story to get to my suggestion: The GTM has a much better underbody than my test Camaro, and much less front weight. Take advantage of the stage of bodywork you are in, and redesign the front to form the widest venturi, with a starting height of at least 50% higher than your smooth underbody ground clearance, to smoothly accelerate as much air under the car as you can. Take the drag penalty, it will be worth it for front downforce. (Then laugh at people who insist you car will fly up because you will ramp up on all the air you are sending under the car. :) ) Minimize the side leakages with skirts or vortices, and then move on to the difuser and rear wing to balance and assist bringing the fast air back down to free stream speeds. The underbody downforce will drop off faster once you are in the difuser section, so minimize the length without incuring too much angle. Too high of an angle creates unnecessary drag from flow separation. Don't rake the car too much, as it also slows down the air, increasing the pressure being exerted on the underbody proportionally.

(I'll edit and add a picture of the venturi tomorrow if I don't get killed for such a long post...)

crash

10-01-2014, 09:32 AM

Keith-Good write up. I have been working with your stated theories for years now in redesigning the underbody of the GTMR. It will be interesting to see the real world results.

fastthings

10-01-2014, 05:54 PM

Will someone read that for me?

kabacj

10-02-2014, 05:28 AM

Hey Keith

Great post. I had to think about it for a while but the concept makes sense. I have noticed the current crop of LeMans prototypes have the same "air catcher " splitter arrangement.

Makes total sense that if you can make the air go faster under the car then over the car you get downforce. Just like an airplane wing. The air goes faster over the top creating low pressure and lift. Reverse the concept with fast flowing air under the car and we have the holy grail of front downforce.

Seems that the wind tunnel agrees. All the new LeMans prototypes have splitters that force air under the car.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/b0a7acbebaed41ebef8371978387efbd_zpsfc9233fe.jpg

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/856291049004179483ee966a6e6ee4a7_zps547f742c.jpg

The gen 2 GTM already has a slot down the center of the splitter. All we need to do is optimize it.

http://i1073.photobucket.com/albums/w389/kabacj/001661d8-cedc-4d4e-8563-5f361f9a4591_zpsa835f48f.jpg

Great idea.

John

crash

10-02-2014, 08:54 AM

Will someone read that for me?

Simply put, if there is no airflow under the car, then no downforce can be made using the bottom of the car.

fastthings

10-02-2014, 10:28 AM

Simply put, if there is no airflow under the car, then no downforce can be made using the bottom of the car.
Awesome, thank you:)

kabacj

10-02-2014, 04:59 PM

Every weekend before a track weekend I have a punch list of items to work on to get the car ready.

The most important item this week was to adjust the oil pressure.

The pressure is adjusted using this nut and bolt.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/DA21F0AA-3B2E-4D35-8017-595EB601A5C8_zpsjanefsvb.jpg

On the GTM you will need to disconnect the pump from a the block because the adjustment on the ARE 4 stage pump is tucked into the motor mount.

All the lines remain connected so it's not a big deal. After stepping the pressure down two times I ran into a problem. Since I am screwing the adjuster out its getting longer.

The adjuster was hitting the motor mount. Oh man. An hour job just turned into a project.

Luckily believe it or not it's possible to get the motor mount out without even removing the headers. You just unbolt it from the block and frame and twist and turn it with the Pfadt lower section downward.

It took me a few minutes to get the right orientations but finally it came out. Almost like those metal ring puzzles when you get everything right they come apart easily.

After a few min with the carbide bit and die grinder I had cleared out a pocket for the adjustment screw.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/92099270-1BB8-4E5A-83C5-AAD42BDE08AB_zpsbqojiuul.jpg

Re installed everything and it all fit. Whew dodged a bullet.

I just need to adjust the toothed belt by moving the pump pulley 5/16ths of an inch back. That's when things went south.

crash

10-06-2014, 09:08 AM

I just need to adjust the toothed belt by moving the pump pulley 5/16ths of an inch back. That's when things went south.

Do tell.

kabacj

10-07-2014, 09:13 AM

After running the dry sump for two days at the track I saw that the front edge of the toothed belt was just barely touching the harmonic balancer. I could see some dust from the belt rubbing so clearly I needed to adjust the pulley back slightly so the belt would run without touching anything.

This job should take 30 seconds. ARE use a keyless drive bushing made by Fenner Drives.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/4a6ff01dd6d06dc67c9e9b681686df6b_zpsde54d654.jpg

It's very cool. It's basically an inner and outer set of wedges. When you torque down the nut the wedges expand and lock the drive pulley on to the pump.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/ea96aadeed9aad3557e3bd3d59a80ff8_zpsfab8268a.jpg

Unfortunately I had never used one of these keyless locking bushings before. It seemed to me that I would need to make it very tight in order to keep it from slipping. I had not done the research and found the proper torque for the drive.

Later I asked Gary at ARE. He suggests 14 ft lbs Fenner drives says 585 inch lbs. shockingly very little torque on the nut results in a very tight grip on the shaft and pulley.

All over the Fenner instructions it warns that over torquing the keyless bushing could result in damage to the bushing. Use a torque wrench!

Well needless to say I made the nut too tight. Probably 75 ft lbs. Now the bushing was locked on. There is not any room to use a puller with the pump installed. The pump needs to come out. I actually needed to drain all the oil from the system. Remove the 6 connections to the oil pump which was a messy job. Then I needed to rig up a way to press off the bushing without damaging the pump or drive pulley. Luckily I was able to grab the bushing with a bearing splitter and press the bearing off the same way you press off a pinion bearing. Boy when that thing locks on its a very tight press fit.

A few hours later I had the whole thing back together. I placed a call to Gary at ARE and he had a new bushing at my house the next day. 5 min after I had the new part the bushing was installed and belt re aligned .

I fired up the motor. Oil pressure was great. 60 psi cold at idle just like it was with the internal pump.

Since it was Tuesday and I was leaving Thursday I was happy that finally everything was working as it should.

crash

10-07-2014, 09:28 AM

I use the same style wedge fitting, but it uses four small allen screws to keep everything together. Your setup looks like it is more compact, but the advantages of the ones I use are that I can safety wire the locking bolts, and there are four alternate holes that are used by the locking screws to "unlock" the wedge arrangement. Built in press assembly, if you will. They get VERY tight in that there is a loud POP when the wedge separates. The down side is that I have to modify the ARE/JRP belt drive pulleys to accommodate the wedge lock.

kabacj

10-10-2014, 05:27 AM

I can safety wire the locking bolts, and there are four alternate holes that are used by the locking screws to "unlock" the wedge arrangement. Built in press assembly, if you will. .

That's a good idea. I am going to use those set screws as well. It's always better to have a belt and suspenders.

After sorting out the dry sump I was finally able to run the GTM around the track without any worries.

One of my setup goals for this weekend was to sort out the front rear grip balance.

Saturday I started running the Hoosier slick setup. I have 5 heat cycles on the tires that I did not scrub and let sit for a few days to cure. I did not get the most life out of them that's for sure.

Last time out I was loosing rear traction sooner making right hand turns then making left hand turns. I figured I had just over heated the left rear tire but I was not able to get good tire temps to confirm that in fact I was over heating the tire.

To even out wear on the tires I had swapped the tires left to right. To my surprise the traction issue followed the tire. Now I had rear grip issues making left hand turns! I guess I must have killed the left rear when running the tires on a mostly right hand turn track In only 5 heat cycles. That was not expected!

I am running soft compound up front and hard compound in the rear. This setup works well as it allows me to get heat into the fronts while getting some more life out of the rears. That was the plan anyway.

One thing I learned was that I needed to take rear camber out of the car when running the 355 rear slicks. Otherwise the inside edges over heat.

Even with the grip problems the slicks were still 2 seconds faster then the r888. I left them on until the rear was so loose I was fighting for control most of the time. I enjoy driving a loose car until I push things too far.

I eventually spun out. Of course it was in a 90 mph little quick left right chicane where I was not expecting the rear to break loose. Since I am nearly full throttle both rear tires spun up immediately. The rear snapped out 35 degrees to the right. I caught it but the car snapped back left so hard I could not stop it. Now I was along for the ride. At least I got the clutch in and was able to lock the tires so I kept going in the general direction I was traveling before I started spinning. I came out of the spin pointing generally down the track and drove off the track down the pit in exit.

Unfortunately the belly of the car went sideways across one of the curbs and grass and it just hooked the fiberglass that goes under the door sill. I never bothered to rivet the body to the frame under the door because it stays put without fasteners. That is of course unless you hook a curb going sideways at 90 mph.

A little fiberglass repair is needed but no big deal.
http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/F6D2360A-610D-424B-935A-003E951A76A0_zps9myvsthc.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/F6D2360A-610D-424B-935A-003E951A76A0_zps9myvsthc.jpg.html)

I was lucky not to damage my rims as I went through the grass. I did pickup some souvenirs however .

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/F02F6C6C-C03F-405A-A752-1E65ED97963E_zpstbbkhgoz.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/F02F6C6C-C03F-405A-A752-1E65ED97963E_zpstbbkhgoz.jpg.html)

I put the r888s back on and set the rear the rear anti roll bar to max from the softest setting I was running. With that change alone I cut my lap times by 1 second. I plan to add a stiffer rear anti roll bar over the winter. This mod really changes rear end feel especially when you are pulling +1g in corners.

john

crash

10-10-2014, 09:36 AM

All I'm going to say is that you are not alone in your tire observations. We have switched over to Yokohama slicks and couldn't be happier right now. Here is a video of Davy Jones running the PDG GTM at Sonoma on a previous tire that didn't work for us long term. Two seconds faster when the tires were new, but...

https://www.youtube.com/watch?v=rzs8vYKFspA

Those tires only had one 3 hour endurance race on them and you can see the difficulties he is having keeping the car under control. Working it hard. Since going to the Yokohamas it has been nothing but good things. Took us a few sessions to get the suspension setting correct, but our grip and tire wear is PHENOMINAL. Give Troy Simmons a call at Trackside Performance, 949-589-5394. Troy runs the North American Yokohama distribution facility, so you are dealing as direct with Yokohama as possible when you deal with him. I really think you will be happy you did. Tell him you are racing a GTM just like the Prototype Development Group GTM and he will send you exactly what we are running. We have been working with him and he also has our setup notes so either he or I can give you those. PM me if you would like the numbers.

kabacj

10-17-2014, 05:04 AM

Crash, thanks for the contact re the Yokohama tires. I will try them, the Bridgestone slicks and the Hoosier a6/r6 combo to see which work best and last the longest.

In addition to tires there are a few other upgrades I recommend.
Last trip to the track my buddy experienced rear bearing failure. This is a common thing on c5 corvettes that see lots of track duty. His c5 corvette has about 35k street miles and about 30 track days in the past 2 years.

When I upgraded everything from the c5, the bearings were one of the things I focused on.

I used these bearings.

http://www.skf.com/binary/12-157664/leaflet%20corvette_%20LETTER_size_tcm_12-157664.pdf

One of the best things about the GTM and the C5 is its possible to get parts quickly even at the track on a Saturday.

After 4 hours of track time on Friday the bearing failed. I convinced my buddy we could fix it. We had the new bearing from Napa in an hour and swapped it in another hour.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/CBA2B1B1-4814-48A3-80F6-488E6F9AAB08_zpsgnelha2i.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/CBA2B1B1-4814-48A3-80F6-488E6F9AAB08_zpsgnelha2i.jpg.html)

If you plan to track your GTM bearing upgrades are a good idea.

kabacj

11-03-2014, 10:31 AM

Now that I can take the car out of commission for a few months I can dig into the projects that take more then two weekends.

I am at the point where I am happy with the mechanical grip in slow speed corners. I have tuned out the front push which makes the car much safer to drive on the street. Going too hot into a corner with a car that pushes is much easier to control but of corse not as fast on the track.

The next frontier is aero grip and drag reduction.

While I was on the track I did some aero testing. In F1 they use a product called flow vis. It's like paint and it travels along the body of the car with the airflow.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/ac549cdfd55c6983814c04730a9127fb_zps85876dfa.jpg

I use this fancy thing called motor oil. I think it works almost as well on a matte black car.

The first thing I am going to do is completely shroud the front of the tires. This is a drag reduction step for top speed runs as well as an effort to smooth airflow around the car. While I am working on this area I will apply canards to the nose of the car. As a baseline I got a view of the airflow in this area

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/D1AB9B0C-0A01-4F52-B579-7C032D4E11EA_zpsyg1xecm9.png

The next item will be wheel arch vents. I did not expect the air to move across the hood so far in front of the windshield.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/84097198-88ce-4848-b669-dc2f2fff9d37_zpsbace5047.png

Also on the list is the roof scoop. again I was surprised that air was going across the roof instead of directly back.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/0DCD3C39-86B5-4984-AC69-5E868EBC8DE0_zpsmtqvorxk.png

I am going to checkout the race cars at SEMA if I can get any ideas before I start construction.

John

longislandwrx

11-04-2014, 12:02 PM

awesome info, have fun at SEMA.

kabacj

11-10-2014, 06:40 AM

Does anyone know what the light colored material is on the bottom of the splitter?

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/5145777D-004B-430C-A3C5-94A28BCD898A_zpsggkpaua0.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/5145777D-004B-430C-A3C5-94A28BCD898A_zpsggkpaua0.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/64A7928A-C1D7-4D9F-B309-48DF220FF1FF_zpsov82wprj.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/64A7928A-C1D7-4D9F-B309-48DF220FF1FF_zpsov82wprj.jpg.html)

One of the great things about SEMA is you can inspect factory race cars. You would never be able to get this access at the track.

John

fastthings

11-10-2014, 08:09 AM

Fraser D

11-10-2014, 08:32 AM

Does anyone know what the light colored material is on the bottom of the splitter?

John

John,

Phenolic cotton cloth laminated sheet.
Be very careful machining or cutting this product from a HSE view point. Basically treat it like fiberglass from a dust perspective but when I was machining it we had to be careful of the fumes released from the resin.
They may have changed the resin by now.
Great stuff for making gears etc so I am not surprised that it is being used as a wear strip.

http://insulations.en.ec21.com/Phenolic_Cotton_Cloth_Laminated_Sheets--3816538.html

kabacj

11-10-2014, 05:50 PM

John,

Phenolic cotton cloth laminated sheet.
Great stuff for making gears etc so I am not surprised that it is being used as a wear strip.

http://insulations.en.ec21.com/Phenolic_Cotton_Cloth_Laminated_Sheets--3816538.html

Great! Thanks Dave.

Since my splitter took a heavy toll this season from both impact and abrasion. One goal will be to make it wear better, but also balance the ability for it to break away without destroying the front body work.

John

kabacj

11-10-2014, 06:01 PM

Not sure, but I met a guy over here that has a line on the rod ends, for the A-arms. He calls them a Johnny joint. Also he may make a replacement for the c5 a-arms, possibly in kit form.

Knowing you, you probably allready know about him. artmorrison.com

I saw he had a GT Sport patch on his bag and started a conversation with him. He lives over by me and never knew. He makes lots of cool stuff.

Hey Gene.

Unless I missed it Art Morrison does not have a direct application that would work for us using the c5 running gear. I am still looking for a solution at a reasonable price but it's starting to look like I'll just need to make my own. I am not looking forward to machining the three parts needed 16 times.

John

Fraser D

11-10-2014, 06:12 PM

Probably cheaper than a replacement CF splitter from FF5
FYI I have a Gen 2 unit if you need one from their attic sale.
Cheap-Cheap!

JCHRacer

11-10-2014, 06:27 PM

Jab-rock wood or a composite called Tegris are commonly used by lots of racecar constructors. Both are highly abrasion resistant but as you noted, the most difficult thing is designing the rub material to break away without destroying the bodywork. It's almost like you want to mount the rub plane directly to the chassis and let the bodywork float on a separate mounting system.

kabacj

11-11-2014, 06:09 AM

It's almost like you want to mount the rub plane directly to the chassis and let the bodywork float on a separate mounting system.

Hey Joel thanks for the additional materials. Yes I agree. I was thinking of making the nose undertray of from several pieces of aluminum or foam core fiberglass This way each section could tear away without ripping off the whole thing. Then mount the splitter as another piece so it also could break off without causing a DNF.

The other way to go is to make the splitter super strong. I have seen several races where the splitter blasts through dirt like a shovel covering the car with dirt as it plows along un damaged. Or during endurance race pit stops the pit crew stand on the splitter when cleaning the windshield.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B4E275D9-2FC3-4A50-82F1-E6E7DED609BA_zpskkhcfcmo.jpg

It's much easier to make the prices weak enough to break away but still strong enough to support the aero loads. The strong design is something to think about.

John

crash

11-11-2014, 08:59 AM

We use plywood coated with resin. Pretty strong, very cheap.

fastthings

11-11-2014, 11:32 AM

I have to think, the additional pieces are there to skid off the ground and wear away, rather than a layer of break off parts. I think it needs to be rigid, you could design a crumple zone.
So know where does it crumple? You could let the whole bonnet pop, not likely. You could design a zone in the front bars, unhinged, not likely.

Slice the nose, down low below the lights threw the grill, the attach it with something that would give under impact. The problem with that is now when you out plowing for potato's and the splitter digs in
you have a catapult for your front tires, and no steering.

I vote for solid as a rock and hope you don't hit something.

Can't wait to see what you do. Cool stuff.

crash

11-11-2014, 12:27 PM

fastthings

11-11-2014, 01:10 PM

FYI our entire nose box that includes the radiator and splitter is removable and is considered the "crumple zone". The splitter is separately attached to the nose box, but it is rigid. You can kinda see in this pic how the splitter is attached. There is a framework UNDER the plywood as well that supports the skirt.

I was just thinking out loud, I have no relevance, and not referring to your car.

He will come up with something cool that I'm sure others will copy.

crash

11-11-2014, 01:22 PM

I was just thinking out loud, I have no relevance, and not referring to your car.

He will come up with something cool that I'm sure others will copy.

Sorry if it came across the wrong way. I was trying to say that you had the same idea that we have been using and it works very well. Great minds think alike. :)

Fraser D

11-11-2014, 01:44 PM

I currently have a bit of a hybrid version.
My splitter tray is mounted to the chassis which tucks up inside the hood nose and the original CF FF5 splitter attaches to the hood.
Now that I have separated the nose from the hood itself I will convert to more in line with what the PDG car has as a set up.

kabacj

11-11-2014, 08:08 PM

We use plywood coated with resin. Pretty strong, very cheap.

Crash. no shame in plywood. Balsa wood core is still used in production cars, let alone one off race cars. I want to try to emulate my fabrication heros with fancy composites, but still keep the basic convenience of a tilt hood via the factory five design. And most importantly have a venturi under the nose to increase down force. Not sure if it can be done, but I will try.

I vote for solid as a rock and hope you don't hit something.

Gene, there is merit to the design where you make the splitter stand up to everything but a tire wall. A foam core with a composite skin will allow for both the freedom to have a complex three dimensional design splitter and under tray , but still be reasonably light and definitely something that can be reproduced so i can have a few spares.

I currently have a bit of a hybrid version.
My splitter tray is mounted to the chassis which tucks up inside the hood nose and the original CF FF5 splitter attaches to the hood.
Now that I have separated the nose from the hood itself I will convert to more in line with what the PDG car has as a set up.

Dave I think this is the way to go.

Crash thanks for showing how PDG have the front under tray setup. I think what you guys have done is the right design. I might replace some of the solid struts with rod ends on aluminum struts, but in the big scheme of things thats just a nice to have and really does not impact the performance of the car. The only reason I would not use the solid flat bottom setup is the inability to contour the plywood to allow for a slot under the front of the car.

I think we all agree that a design that looks like this

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/856291049004179483ee966a6e6ee4a7_zps547f742c.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/856291049004179483ee966a6e6ee4a7_zps547f742c.jpg.h tml)

is best to force air under the front of the car to increase air speed and generate down force.

Speaking with folks who have done testing of the GTM and cars with similar shape in the wind tunnel. Little changes like the amount of air going under the splitter/ out of the diffuser can make a massive difference in the total down force of the car.

IF i am lucky I will have a few designs to test on the track and maybe even in the wind tunnel.

John

crash

11-12-2014, 10:41 AM

Just keep in mind that just about every design you see out there is not usually a performance maximized design, but rather a performance maximized design given a particular set of rules. The splitter on the DP car is a great example.

kabacj

11-12-2014, 11:43 AM

Taz Rules

11-12-2014, 06:12 PM

Great point. I actually focus on what the rules prohibit. Usually prohibited thing works well :)
Hmmmm....I should try using that line on my wife. :cool: :o

kabacj

11-12-2014, 09:35 PM

Hmmmm....I should try using that line on my wife. :cool: :o

Ha ha. Yeah. When you read the IMSA rule book everything they prohibit in a DP car would give you a significant advantage.

Many of the things mentioned like adaptive suspension or torque vectoring differentials are out of our league.

But building big splitters and venting the front wheel wells are things we can do.

The Factory five 818 is a baby GTM from an aero perspective.

One thing that has worked well is venting the wheel wells out of the side of the door.

The gtm is setup to do this as well with a little sheet metal and Fiberglass work.

Look at how the c7r does it.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B7A8A48E-297F-451A-9DD6-B07F87A065CE_zpsrdpjlvat.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/B7A8A48E-297F-451A-9DD6-B07F87A065CE_zpsrdpjlvat.jpg.html)

Note no fender arch vents.

This mod is on my list as well.

John

Fraser D

11-12-2014, 10:30 PM

Ha ha. Yeah. When you read the IMSA rule book everything they prohibit in a DP car would give you a significant advantage.

Many of the things mentioned like adaptive suspension or torque vectoring differentials are out of our league.

But building big splitters and venting the front wheel wells are things we can do.

The Factory five 818 is a baby GTM from an aero perspective.

One thing that has worked well is venting the wheel wells out of the side of the door.

The gtm is setup to do this as well with a little sheet metal and Fiberglass work.

Look at how the c7r does it.

Note no fender arch vents.

This mod is on my list as well.

John

John,

Your reading my dam mind again!!! ;-)

fastthings

11-13-2014, 08:31 AM

If you have no rules, I could see you designing a variable wing.
Any mounting, linkage would be easy for you. Sourcing the parts, for you, easy.
From there, tap it into a simple computer, speed inputs, brake inputs.

I like the C7R mod, that is going to be sick, I can't believe that hasn't been done yet.

crash

11-13-2014, 09:43 AM

I like the C7R mod, that is going to be sick, I can't believe that hasn't been done yet.

Again, because we have already. :)

You can kind of see what we have done on the number 4 car in that flying picture. And then, of course, there is my interpretation...:)

kabacj

11-19-2014, 06:06 PM

In addition to the aero projects, I am tuning the suspension over the winter.

I found that more rear anti roll bar made the car handle better as I added more. I also have the rear shocks adjusted to full stiff both on compression and rebound.

The consensus is I need stiffer rear springs. The stock setup I'm running was intended for use on the street with street tires. It's actually pretty amazing that I was able to run the stock rear setup to this level of grip. Now it's holding me back.

So out come my dampers to be revalved for 20% stiffer springs. Maybe I'll install 4 way adjustable valves too as its an easy upgrade.

While working back there I think I an going to swap out my poly bushings for a spherical bearing kit. Seems like all the race teams go to spherical control arm bearings to get more accurate wheel control (camber,caster and toe) as well as more feel through the chassis. Of course this only matters at the limit on the track but I still don't have the same contact patch feel I learned to expect racing GP motorcycle. Maybe it's impossible to get that level of feel in a car but I figure stiffer is better.

Anybody have recommendations on,or experience with spherical bearings in a GTM or corvette?

With pfadt out of business LG motorsports seem to be the only game in town.

Thanks.

John

fastthings

11-20-2014, 09:05 AM

I'm real curios how the comp and rebound effect things. My guess is I think you will find the edge, with bigger sway bar, stiffer springs, which is good.
Is that how you ran your bike, stiff comp and stiff rebound in the rear? In the woods, I found it best with stiff comp and loose rebound at the rear.

http://www.artmorrison.com/2006cat/2014catalog.pdf, page 25 he has what he calls a Johny Joint. Not sure if that's what you need.

crash

11-20-2014, 11:56 AM

kabacj

11-20-2014, 07:48 PM

We also just went stiffer on valving, springs, and rear bar. It was better.

We have purposely left the urethane bushings because we are not sure that the frame can handle the solid mounting and, well, we hit things during our long races.

Hey Mike

Good to know we are going in the same direction.

It does make sense that keeping the poly bushings would allow for some compliance to avoid bending or breaking parts if you rub or bump off of another car. Regarding the frame I am pretty sure the front is strong enough as I have beefed that up somewhat already when I added more structure to the cage and foot box. Of course when you guys are running 25 hours at a clip and you add lots of oscillation loads you will find the weak points.

I discussed adding the spherical bearings with Jim Schenk at SEMA. The 818r is running with spherical bearings using the same construction methods . Of course not the same frame. My gut says that after adding a few gussets for good measure, the fame will be fine. We will see however. I do not push any part of the frame as hard as you do in the 25 hour. I'll test it for a season. If I don't have problems maybe it will be an improvement you and Richard can add to the 25 hr car.

I'm real curios how the comp and rebound effect things. My guess is I think you will find the edge, with bigger sway bar, stiffer springs, which is good.
Is that how you ran your bike, stiff comp and stiff rebound in the rear? In the woods, I found it best with stiff comp and loose rebound at the rear.

http://www.artmorrison.com/2006cat/2014catalog.pdf, page 25 he has what he calls a Johny Joint. Not sure if that's what you need.
Hi Gene

I never liked an ultra stiff setup on the bike, but rather I like to be on the stiffer side just before the point where I would start to lose grip over rough or rippled pavement. I am pretty sure the setup does not translate between bikes and cars, but I am sure that when the suspension is too soft, I get too much weight transfer on both bike and car. On a bike you can compensate by shifting your body weight forward or back, not so much in the car.

I am very much a novice when setting up the car, but the GTM chassis is so stiff I can very easily feel one click of compression or rebound in the front or rear. That’s really cool. A stiff chassis makes it easier to tune the car since when you change a spring or damping setting you only have that change impacting the setup of the car. Where if you have a flexible car you are tuning to the car flex as well as the suspension compliance.

I think the art Morrison stuff is geared to their chassis instead of the c5 stuff we run. same idea however.

mikespms

11-21-2014, 09:18 AM

http://store.pfadtracing.com/c5-corvette-suspension/

Hey John,

Here is a link to Pfadt Racing, It looks like they are back in business.

kabacj

11-21-2014, 03:15 PM

http://store.pfadtracing.com/c5-corvette-suspension/

Hey John,

Here is a link to Pfadt Racing, It looks like they are back in business.

Hey Mike. Thanks. Looks like their web site still works but nobody is home. I gave them a call to see if they were in fact back in business and had inventory. Their number is out of service. I know they were at SEMA but I did not stop in to talk with them. I want to make sure they have what I need in stock before I order from them. Thanks for the heads up however.
John

mikespms

12-01-2014, 01:46 PM

kabacj

12-01-2014, 08:34 PM

Hey John,

There is a new number on the Pfadt web site, they changed ownership and are reorganizing.I left a message and got a reply from Steve at this number 951-493-7100 I am looking for a set of motor mounts and asked him about spherical bushings, he said he was going to check inventory and call me back.

Mike

Thanks Mike.

I was sorry to see that Pfadt went under as they sold very good products. Unfortunately sometimes it takes more then good products to succeed. But maybe now they resurface with some experience and a new plan. I hope it all works out. Let us know what you find out. I use their motor mounts and poly suspension and am very happy with no complaints.

John

mikespms

12-02-2014, 12:04 PM

Hey John,

I got a return call today and they have some inventory,I ordered the motor mounts and should get them in a few days. If you need anything call Mark @ 951-493-7108 he said that if they don't have it they should go back in production in a month or so.

Mike

KeithBoden

12-02-2014, 04:31 PM

I'm surprised that the ends of the A-arms haven't been cut off and replaced with some beautifully tigged 3/4" bore aluminum rod ends already ;) It doesn't make replacement as easy as obtaining another C5 arm if you break one, but let me know if you want to fabricate arms and I can give you a Solidworks file with the dimensions. I made a set of lower arms on a strut car out of 1.25" x .110 mild steel, with 5/8" bore Summit brand rod ends. After 25,000 miles on the road, and a few hundred on the track, they are still doing fine. I even hit a curb once hard enough to bend the tubing - the rod end stayed intact.

http://thefactoryfiveforum.com/showthread.php?4045-What-did-you-do-on-your-GTM-today&p=149491&viewfull=1#post149491

kabacj

12-02-2014, 06:18 PM

I'm surprised that the ends of the A-arms haven't been cut off and replaced with some beautifully tigged 3/4" bore aluminum rod ends already ;)

http://thefactoryfiveforum.com/showthread.php?4045-What-did-you-do-on-your-GTM-today&p=149491&viewfull=1#post149491

Well Keith. Don't think I didnt consider modifying the A arms. Welding on the aluminum of the stock A arms would remove the heat treating. Maybe this would be fine but maybe not. A better route is to go with what you have done and fabricate arms. Nice job by the way. My dream solution would be to mill up billet arms like those used by the factory sponsored corvette race teams.

After all the dreaming I always come back to the same conclusion. Paying the price for a setup that easily fits into the stock c5 arms is actually the cheapest and by far the fastest most reliable solution.

Now don't get me wrong I would love to modify the stock units but I'm entering into uncharted territory there and for very little if any gain vs just retro fitting the stock setup with spherical bearings off the shelf.

I think in a future phase of the GTM development I will try my hand at fabrication like you did.

Right now I need to focus on getting ready for next year. I have a busy race schedule planned for next year starting in March. That's right around the corner! I am stressed already :)

Right now, I want to focus on the aero ideas you kindly outlined in detail. Rebuild everything that wears out. Setup the car for stiffer springs and a selection of anti roll bars. Tire pressure and temperature monitoring. And a few body mods that should make the car more slippery as well as closer to finished.

My goal is seat time. Lots of hours on the track will keep me busy maintaining the car. Since I am a one man team. Any place where I can use proven tested solutions will lower my workload next year.

I know you went through the exercise of measuring and building CAD drawings. Are you planning on building your own A arms for your GTM?

John

kabacj

12-22-2014, 06:33 AM

After spending several weekends putting natural gas heat in the garage then organizing the tools and supplies that have accumulated over the course of the build it was time to get some fabrication done.

When the sequential transaxle arrives from Mendiola it comes with a shifter that you modify to your application.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/8FEADA3B-7464-43A6-ABF0-C6D68DCFCEC4_zpsoy3ux5ww.jpg

I was so happy with the five speed mendiola transaxle I wanted to keep as many of the aspects of the setup as possible. One thing I tried to replicate was the shifter position and mounting location. If you are familiar with the shifter sold with the factory five kit the base has 4 mounting points one on each corner.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/e9a03964e40ae949507442f01620d4cc_zpsda632262.jpg

I needed to create a simple and quick solution to adapt the mendiola shifter. Turned out some angle iron got the job done. I have used this setup for the past year.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B9ECB144-8CA4-4352-9B26-BFFC417A64E6_zpsnya2fppe.jpg

Now I want to move the shifter three inches forward. It will make for a slightly more comfortable driving position. I decided to mount the shifter to the tunnel frame instead of the Toyota shifter mount.

First I cut the metal that would span the tunnel. Then I cut and mounted two tabs to the shifter. The shifter has nuts welded on so assembly is a one wrench operation. I hate using two wrenches.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/18D87A08-2872-44CD-AFF0-D2D4504A1AC5_zpstbvncvmm.jpg

Finally I cut off the old mounts positioned the shifter and welded it in place.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/94BA6BE6-2D25-44C2-A9F5-AD97011ADEFF_zpsya8m5t8r.jpg

With a tab in the back the shifter is amazingly rigid.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/1A0FE22F-5BE6-4610-9787-292AB6A123B8_zpssoaxluqt.jpg

The next job is re routing the shifter cables.

John

fastthings

12-22-2014, 11:33 AM

Hey man, hows it goin. What do you use to cut that metal for those brackets, nice clean cuts.
I have never used a tig, are you using it for the steel also? I need to buy some tools!

kabacj

12-22-2014, 04:26 PM

Hey man, hows it goin. What do you use to cut that metal for those brackets, nice clean cuts.
I have never used a tig, are you using it for the steel also? I need to buy some tools!

Hi Gene.

I make most of my cuts with a 4x6 horizontal/ vertical band saw. The inside and outside cuts are cleaned up on a stationary sander or with a grinder.

Low tech and slow but it gets the job done.

Yep I tig everything. Tig gives you total control of the weld. Again it's slow, but the results are good. Yeah get some tools! You will want to modify even more than you already do!

John

fastthings

12-22-2014, 05:33 PM

I need a band saw, do you have a metal brake?

kabacj

12-22-2014, 05:46 PM

I need a band saw, do you have a metal brake?

Yes I have a metal brake, a lathe and a drill press. With exception to milled parts I can pretty much get what I need done.

Except for the TIG welder many of the tools were purchased used. Most times a well taken care of machine that is 60 years old is better then the new stuff built today at least for the money. When you get used tools you can afford a pro quality tool that is cheaper then a new hobbiest tool.

kabacj

12-29-2014, 09:57 AM

So two days of work and I am finally done reconfiguring my shifter and cables. This is exactly why I did not do this during the race season. I knew I would spend a couple of days making everything work they way I wanted.. and also I did not have the proper length cables or the time to get the job done right. I just made the cables I already had for the five speed Mendiola work.

In order to deal with the cables that were too short, I got a length of 1/4 28 threaded rod and a coupler and extended the shift rod. Of course this also required me to relocate the mount point for the cable on the transaxle.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B965DADF-7286-4155-A841-C8DF22C0BE54_zpsdsm97gvi.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/B965DADF-7286-4155-A841-C8DF22C0BE54_zpsdsm97gvi.jpg.html)

I made the aluminum bracket as stiff as I could but it still flexed slightly when I shifted gears. Not ideal but It worked for several races and track days.

The proper way to mount the shift cable on the transaxle looks like this.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/EB0CCF8F-231D-4C00-9A16-6B86985427F5_zpsrc7duuwn.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/EB0CCF8F-231D-4C00-9A16-6B86985427F5_zpsrc7duuwn.jpg.html)

As you can see much shorter and as a result stiffer.

Now on the drivers side of the cable I needed to modify the sequential shifter that came with the transaxle so it fit in the GTM. My quick and dirty fix for that looked like this.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B9ECB144-8CA4-4352-9B26-BFFC417A64E6_zpsnya2fppe.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/B9ECB144-8CA4-4352-9B26-BFFC417A64E6_zpsnya2fppe.jpg.html)

Now that I had the time I wanted to move the shifter more forward. (Impossible before as the cables were not long enough). The new position allowed me to mount the cables to the shift body in such a way as their was minimal flex.

The first go round I had the cables mounted to the shifter like this.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/8679B32B-B70B-4656-92BD-5CC4D0B5474C_zpsmaafg34g.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/8679B32B-B70B-4656-92BD-5CC4D0B5474C_zpsmaafg34g.jpg.html)

This allowed for the cables that were too short and the lack of space behind the shifter in the GTM center tunnel.

Now that I had both room behind the shifter in the tunnel and the proper length cables I moved the mount points back.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/362D1E73-2B97-4BB5-AA42-D553EBE99691_zpspz6us4gr.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/362D1E73-2B97-4BB5-AA42-D553EBE99691_zpspz6us4gr.jpg.html)

I also welded them together so they are much stiffer. They form a V shape which is far stiffer then a square welded to a flat surface and the lower bracket has a triangular brace attached to the shifter body again for stiffness.

The final result below.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/8FA65A3B-69C7-4A12-B25E-F23F4A18EA4F_zpshfyzyhwm.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/8FA65A3B-69C7-4A12-B25E-F23F4A18EA4F_zpshfyzyhwm.jpg.html)

I installed it and tested it out. The shifts are much more positive now. Lots of work for something that barely looks different, but it was worth it.

John

johngeorge

12-29-2014, 01:10 PM

no lift shift? sequential?

kabacj

12-29-2014, 01:48 PM

no lift shift? sequential?

Yes sir. And the ability to swap ratios at the track.

johngeorge

12-29-2014, 02:09 PM

sickness.. you crazy kinda guy!! love it

fastthings

12-30-2014, 09:22 AM

sickness.. you crazy kinda guy!! love it

So do I, love it.

You need to come to my house, I'll take you to my track. This is in my back yard.
http://youtu.be/QImTZYnv-wI

kabacj

12-30-2014, 04:48 PM

So do I, love it.

You need to come to my house, I'll take you to my track. This is in my back yard.

Gene this track is the perfect place to take your GTM. 1/2 mile long straight will have you up around 155 and all those twists and turns are going to be awesome. The GTM is a great car to cruise around in on the street but if you really want to see what it can do the track is the only place.

Can't wait to hear how you like it.

John

kabacj

01-04-2015, 08:36 PM

The past few weekends have been spent taking care of all the little things that don't stop me from racing, but I really wanted to get done. Things like pulling the unused AC lines and condenser out.

With those things done I started on the modifications to the under body panels. When I installed the dry sump I installed the remote oil filter in the cavity between the drivers side rear wheel and the engine. I left the underbody close out panel off so I could keep an eye on everything and check for leaks. Now that I am happy with the setup I wanted to replace the panel. Drilling out 25 rivets every time I needed to check in that area or change the oil filter was not going to happen.

I did some searching and found this solution to add 1/4 turn fasteners.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/850FFD94-238C-488D-9A5D-0C1FC412232A_zpsguohdy6b.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/850FFD94-238C-488D-9A5D-0C1FC412232A_zpsguohdy6b.jpg.html)

This way 5 fasteners and the panel is off. Quick and easy. I forgot how cool these things are.

I welded in the plates then I needed to locate the holes on the panel.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/22BCBB79-B327-4AEB-95FD-5B011CE99AB3_zpsdyiudl4e.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/22BCBB79-B327-4AEB-95FD-5B011CE99AB3_zpsdyiudl4e.jpg.html)

Sure they sell tools for this , but I forgot to get one. I also figured I could do one better then the off the shelf tool. I lathed up this little tool out of a scrap dowel. Note the little green O ring I added.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/5AB68F23-0761-4CEC-9FDB-0A2468D2A508_zpsrelj4ufo.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/5AB68F23-0761-4CEC-9FDB-0A2468D2A508_zpsrelj4ufo.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/4007CC60-AC33-4D80-A122-02DB31475173_zpsflqbpyqf.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/4007CC60-AC33-4D80-A122-02DB31475173_zpsflqbpyqf.jpg.html)

It fits right into the plate and stays put while I install the panel and tap it with a hammer to make nice dimple in the aluminum sheet. The off the shelf tool would fall out working under the car. I drilled the holes and installed the buttons.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/9A9A93ED-878D-4321-A831-0A89B2123E21_zpsphpyoi3b.jpg

I like this solution so much I am installing the panels under the engine accessory drive, the panel I made for under the motor, and the diffuser with the same setup.

John

kabacj

01-19-2015, 09:17 AM

I have between working on small projects and learning how to vacuum form composite parts over the past few days. While doing that, I made a quick and easy upgrade everyone with a willwood brake / clutch pedal set can use.

Setting the brake proportion front to rear in requires moving the balance bar on the pedal assembly. Sure you can climb under the dash and make the adjustment, but doing that 10 times in a row as you slowly creep up on the ideal front to rear brake bias is a drag.

I personally only made a few adjustments and called it good. If I could adjust the bias on the fly I would use the bias as a way to setup the car for the conditions and grip each day.

Now with this setup from Wilwood 340-4990 Remote Brake Bias Adjuster Cable bias changes will be easy.
http://i1073.photobucket.com/albums/w389/kabacj/04dc4625-2851-4150-9dd4-26b4074fc0df_zps06ac66df.png (http://s1073.photobucket.com/user/kabacj/media/04dc4625-2851-4150-9dd4-26b4074fc0df_zps06ac66df.png.html)

The install is quick even on a completed car.

You just simply thread the nut on the end of the adjuster on to the balance bar and snug up the lock nut.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/52CB483E-1D88-4A4A-BCEE-4C96320266AE_zpsqiwcdips.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/52CB483E-1D88-4A4A-BCEE-4C96320266AE_zpsqiwcdips.jpg.html)

Here is a shot of the cable that twists the balance bar.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/53176D59-FF47-44C7-B8D3-FBC7EAB3E7D9_zps5mrdrodz.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/53176D59-FF47-44C7-B8D3-FBC7EAB3E7D9_zps5mrdrodz.jpg.html)
and here is the knob that connects to the cable

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/A609D896-13EA-4F0B-AEF9-965FD986FB21_zpsjeyetgte.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/A609D896-13EA-4F0B-AEF9-965FD986FB21_zpsjeyetgte.jpg.html)

All I need to do is mold my console cover to finish the install. Adding the knob under the dash or by the seat on the floor is also an option.

kabacj

02-04-2015, 07:58 PM

NASA did a promo this summer and although I did not have my racing license yet I got a few cameo milliseconds in the video.

It's a well done video. See if you can spot the factory five cars

http://www.youtube.com/watch?v=N3MxZZVtU4o&sns=em

buffalojr

02-05-2015, 08:14 AM

After watching it like 4 times, found the GTM at 0:47.

crash

02-05-2015, 01:13 PM

Pretty cool video. I hope NASA does more of this stuff in the future.

kabacj

02-05-2015, 08:35 PM

Pretty cool video. I hope NASA does more of this stuff in the future.

Yep I agree Crash. Very good publicity for NASA. It makes you want to try it out.

After watching it like 4 times, found the GTM at 0:47.

Buffalo, when you look at this car as much as I have its ingrained into your psyche. When I watched this video the first time I did not even know I made the video. The few flashes of the car I was like wait a second. Was that my car?

here are the shots where factory five cars made the video.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/gtm1_zpsqyrt5vlb.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/gtm1_zpsqyrt5vlb.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/gtm2_zpsst5nwdql.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/gtm2_zpsst5nwdql.jpg.html)

and here Pat McMhan with is modified cobra.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/gtm3_zpsf1d7hepn.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/gtm3_zpsf1d7hepn.jpg.html)

I love racing with NASA. Its a great organization. If you are not into wheel to wheel racing, they have HPDE and time trials which get you out on the track without the pressure of racing.

If you try it you will be hooked :)

John

kabacj

03-01-2015, 06:35 PM

I hope to make a trip down to Virginia International Speedway the third weekend in March, so its time to wrap up the winter projects.

Last year I mounted the power shut off switch in the cockpit.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B19FFA64-1A38-4623-9839-3C3B834EE2A1_zpscphgjf6l.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/B19FFA64-1A38-4623-9839-3C3B834EE2A1_zpscphgjf6l.jpg.html)

It was an easy spot to mount the switch and I did not have the time to do any fabrication. I always wanted to use a cable operated switch because that would mean a shorter path for the power to get from the battery to the starter, and less total wiring.

I decided the best place to mount the switch was on top of the battery, but that means I needed to do some fabrication. Its great because at this point in the build I have tons of scraps so I can just use them to make the parts I need.

After making paper templates and lots of head scratching, I cut out the parts in aluminum.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/235a204f-94a1-407b-828f-9febcd97d487_zpsbgwda8se.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/235a204f-94a1-407b-828f-9febcd97d487_zpsbgwda8se.jpg.html)

Next a little bit of welding to put all the parts together. They turned out to be very strong as i had hoped.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/0F866B7D-7451-455C-851A-9DE6CB79F66F_zpslanp6wwa.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/0F866B7D-7451-455C-851A-9DE6CB79F66F_zpslanp6wwa.jpg.html)

Then a test fit. Its really tight in there so I hope it all still fits now that its welded.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/09EB6CD4-B8CF-4EDD-BF5A-EC0B2930AA88_zps67npjoc6.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/09EB6CD4-B8CF-4EDD-BF5A-EC0B2930AA88_zps67npjoc6.jpg.html)

After a little testing I was able to route the cable so the pull to switch the power off is very easy with very little effort lost in the cable path.

I am sure the high quality bicycle cables helped make the pull smooth.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/ADEE1764-AEE7-43C4-AC68-2BA5EA7A9412_zpsd8o83etu.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/ADEE1764-AEE7-43C4-AC68-2BA5EA7A9412_zpsd8o83etu.jpg.html)

Finally I made a loop in the cable and added some red covering after I took the photo I added some heat shrink tubing over the fitting that holds the wire loop to prevent the allen screw from backing out and prevent the metal from wearing the paint if it touches.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/9DF27270-2EAC-4350-81F6-F5249D28815B_zps1me9ni2e.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/9DF27270-2EAC-4350-81F6-F5249D28815B_zps1me9ni2e.jpg.html)

Lots of work to make a simple improvement but I am happy with how it turned out.

John

longislandwrx

03-02-2015, 06:59 AM

A lot of work but it sure beats shoveling snow.

looks great!

kabacj

03-02-2015, 12:25 PM

A lot of work but it sure beats shoveling snow.

looks great!

Funny you should mention shoveling snow. One of my biggest problems for the trip to VA is getting my trailer out of storage. It's trapped in and blockaded by the snow and ice. It's going to take a few hours or maybe a tractor just to get it free.

I hope it warms up quickly!

longislandwrx

03-02-2015, 03:22 PM

Tell me about it, I made the mistake of not clearing 100% of the snow in a small section of my driveway during ONE of the storms. Its now a 3" thick block of ice. I won't see asphalt for a month.

kabacj

03-03-2015, 10:07 PM

Its time to kick things into high gear as my things to do list is always longer than my time available to work on the car.

A whole box of GTM goodies arrived from Performance Shock today.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/8FFE3473-C4C0-4A04-905C-79E1061B3FA7_zpsrd5jjmjk.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/8FFE3473-C4C0-4A04-905C-79E1061B3FA7_zpsrd5jjmjk.jpg.html)

The shocks have been rebuilt and revalved to increase the damping rates allowing me more adjustment in the range I tend to use on the track.

In addition to the rebuilt shocks I also got an assortment of springs .

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/11C702AD-4245-4A2F-9850-46E41EC96025_zpstzgqgl2b.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/11C702AD-4245-4A2F-9850-46E41EC96025_zpstzgqgl2b.jpg.html)

I am going up to 650 on the front and have 800 and 900 lb springs to try on the rear. I was trying to support the car with the anti roll bars and damping rates and I think the stiffer springs will allow me to use the damping and anti roll bars to fine tune the car instead of control the weight of the car.

and finally I got an assortment of bump rubbers.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/39C938B7-3288-4A7F-A904-4C99462DEFC9_zps1rh1ooco.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/39C938B7-3288-4A7F-A904-4C99462DEFC9_zps1rh1ooco.jpg.html)

The bump rubbers allow you to fine tune the motion of the wheel in compression. The Bump rubbers effectively create a rising rate spring that you can fine tune. Thats why I have so many hardness bump rubbers to try.

If I lived on the West coast Performance shock would allow me to use their shock dyno to verify the setup. Their shop is right outside Sonoma Raceway. For now ill just try them out on the track but later in the season Ill try to get out there and get some hard data.

John

johngeorge

03-04-2015, 09:10 AM

kabacj

03-04-2015, 01:50 PM

John, I have and use spring rubbers to make quick adjustments at the track with spring rates, you shove them in the middle of the spring coil. I do have a bunch with me if you want to try them out at VIR March just let me know.
http://d163axztg8am2h.cloudfront.net/static/img/45/de/e1eb47c05cb544426f91f1f8034f.jpg
http://www.steelerubber.com/2-5-inch-coil-over-spring-rubber

Hey John. Yes definitely. I've never used them before but they sound like a great tuning tool. I'm really looking fwd to driving VIR. It's the fastest track I have visited yet.

Thanks!

crash

03-04-2015, 03:30 PM

Hey John. Yes definitely. I've never used them before but they sound like a great tuning tool. I'm really looking fwd to driving VIR. It's the fastest track I have visited yet.

Thanks!

I know you are probably aware, but beware the grass! High speed and grass equals lots of $$.

kabacj

03-04-2015, 05:51 PM

I know you are probably aware, but beware the grass! High speed and grass equals lots of $$.

Very true Crash when you leave pavement at 100+ the grass barely slows you down.

However, I prefer grass to a track like LimeRock where you are hemmed in by walls a few feet off the pavement in nearly every turn. Go off there and you do real damage every time.

This will be my first time at VIR so I don't intend to set any track records. Just get familiar with the layout and find a good setup

So far I have not had the opportunity to air it out in fifth.
The strait following the oak tree turn should be my first chance to do that with the Mendiola S5R sequential geared to pull hard at the 4->5 shift at 150. We will see how it goes.

With better aero, more grip, and with stiffer suspension the whole setup should be better, but we will see about that.
John

kabacj

03-06-2015, 05:58 AM

UPS man left some fun stuff at my house last night.

My rear tires and rims arrived. Unfortunately they were not at the same warehouse so getting them mounted and balanced would cost me valuable time. It's possible they would have arrived in time, but missing tires would ruin my race weekend so I was not willing to chance it.

It's a sad sight when your race tires arrive and are covered in snow.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/5AAA5C73-16F5-4A1A-B6CB-BB21ED202440_zpsnk4mldvl.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/5AAA5C73-16F5-4A1A-B6CB-BB21ED202440_zpsnk4mldvl.jpg.html)

Light weight and strong rear rims
http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/00B6C117-EA28-4078-B73C-D5F4FAFA2715_zpsrkuywfou.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/00B6C117-EA28-4078-B73C-D5F4FAFA2715_zpsrkuywfou.jpg.html)

John

crash

03-06-2015, 09:55 AM

Just a heads up, both the recent tire manufacturers that we have used said that their race slicks COULD NOT be subjected to freezing conditions without adverse detrimental effects occurring to the tires. Also, if the temperature is at all not warm, then handling of the tires is also critical to avoid damage. In other words, we had some small sidewall cracks on a couple of the tires that we were worried about and the manufacturer said that that was common when people throw or drop tires in cold weather. After he mentioned it I did see and recognize how the dealer reps handled the tires. They always roll or place them as opposed to tossing them. :)

Those look like they may be DOTs so probably not as sensitive, just be aware.

kabacj

03-06-2015, 01:06 PM

[QUOTE=crash;190944]Just a heads up, both the recent tire manufacturers that we have used said that their race slicks COULD NOT be subjected to freezing conditions without adverse detrimental effects occurring to the tires. Also, if the temperature is at all not warm, then handling of the tires is also critical to avoid damage.

Those look like they may be DOTs so probably not as sensitive, just be aware.[/QUOTE

Yep DOT tires this time.

Good advice Crash. I have heard the same. I went with the Hoosier A7s front and R7 rear this time to try that combo out.

The Yokohamas are next month. Hopefully it will be above freezing.

John

fuggles

03-06-2015, 01:36 PM

The strait following the oak tree turn should be my first chance to do that with the Mendiola S5R sequential geared to pull hard at the 4->5 shift at 150. We will see how it goes.
John

Hi John, Do you have the standard ratios or custom? For the standard ratios with 3.55 final drive, looks like 5th gear is not useful. I was thinking about going with the 4.11 final drive to be a bit quicker (but possiblty more shifting).
Are you happy with the ratios or would you make any changes?

Kent

kabacj

03-06-2015, 04:43 PM

Hi John, Do you have the standard ratios or custom? For the standard ratios with 3.55 final drive, looks like 5th gear is not useful. I was thinking about going with the 4.11 final drive to be a bit quicker (but possiblty more shifting).
Are you happy with the ratios or would you make any changes?

Kent

Hey Kent,

Fifth gear is not “useful” on a track where I am going no more than 150 . However my motor has 550 ft lbs of torque. And I find that running slightly taller gearing makes it easier to avoid spinning up the tires constantly and also is less work rowing the gear box . Sometimes grabbing another gear for a few seconds gains you very little. When you just spin up the tires is not worth much at all. Note that I can still spin up the tires pretty easily with the tall gears so I don’t want to make that easier.

I think more importantly if you are very serious about matching the ratio of the gear you pull out onto the longest strait and other important corners on the track you really need to plot your gear and power curve to the track and optimize for the most important ratios.

For example the SDR which is geared taller allowed me to run out 4th gear to 156 where I need to shift the Sequential on the same strait. A few mph don’t really gain you much for a second or so and I just back off a little so I don’t bounce off the rev limiter.

However on a track like Road America , COTA or Daytona you are going to exceed 150 and then its great to have fifth which on my transaxle is a little shorter than the SDR.

I also wanted a gear that I could pull to 200 mph bc I think it will be cool to go that fast and want to try.

I have lots of experience gearing a very high strung 125 GP bike where I had a box full of sprockets to get just the right gear to match the narrow power band in all the right corners. In my view its better to have an easy to drive taller gear setup as long as you have plenty of torque. It does depend on the tracks you drive. Mendiola will make you gears if you need them so I figured go with the taller setup as I liked the SDR. (The H pattern 5 speed)

I would not change the setup if you offered me the option to change to 4.11 gears for free.

I know team PDG run the 4.11 gears in the S5R and they also seem to be happy with that setup. Crash can chime in on what he thinks about the pros and cons. The LS motor really helps your transaxle choice. Its such a flexible power plant you cant go wrong.

crash

03-06-2015, 05:08 PM

And that is the beauty of these cars. The amount of TORQUE per pound of vehicle. Yes we run the 4:11 in the S5RR. I worked with Ian quite a bit to get the ratios right the first time. All went pretty well with the exception of the initial 2nd to 3rd split. 2nd was technically the right gear for the very slow corners we saw on the tight tracks like Button Willow, and 3rd was the correct gear for the low speed corners at Thunderhill, but the split between the two was too much. We raised the 2nd gear by 1 or 2 teeth(can't remember now) and it is now just about perfect. We can't run over about 160-170, but we don't have the tracks here to do that anyway...at least not with our 550 HP.

We tuned the gear box to run at both BW and TH without changing gears between races and are very happy with the results. Not optimal for Laguna or Sears, but we run many more, and more important races at BW and TH so that is what we geared for.

It really is great to be able to change a gear ratio by one or two teeth depending upon the requirements. You would be hard pressed to find another gear box that you could do this with...especially at the price point of the Mendeola.

fuggles

03-08-2015, 02:55 PM

Thanks for the comments guys.

I am familiar with the idea of tuning gears for the longest straight. Back in my karting days we would do this with the rear sprocket. Also we could tune the clutch engagement for corner exit.

For the car, I do not expect to have the skills or funds to tune the gearing for the track. I am trying to balance street fun, maybe some auto-x, and track days. Tracks would be Sears Point, Laguna Seca, Thunderhill and maybe Buttonwillow. I like the idea of running the 4.11 with its quickness. Sacrificing top end. I'm not so sure how it will work in practice.

Unfortunately I can't optimize for everything! :) So I value your opinion about what you have done and how it works.

Thanks,
Kent

kabacj

03-10-2015, 06:43 PM

Some VERY cool new carbon fiber parts arrived on my door step today.

Just in time for install over the weekend before I head out to Virginia International Raceway.

A new splitter to replace the one I destroyed last year and new Canards hot off the presses.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/98BD1F55-AC23-4C7A-9842-8D9725590E20_zpsgcr1pzng.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/98BD1F55-AC23-4C7A-9842-8D9725590E20_zpsgcr1pzng.jpg.html)

The new splitter is VERY nice. Too nice to take out on the track with all the rocks and flying stuff, but maybe this one will last a little longer.

Courtesy of the 818 production factory five were able to outsource the Carbon Fiber splitters for the GTM and boy are they nice!.

Perfect vacuum molded parts. No voids and very light.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/5E1471F5-D723-4BFD-8469-B3E0C0441099_zpsz6m7lphz.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/5E1471F5-D723-4BFD-8469-B3E0C0441099_zpsz6m7lphz.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/38C7B70D-31B2-4593-8E83-85E817F681AD_zpsda7tzriy.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/38C7B70D-31B2-4593-8E83-85E817F681AD_zpsda7tzriy.jpg.html)

Hot off the presses are a set of Canards that fit right over the details on the GTM Body.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/A7F37432-5D53-4BCE-BFF6-B6224B1C1DAA_zps7pdvrhza.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/A7F37432-5D53-4BCE-BFF6-B6224B1C1DAA_zps7pdvrhza.jpg.html)

Made to be trimmed to fit the theme of your car.Notice the traced line as a suggestion of the finished shape. I am going to keep them full size for max down force for now.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/7649825B-6561-4D81-BF3C-C98D8F8D208B_zpsx3yqalnr.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/7649825B-6561-4D81-BF3C-C98D8F8D208B_zpsx3yqalnr.jpg.html)

Woo hoo. I love carbon parts!

Presto51

03-11-2015, 05:55 AM

John pretty cool parts but have to ask.

You finally found something you can't make? :p

What are your dates for VIR?

Ron

kabacj

03-11-2015, 06:36 AM

John pretty cool parts but have to ask.

You finally found something you can't make? :p

What are your dates for VIR?

Ron

Ha ha. Well I am actually in process of making a few carbon fiber parts. The factory five parts are great quality and although I love to make things I need to focus my time on the things that I can't buy as nobody makes them.

More to come on that in the next few weeks.

My current plan for VIR is to leave early thurs the 19th and arrive at the track late afternoon. Then roll out of there early as possible on Sunday afternoon for the drive home.

Maybe I'll see you there?

Presto51

03-11-2015, 10:59 AM

John let me check with my CFO about making the trip down there. Sounds like it will be fun

Ron

The Stig

03-11-2015, 06:38 PM

Hi John,

I've been a "lurker" on your thread for quite some time. And i have to say that I've been impressed every step of the way. You've brought a ton of innovation to the build of your GTM. It's really fun to keep up with.

And beyond the obvious build skills that you've shown us, it's extremely cool to watch you hone your race skills as well. When I read the line about you taking the Oak Tree turn shifting from 4th and pulling hard theough 150 mph into 5th, all I could do was grin at the thought of it. I get to race vicariously through your endeavors. Keep up the coolness Dude!!! ��

It reminds me quite a bit of our friend Dave Borden... ��

kabacj

03-11-2015, 08:43 PM

Thank you Mike for the kind words.

I was watching the early stages of your build when i decided to purchase a GTM. Your willingness to share your experience building allowed me to see what a build is really like as well as get ideas for my build. Thank you for that.

I think we all love to see each other go through the build process. Dave B, Hugo, Mike in fla, Gene , Tino, yours , and Eric and Mr Andreson getting started. Every build has great personal touches.

You are going to have a great time driving your car in Cali. It has really turned out well. You think you get attention on the forum here, Just wait till you are out in public!

Now that you are nearly done. What are you going to build next! :)

The Stig

03-11-2015, 09:38 PM

Now that you are nearly done. What are you going to build next! :)

That one is still up in the air. I have about 4 different cars that I would like to build at some point. Not sure which one will be first, might be at this point.

I've always liked the shape of the FFR Type 65, and Dave's making the Mk-IV look like a great idea also.

A 62 Corvette resto-rod would be pretty cool also...

But I'd like to enjoy my GTM for a while first. :cool:

Mike

mikespms

03-12-2015, 07:44 AM

Hey John,

Check the link to the APR performance site http://aprperformance.com/racing-vehicle/factory-five-gtm/

kabacj

03-12-2015, 06:41 PM

Hey John,

Check the link to the APR performance site http://aprperformance.com/racing-vehicle/factory-five-gtm/

Thanks for the link Mike.

I think APR might need to add a new picture because this just showed up on my door step!

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/311FCCDA-4C6E-4988-A38D-879CCD479D73_zpsug0yfvvk.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/311FCCDA-4C6E-4988-A38D-879CCD479D73_zpsug0yfvvk.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B4A56CC5-375C-4F59-AF98-6F47F9317A4F_zpsj2cpgu8a.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/B4A56CC5-375C-4F59-AF98-6F47F9317A4F_zpsj2cpgu8a.jpg.html)

72 inches of double element down force producing awesomeness! This wing will make up to 1600 lbs of down force at 160. That will be enough!

Since aero tuning is my goal this year I figured having tons of tuneable low drag downforce would be a good start! Cant wait to try this baby out.

John

kabacj

03-14-2015, 08:15 AM

Last season I had the CV bolts loosen up. Prior to that I meticulously prepared the CV bolts and never had an issue, but after not having an issue I figured I was over killing the process so I just tightened things up and they did not stay tight for long.

The process that works without issue.

1) Install the CVs using RTV or your goop of choice to seal the CV joint to the transaxle or outer stub axle and the CV boot holder to the CV joint. Tighten to spec. I use 35 ft lbs or so. Your torque may vary depending on the hardware you use.
2)after the RTV is dry remove 3 of the 6 bolts. Scrub out the grease and RTV out of the threads. Then using a Q-tip. Clean the threads in the transaxle or sub axle. Add red locktite and retighten. Then do the other 3 bolts.
3) mark the bolts so you can see if they have loosened without putting a wrench on them.
4) look at the back of the flange on the transaxle / stub axle to make sure the bolts are not sticking out. If so grind them down a bit when you pull them out to clean them. I have had to remove 1/16 an inch on some bolts as they hit the bolts attached to the hub on the upright.

This process worked 100% of the time without failure.

At the track I don't have time for this process so i decided to drill and safety wire the bolts. This way its a one step install without wait then safety wire and im golden.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/64D1D8B7-2A5C-4D9E-ACEF-49A4E55A930F_zpsd5jmsed1.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/64D1D8B7-2A5C-4D9E-ACEF-49A4E55A930F_zpsd5jmsed1.jpg.html)

John

kabacj

03-16-2015, 05:54 PM

Spent the last few days prepping for my first race of 2015

I re aligned the car and set the toe.

I am going with -3/16 on each side up front and rear toe at - 1/4 on each side.

I also dialed out a bit of rear camber going with -.09 left rear and -.08 right rear .

I reset the ride height to allow for .04 degrees of rake. According to recent articles in race car engineering. A flat floor car like the GTM can create significant downforce using just the underside of the car.

The rake in the car moves the downforce bias forward which is very important. Notice how the pressure is lower under the front of the raked car

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/958e86a7-6b53-4089-bd31-3f4ed7819f0c_zpsbojwsgfb.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/958e86a7-6b53-4089-bd31-3f4ed7819f0c_zpsbojwsgfb.jpg.html)

I hope this condition is even more pronounced now that I have covered up the opening under the engine.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/50417598-CB46-40CE-B613-12BCF271F0F3_zpsl3fj5v7g.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/50417598-CB46-40CE-B613-12BCF271F0F3_zpsl3fj5v7g.jpg.html)

I just need to install the 1/4 turn fasteners at the rear of the engine cover sheet aluminum and that's done.

crash

03-17-2015, 09:37 AM

carbon fiber

03-17-2015, 11:00 AM

kabacj

03-17-2015, 11:48 AM

As I have posted before, the GTM is very sensitive to rake. What is your difference in frame heights front to rear at the axle center lines?

Also, I think you are going a bit overboard with a total of 1/2" toe in in the rear. Don't be surprised if the car "fights" itself. Also, from our experiences, it may be very uncomfortable going down the straights at a good speed with that much toe in, so take it slow at first.

Take it slow? Ha ha ha.
Just kidding.

Good point. Speeds will be higher for longer. I'll take 1/8 out of both sides in the rear.

I run a bit more castor then you guys if I remember correctly but with the speed less toe might also be a plus.

I use a long acre digital angle guage to verify the rake on the frame rails but I'll measure.

kabacj

03-17-2015, 12:21 PM

Thanks again for sharing all this info John. You're paving the way for all of us who want to get the most out of our setups. I'm looking forward to seeing how these changes will affect the car. Good luck at the track.

My pleasure.

I keep a log of all the changes I make now, but I have been checking the thread to see what I did and how it worked too.

We all share what we know and what we learn and we all end up with better cars. It's a win win.

Presto51

03-21-2015, 08:43 PM

Saw John and his GTM in race mode.

Great guy, great car, great time. :cool:

I'll let John fill in the blanks, until then I'll throw a couple of pictures at you

Ron

kabacj

03-23-2015, 05:37 PM

It was a great race weekend at VIR.

I had the pleasure of meeting Ron. We had a great dinner at the restaurant at the track. Which serves the best food I have ever eaten at a track. It would be a good restaurant in a big city. Unexpected way in the county at a racetrack.

I also met a few our factory five brothers who drive the challenge series.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/082226E3-D1C7-4FAA-AC2B-54972E8D3A24_zpsvwpqphfo.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/082226E3-D1C7-4FAA-AC2B-54972E8D3A24_zpsvwpqphfo.jpg.html)

It's great pitting with folks who share the build experience and love racing.

When i was not bench racing I was wrenching on the car while talking to people. I literally could not stand near the car without being asked what is that. Who makes it. How much hp does it have. Who makes the motor. How long did it take to build.

I love to talk to people, but when you are trying to subtract fractions in your head setting the toe or any other task that requires focus and considering you are trying to get it all done quickly so you can get back out on the track. it can be difficult :)

A few things you can learn from.

I mounted the diffuser. And tested the airflow using oil drips. It seems to flow much like predicted in the simulations

http://i1073.photobucket.com/albums/w389/kabacj/AA30BBB0-9F02-4FA0-84F6-C0AB0F3CF2A8_zpsyuataqxu.jpg (http://s1073.photobucket.com/user/kabacj/media/AA30BBB0-9F02-4FA0-84F6-C0AB0F3CF2A8_zpsyuataqxu.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/65D77BFD-8A9C-42A4-B5C9-94EF92819762_zpseiu64yxh.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/65D77BFD-8A9C-42A4-B5C9-94EF92819762_zpseiu64yxh.jpg.html)

Now I need strakes and to close up the transaxle clearance hole.
I wanted to test clearance going in and out of the trailer before I made strakes. Those will be ready next time.

The other thing that happened that you all can learn from

I somehow got a big hole in my cv boot during the race. I guess it was a rock. But after the hole cv grease was flung all over the passenger side of the engine compartment.

My last laps were pretty smokey in the cockpit but I didn't realize It was cv grease. I figured it was just a bit of oil on the exhaust. I need to Lower my oil pressure again as the long full throttle high RPM sections were causing oil to blow by the main seal.

After 2 hours of cleanup. I resealed the cv flange ( that's where I thought the grease was escaping) is cleaned and lock tite all the bolts .

The next AM I Went out for my first run. More smoke. Now I knew it was leaking again. Since the bearing still had grease on it after running a race with a holy boot I figured I'll just stay out here till the session is done.

I need to add a split cv boot to the spares kit. Removing the cv boot takes too long as a quick track repair. Anybody know of one that fits a 930 cv?

Ideally I'd get the one that bolts together.

Thanks
John

fastthings

03-24-2015, 07:46 AM

Cool, any video of the 150+ runs? Did you race, or was it a track day? Did you like your alignment canges? Who did you want to keep up with, and did you do it?

Fun stuff keep it up John

crash

03-24-2015, 09:29 AM

I have plenty of CV boots like the one you sent me a picture of. They can be found here...http://www.myraceshop.com/930_CVs.html

Just click on the "add to cart" button above the $10.95 price on the right. That is for the one piece GKN boot like you have. Apparently I forgot to get a picture up there of that. I will do that ASAP.

On another note, if you are using the Bel Ray recommended grease very little should come out, even with a hole in the boot. We used to have big problems with grease liquefying and coming out of the boots, but not after switching to the Bel Ray. Are you using that grease?

We actually end up swapping out to spare axles almost exclusively due to boot issues now. With the good internals and the right grease we get over 50 hours of run time on the axles and CVs before we replace them out of caution. That equals all of the 25 hour race, and then we repack the CVs and run an entire season of endurance races without needing to service them with the exception of when/if a boot is damaged. You may want to think about carrying at least one spare, ready to go, axle assembly with you to the track.

kabacj

03-24-2015, 02:51 PM

I have plenty of CV boots like the one you sent me a picture of. They can be found here...http://www.myraceshop.com/930_CVs.html

Just click on the "add to cart" button above the $10.95 price on the right. That is for the one piece GKN boot like you have. Apparently I forgot to get a picture up there of that. I will do that ASAP..

Thanks I placed the order. Great part and great price.

On another note, if you are using the Bel Ray recommended grease very little should come out, even with a hole in the boot. We used to have big problems with grease liquefying and coming out of the boots, but not after switching to the Bel Ray. Are you using that grease? ..

I do use the Bel Ray, and that kept the CV well lubed while some of the extra grease I put in the boot sprayed out

We actually end up swapping out to spare axles almost exclusively due to boot issues now. With the good internals and the right grease we get over 50 hours of run time on the axles and CVs before we replace them out of caution. That equals all of the 25 hour race, and then we repack the CVs and run an entire season of endurance races without needing to service them with the exception of when/if a boot is damaged. You may want to think about carrying at least one spare, ready to go, axle assembly with you to the track.

Good idea. I do have all the spares, I probably should store them assembled. This was a freak thing where a rock punctured the boot but next time I will just be able to pull out one assembly and mount the other.

Thanks for the advice.

John

kabacj

03-24-2015, 08:10 PM

Cool, any video of the 150+ runs? Did you race, or was it a track day? Did you like your alignment canges? Who did you want to keep up with, and did you do it?

Fun stuff keep it up John

Hi Gene,

Yep i did grab some video of 150+. Unfortunately I was hampered by my oil pressure. On shorter tracks I never see the extended high RPM running that I do quite a bit of at VIR. As a result anything over 5500 RPM i was blowing oil out the rear main seal. Kind of annoying, but since lowering the pressure on my dry sump is an involved job I just short shifted.

I did make many alignment changes. The alignment that I liked best was -1/16 of total toe in up front and - 3/8 of total toe in out back. I am going to work on setting up the car with more caster as well as attempting to tune the bump steer.

The new wing was great and I also really liked the 800 lb springs in the rear.

It was a race weekend. VIR is a long and complicated track to learn. I hope to get back there in May for more track time.

I will find some video and post it.

Plebeian

03-24-2015, 10:05 PM

May I ask what times you were running at VIR?

kabacj

03-25-2015, 05:41 AM

May I ask what times you were running at VIR?

Hi Plebeian

Unfortunately I was not able to turn any fast laps this weekend. The combination of my oil pressure issues with my dry sump pump set at too high pressure spraying oil on the exhaust if I ran above 5000 rpm. The hole in my CV boot during the race Saturday smoking up the cabin and nearly getting me black flagged then taking me out of contention on Sunday. Then the setup and adjustments I needed to make to my new cable shift setup and all of the alignment changes I was making on Saturday held me back.

This was a test and tune weekend where I had hoped I had guessed correctly on all my winter changes. Some were great. Like the stiffer spring rates and revalved shocks. Some were wrong like the aggressive toe. I made good progress but I'm not there yet.

This is a reality forum. :) sometimes things go well and we have storybook results. Some times Lady Luck has something against us and we get blanked. I would not enjoy this if it was easy :).

Based on the times set by guys I run with normally I should be setting times around 2.00 flat.

I want to get back to VIR in May for hyper fest. We are going to need to wait for that to see what the GTM can do.

fastthings

03-25-2015, 07:44 AM

kabacj

03-25-2015, 05:33 PM

If you wouldn't mind, could you describe the difference in the feel you got from the toe changes. Also what so you think the stiffer rear spring did for you, I think you did it to keep the car from compressing the shock so much. Did it give you a different feel, enterence or exit?

Messy weekend, life in the fast lane. Your a fun guy, I know that didn't bother you a bit.:)

Ha I'd rather have everything go like clockwork, but I make mistakes and things happen. So I need to fix them that part is fun.

Lets start with a giant disclaimer. I have found that every setting you make on a GTM changes how the car feels at speed. We will call “at speed” to be +100mph. I know from talking to lots of guys who build factory five cars that many of us do a “quick alignment” oh that looks about right.. and go out and drive. Nothing wrong with that until you start going fast on a track or a top speed run at a sanctioned event.

Then your car that was fine to dive at 70mph on the highway picks up some weird handling behavior that people make up reasons to describe. Unlike buying an OEM factory built sports car and hopping it up and going as fast as you can. Factory Five give you a GTM setup for the street, developing the GTM for racing conditions just like the paint and assembly is up to you. If you want to drive your GTM at high speed under racing conditions you need to setup the car for that purpose. Team PDG did that. I am learning how to do that. Hopefully we can make it easier if you want to do a bit of this yourself. Every setting is important and relates to the others. If you are driving on the street at speeds that will not get you thrown in jail you will be fine with the setup from the manual. OK with that said.

I was going to change the toe at home based on Crashes experience and recommendation , but I ran out of time getting everything packed for my first trip to the track.

I went out for my first run with -3/16 on each side up front and rear toe at - 1/4 on each side I progressively took toe out of the front till I stopped at - 1/16 of total toe in.

As you take toe out of the car it changes direction even more quickly. It also feels like it tracks around the radius of corners a bit better. I was happy with the front so I left it alone and started changing the rear toe.

As I removed rear toe, I think I started feeling bump steer. I set my bump steer before I ever drove the car. I also did not know the ride height that I should tune the bump steer around . I plan on measuring and resetting the bump steer at my current ride height.
The changes in how the car felt were not drastic as I removed rear toe in, but I ended up most happy with – ½ inch of total toe. Note that under 130 mph the difference between -1/2 and -1/4 of total toe was not as large as the decrease in toe up front.

The stiffer springs:

The stiffer spring and stiffer damping package benefit weight transfer. The setup I was running last year did not have enough control of body roll and front to rear weight transfer. I left this change to the experts at Performance Shock who recommended changes based on the motion ratios of the suspension and my feedback.
I was locking the front inside tire on decreasing radius turns like turn 1 at Lime Rock and I had to wait an extra heartbeat for the car to settle after making very sharp low speed chicane type turn . Unless you are running the exact same anti roll bar package, shock damping settings the springs are not going to get the same behavior, but it makes sense that factory five sell the gtm with a spring package that is firm but not harsh.

How does it feel with the stiffer setup?

I have more front grip and less body roll. Both good things. The tracks I run on are pretty smooth, so I didn't notice that the ride was more harsh.

It's fun to change how the car behaves using these tuning tools. Since you are almost done with your car you can spend weeks tuning your setup to your use case and what you like or just set it up like the manual suggests and drive it. For the street either way works and both are fun.

John

mikespms

03-25-2015, 09:10 PM

kabacj

03-26-2015, 05:11 AM

Hey John,
Thanks for sharing your experience and results it is very helpful. How is your rear tire wear with that much toe,did you check tire temps?
Waiting for the new track video if not just the sound track.
Mike

Hi Mike. I do get noticeable tire wear in the middle inside of the contact patch from the toe setting. The wear is not significant enough to be a problem however since the tires heat cycle to the point that grip is gone before they wear out.

I did not check tire temps this weekend because Friday the track was damp and Saturday I was chasing other things.

I have scheduled 2 test days last week in April to spend more time on the alignment setup as well as suspension and aero tuning.

I think 1/2 inch of total toe is a bit too much. It feels good, but I also think that if I reset the bump steer around my current ride height I may be able to back the rear toe out. For those of you that are new to bump steer it's how the toe changes as the wheel travels up or down from ride height.

My goal is to get 1/16th of total toe in per inch of compression in the rear and 1/32 of toe out per inch of compression up front from bump steer.

I plan to view my video this weekend. Hopefully I can find some good bits. I will also document the alignment and what settings I had and what I change them to.

John

fastthings

03-26-2015, 08:21 AM

Thanks for doing all that typing John, I do alot of suspension tuning with a simulator, so I like hearing what people feel from a susp change. I completly understand your disclaimer about driving at speeds, versus highyway driving. I live in a real cool place, lots of places to go nuts. This car will be capable of killing me at any givin moment. It must be tuned to drive on country roads at speed, very dangerous. And I do live 10 minutes from a 2.5 mile road corse. It will be a long learning curve, but what ever, I'm looking forward to it.
Sounds like the rear bump steer continues to be an issue, and like you say one thing affects another. I wonder, does the 1/2 inch of rear toe feel good because it nolonger bump steers, the bad part about too much rear toe would be temps, and maybe a little too loose into the corners.

kabacj

03-26-2015, 09:14 AM

and like you say one thing affects another. I wonder, does the 1/2 inch of rear toe feel good because it nolonger bump steers, the bad part about too much rear toe would be temps, and maybe a little too loose into the corners.

Yep. I'm not sure why I like 1/2 inch of total toe better than 1/4 in the rear, but I am sure that since I did not purposefully set the bump steer it's probably not optimal. That's why I am getting the right tools and doing the setup properly.

I have not had trouble with tire temps or the car getting loose so it's not a major deal. I am probably giving up some grip and we don't want to do that :)

John

fastthings

03-26-2015, 10:35 AM

Well, what your doing is really cool, I wish you lived over my way.

kabacj

03-26-2015, 04:53 PM

Well, what your doing is really cool, I wish you lived over my way.

Gene I think I would rather live by you. With all those beautiful smooth roads (not covered with crater sized potholes)and that great track around the corner you have the best of both worlds for a GTM.

You are going to need to have the nose of your hood wrapped with chip guard however. I would hate to see that beautiful black paint ruined on the racetrack. In one year the nose of my car started turning red as there were more chips than painted area. The other area that gets chipped is the rocker area in front of the rear tire.

kabacj

03-31-2015, 04:54 PM

Working on improving my setup with the new shock and spring package. I very happy with the stiffer springs and added additional damping each run trying to limit the number of changes I was making per run.

I was getting excited that I had some newfound grip in the first session on Sunday am. With ambient temps around 45 and dew off line the track was a little challenging.

Last lap I decided to run it in a bit deeper. Well I got a little off line and lots of under steer. I was clearly not making it around the corner but I wanted to slow as much as possible before I left the track. All ended well as I did not ruin my new splitter.

On the down side I locked up the inside front tire a bit too long. It's a very soft compound .

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/DBD435FD-5D4D-4340-92F7-DDDA7C17A2A4_zpslzmrmob0.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/DBD435FD-5D4D-4340-92F7-DDDA7C17A2A4_zpslzmrmob0.jpg.html)

I finished another lap on the tire and it was ok but low speed it had a nice thump thump.

Ok fine I can't use it for the track, but I wanted to try an auto cross. Should be fine for that. Not going too quickly and nothing to hit. On further inspection I think it's junk.
http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/256A70DE-04DF-43A4-B4D5-8401FD43EDF9_zpsneekn39a.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/256A70DE-04DF-43A4-B4D5-8401FD43EDF9_zpsneekn39a.jpg.html)

There is a soft spot/ bubble. Man that sucks. Oh well at least the other tire is still new with only one heat cycle . I can replace the flat spotted tire and the tires should have similar life.

fastthings

04-01-2015, 07:34 AM

kabacj

04-01-2015, 09:42 AM

I have not tested mine yet, I hope I can dial up too much rear bias.

Have you been able to get your brakes to lock up front or rear, lock to lock, with your adjuster? I wonder if you will be dialing in a little more rear bias, because of that. I love it that you share the bad with the good. Ken Block would have grabed his E-brake.:)

Hi Gene,

Race car development is not easy. Especially since I have never done it before I will make lots of mistakes. I learn the most when I make mistakes so I think you all should learn with me.

I did not get to adjust my brakes this time at the track. My fronts lock first and have for most of the time I have been taking it to the track. Front lock up is better in the rain. I can out break most folks pretty easily so I have not spent much time getting the most out of the system. However I am sure I can make the car easier to drive and brake even harder if I get everything setup just right.

I am going through the registration process so I can work on things like brake balance on the street both in the dry and the wet. I will get adjustments in the ball park then do the fine tuning at the track where aero and other factors are in play.

The Willwood pedals and manual adjuster do not have a massive range of adjustment. It seems like we will need to set the major adjustment using the threaded rods that push down on the master cylinders then use the Willwood cable adjuster and the balance bar to tune the balance front to rear. I will report back on how that goes.

Its far easier to deal with a car that locks the front tires first. In the past I have had the rear bias such that I could rotate the car using the brakes. That was interesting, but I backed off from doing that since I figured it would be better to err on the side of caution until I get other major systems setup the way I wanted.

I'll let you know how it works out.

John

crash

04-01-2015, 10:22 AM

Maybe just personal preference, but the guys always set the PDG GTM up so that it goes out with too much rear brake. I simply can't stand a pushy car, so I will usually end up turning in about 2-3 turns of front brake during the first session.

Again, the nice thing is that the adjustments do work and the car is pretty sensitive to them.

kabacj

04-01-2015, 05:11 PM

Again, the nice thing is that the adjustments do work and the car is pretty sensitive to them.

Speaking of how responsive the GTM is to adjustments. When I was changing front and rear toe at the track I was surprised how different the car feels with minor toe changes.

That got me thinking about how I never really set the bump steer after I got the GTM on the track.

I figured I would measure by disconnecting the shocks and using a jack and toe plates to cycle the car through the full suspension travel.

The problem I had was taking measurements by myself I got a little too much variation. I needed a better way so i got this tool. I love tools!

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/FA8E5CF6-06DA-42BD-8DB9-F3C20EA2AA78_zpssx4uv5pf.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/FA8E5CF6-06DA-42BD-8DB9-F3C20EA2AA78_zpssx4uv5pf.jpg.html)

With this guy I can measure to the nearest 10,000th of an inch. That's far more than we need for alignment, but that's ok. I love precision measurements.

Turns out I have too much bump steer.

You can see in the graph I get over 1/32 of change per inch of suspension travel 1/32 inch of change is the upper limit. I need to try to reduce it.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/FD2536E8-E2A0-46D8-8530-D5CF317FE33F_zps1tuaqerc.png (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/FD2536E8-E2A0-46D8-8530-D5CF317FE33F_zps1tuaqerc.png.html)

This is just one wheel. I'm going make sure both wheels are the same. Then start adjusting.

John

crash

04-02-2015, 11:24 AM

As I have mentioned before, chassis setup is a DYNAMIC thing. Once you understand what is happening, then you can make static changes and understand what effects those changes are having, but first you must get everything setup the way it needs to be dynamically. This is good that you are going down this path. It is a requirement for making the GTM work at speed.

If you would like another "tool" I can not recommend highly enough the purchase of Suspension Analyzer from Performance Trends. The most significant part of this program that I use is the fact that it is a DYNAMIC program that shows you how everything interacts with each other. It is one of my secrets to building cars correctly...but I guess not a secret anymore! :)

http://performancetrends.com/SuspAnzr.htm

kabacj

04-02-2015, 11:46 AM

fastthings

04-03-2015, 08:01 AM

That is a cool tool John, I should get one. I know damn well I would pay that much in labor for someone to set up all four corners.
How do you mark ride hight with the wheel off, seems like with the wheel off it would be hard to know exactly where 0 is. Is it a guess, do you measure from the body? And we know that from 0, full up and full down is not a useable range. How much travel are you allowing for up and down before you quit trying to solve a bump steer condition.

I also wonder if I need to get some corner scales, have you set corner weights yet. I think I need to do this first. These are kind of spendy thoough.

mikespms

04-03-2015, 09:13 AM

Hey Gene,
I have an inexpensive bump steer gauge I got from speedway motors,It works good I Was able to get the front bump steer very close to zero about .005" in 3" of travel .Here is a link to the instructionshttp://static.speedwaymotors.com/pdf/910-82700.pdf . Since you have to unload the springs to set the bump steer the scales and corner weight get done after your alignment and ride height is set.

John,

I've been replacing my upper control arm and playing with the alignment but before I finalize the alignment I am going to check and set the rear bump steer. It is recommended to set your bump steer so that it toes out if you can't eliminate it. Bump steer kits for c5 corvettes cost about $200.00 the front kit should work on the rear.http://www.summitracing.com/parts/bae-3302001/overview/year/2003/make/chevrolet/model/corvette

kabacj

04-03-2015, 09:26 AM

That is a cool tool John, I should get one. I know damn well I would pay that much in labor for someone to set up all four corners.

The Cheap way to do this:

at ride height measure from the tire sidewall to the body. I put a line on the sidewall and body with a sliver sharpie so I could have to exact points to measure to.
Remove or disconnect the shocks put the wheels back on then using a jack under the car lower the car back to ride height.

I was able to put the jack under the transaxle so I could still run the tape measures under the car without them hitting the jack. I have the beefy transaxle mount i made so not sure how well this would work with the standard one. if its a problem just rig up the jack so you can still lift the car from the center line keeping it level side to side but not have it in the way of the tape measures.
Take toe measurements every 1/4 inch. Lots of measurements will average out any error you get from the tapes and toe plates.

How do you mark ride hight with the wheel off, seems like with the wheel off it would be hard to know exactly where 0 is. Is it a guess, do you measure from the body? And we know that from 0, full up and full down is not a useable range. How much travel are you allowing for up and down before you quit trying to solve a bump steer condition.

1 and 1/2 inch above and below ride height is a reasonable range to address bump steer. With my shocks and springs I dont use more travel than this even when crashing over the curbs. Not sure how the stock setup will behave, but if you have addressed the change in that range i think you are going to be fine anyway.

I also wonder if I need to get some corner scales, have you set corner weights yet. I think I need to do this first. These are kind of spendy thoough.

Yes scales are expensive. Before I had them I simply set the car up so it was level with me in the car measuring at the 4 corners of the frame in front and behind the wheels. If you can add a little rake to the car (front of the frame a little lower then the rear) that will help you, but its not critical. Just make sure the car is level side to side with you in it.
When I got the scales just recently I measured the corner weights and I was close enough with this method to not cause issues on the track.

If I were you I would get the bump steer gauge before the scales. I think you have far better investments to make in the setup before you buy scales. Those are the type of thing you can check once and be all set. Any NASA event has scales that I am sure they would let you use to setup the car. you can roll on take a measurement then adjust your spring perches roll on again and you will be plenty close enough for the street. Consider the fact that a passenger massively changes the corner weights of your car and on the street you just dont notice it. Even on the track, unless you are driving at the limit, it does not matter.

If your toe settings are way off you will feel those on the street. I have really screwed mine up when I got things misaligned rushing at the track and its just the car will turn better left than right....not like your car is going to suddenly spin off the road and crash you into the woods.

hope that helps.

kabacj

04-03-2015, 09:33 AM

Hey Gene,
I have an inexpensive bump steer gauge I got from speedway motors,It works good I Was able to get the front bump steer very close to zero about .005" in 3" of travel .Here is a link to the instructionshttp://static.speedwaymotors.com/pdf/910-82700.pdf . Since you have to unload the springs to set the bump steer the scales and corner weight get done after your alignment and ride height is set.

John,

I've been replacing my upper control arm and playing with the alignment but before I finalize the alignment I am going to check and set the rear bump steer. It is recommended to set your bump steer so that it toes out if you can't eliminate it. Bump steer kits for c5 corvettes cost about $200.00 the front kit should work on the rear.

Hi Mike,

Factory Five tell me that we want 1/16 of total toe in per inch of compression travel in the rear and 1/32 of total toe out in per inch of compression in the front.

Agree with you a cheap bump steer setup is the way to go.

fastthings

04-03-2015, 11:10 AM

Thanks guys

kabacj

04-07-2015, 05:40 AM

Over this weekend I took literally hundreds of measurements of the rear suspension motion.

My goal was to map out how adjusting the toe links using shims changes the behavior of the whole suspension.

I use a bump steer kit that replaces the corvette toe link.

This is a photo from last year but it shows the part.
http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/8FB4896E-E095-4C70-9EA3-D60BD1D4064F-10047-000014F912D3D436.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/8FB4896E-E095-4C70-9EA3-D60BD1D4064F-10047-000014F912D3D436.jpg.html)

The key is the longer stud that fits into the tapered hole in the C5 upright. This allows adjustment of the rate of toe change. Not a big deal to worry about at highway speeds. If you are going 130+ you have one wheel turning in at a higher rate than the other you might have what some people falsely claim is aero instability. It's just your rear tires steering the car as the suspension travels up and down. I can see how people make the mistake. People that race the corvette do this same mod. A stock corvette is far less stiff than a GTM so the compliance of that setup may mask setup flaws.

The VIR high speed back strait has some bumps and dips that cycle the suspension through its travel. I noticed the car would shimmy from the rear end over these sections. Adding damping to the rear shocks lessened the shimmy. Hmm.

Now that I have mapped the rear suspension travel on my car with literally over 200 measurements and seen a thin .027 inch shim change the toe rate. Im reasonably sure that people who don't set their bump steer will not have equal rates per rear wheel.

Another trick i found was adding rollers under the bottle jack allowed for more accurate measurement. The rollers eliminate any binding introduced by the suspension Traveling in an arc connected to a static bottle jack.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/E3A78D42-10F8-451E-A263-E0A5354FF524_zpsanpozato.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/E3A78D42-10F8-451E-A263-E0A5354FF524_zpsanpozato.jpg.html)

Fraser D

04-07-2015, 07:07 AM

kabacj

04-07-2015, 08:09 PM

John,
Great information!
I have experienced the rear become unstable when transferring the weight forward quickly at speeds 130+ or when the road gets a little lumpy. It is less noticeable when I roll off the throttle and feed in the brake.
Your thread is a huge help to me in making sure that I make the right upgrades and know how to measure changes for this great car. I have to say that out of the box, if set up correctly the GTM handles very well up to that point, but I don’t know many production cars that can easily exceed 130mph on a track.

Glad you find the info helpful Dave. Since we are starting from a box of parts it's reasonable that we need to make the proper adjustments to get super car performance.

I got a few pics from my track day at VIR.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/C48D4E35-5626-4294-A7E7-84AD38701556_zpsyocd93hi.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/C48D4E35-5626-4294-A7E7-84AD38701556_zpsyocd93hi.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/C17C8E70-B073-4B6E-B2D3-1F21C9863293_zps7v7zlbqr.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/C17C8E70-B073-4B6E-B2D3-1F21C9863293_zps7v7zlbqr.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/F0368EB8-6172-4DD4-863D-E15440B71582_zpsea8o40xk.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/F0368EB8-6172-4DD4-863D-E15440B71582_zpsea8o40xk.jpg.html)

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/0015EE5E-00E0-4BE0-AE9D-9CC7B1A7CBB6_zpssz6vr6do.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/0015EE5E-00E0-4BE0-AE9D-9CC7B1A7CBB6_zpssz6vr6do.jpg.html)

Kempo

04-07-2015, 08:40 PM

Great info John. The car looks so COOL on those pictures!!!!

OZIGTM

04-07-2015, 08:47 PM

John,
When you were putting the rear end through it's movements did you notice if the amount of anti-squat makes any difference with instability?
I know Crash said they have reduced the amount of anti-squat in the GTM-R.
Cheers,

Rohan

kabacj

04-07-2015, 09:05 PM

Great info John. The car looks so COOL on those pictures!!!!

Thanks Hugo!

John,
When you were putting the rear end through it's movements did you notice if the amount of anti-squat makes any difference with instability?
I know Crash said they have reduced the amount of anti-squat in the GTM-R.
Cheers,

Rohan

Hi Rohan

I have not gotten to the point where i can adjust anti squat. The way I figure it I first need to optimize the Factory five design before I change it.
I think the key point to take away from this step in the process is that your bump steer or roll steer will not be the same unless you actually measure and set it. I made the mistake of assuming that if I set both sides with the same number of shims my bump steer would be equal. Not many alignment shops are even going to check this setting. Maybe a race shop would but that will cost you some labor.

In fact I needed to make thinner shims to actually match the rates from side to side.

While i think my measurements are a bit of overkill because I am measuring 1,000ths of an inch. I firmly believe that your calculations are only as good as your least accurate measurment.

Once I test out this batch of changes on the track I'll see if anti squat is a concern for me.

I'm far from an expert, but i have a feeling that once you dial in the basics of proper toe, camber and bump steer for the GTM. The next round of changes are more about what you like as a driver. Like I said I'm not sure of that, but you can be sure I will report what I find. :).

johngeorge

04-08-2015, 06:30 AM

John, put some stripes on that thing! plastidip! :)

kabacj

04-08-2015, 05:46 PM

John, put some stripes on that thing! plastidip! :)

100% right John. I need to do the plasti dip thing while I finish the body mods. I just need a little warmer temps to get that done. I'm up north by you today and it's sleeting! It's the winter that never ends.

flickery8

04-09-2015, 08:26 PM

Damn, that sucks, glad you didn't tear it up. I remember a thread about a guy trying to get the willwood adjuster to adjust enough to the back. I went out and took mine apart, it did seem that the master on the left, I think, always got more preasure. It just so happens I have the front using the left master. I have not tested mine yet, I hope I can dial up too much rear bias.

Have you been able to get your brakes to lock up front or rear, lock to lock, with your adjuster? I wonder if you will be dialing in a little more rear bias, because of that. I love it that you share the bad with the good. Ken Block would have grabed his E-brake.:)

John,
The first year I drove my car on the track I won a TOYO hat for going off track more than anyone else. Some of this is inexperience. However, for those reading your great story here, my problem was trail braking. Any braking with wheel turned resulted in me going the wrong way down the track (I still have grass and hay everywhere). I do think I have to much rear bias as the front pads look new when replacing the rear. Do you find your car to be hyper sensitive to wanting to come around with any trail brake? This could even apply to agressive street driving where you have posts and curbs instead of soy beans like we have here.

kabacj

04-10-2015, 05:01 AM

John,
The first year I drove my car on the track I won a TOYO hat for going off track more than anyone else. Some of this is inexperience. However, for those reading your great story here, my problem was trail braking. Any braking with wheel turned resulted in me going the wrong way down the track (I still have grass and hay everywhere). I do think I have to much rear bias as the front pads look new when replacing the rear. Do you find your car to be hyper sensitive to wanting to come around with any trail brake? This could even apply to agressive street driving where you have posts and curbs instead of soy beans like we have here.

Hey fickery

Yes sounds to me like you have too much rear bias. I have found that trail braking actually is a benefit to transfer weight forward and aid front grip mid corner.

You should be replacing rear pads half as often as you change fronts. Definitely not more often.

It's possible to get lots of braking done with the rear only as you have shown, but as you also have experienced when heavy rear bias will hurt your directional control when trail braking. The big tires out back and the amount of slip in your differential will determine how much your car pushes or slides the front tires mid corner.

If you lock the rear tires mid corner, yep then you are going backwards. I personally like when the front tires lock first as that is the easiest to control and allows me the highest mid corner speed. Rear lock up in the rain is even worse.

I would screw the rod that goes from the rear master cylinder all the way into the brake pedal assembly. Try that. On the street in a safe place. We don't want to find out you only have rear brakes and the fronts have a problem.
Then start screwing the rod on the front master cylinder out of the assembly both things moving the brake bias forward. Once you have max stopping force then the fronts locking you are at a good starting point to fine tune the setup.

I put a square of duct tape on each rod attaching it to the balance bar on the pedal assembly just to be sure the rods don't vibrate in or out into a new adjustment.

Oh just remembered that you did need to trim one of the rods on the master cylinders as part of the build. Maybe you missed that step? I don't have the build manual handy. Maybe that has something to do with the imbalance. If somebody can check which rod is trimmed that would help.

John

eseethal

04-12-2015, 02:15 AM

Sorry to disagree, I think this is a misunderstanding of the balance bar concept.
See the Wilwood instructions (http://www.wilwood.com/TechTip/TechPedalTip.aspx).
The bias is only adjusted with the balance bar and not with the rods to the master cylinders. The rods only are adjusted to compensate for the different travel of the MCs. If the balance bar itself does not give you enough adjustment, switching to different master cylinders is the way to go.

Hey fickery
I would screw the rod that goes from the rear master cylinder all the way into the brake pedal assembly. Try that. On the street in a safe place. We don't want to find out you only have rear brakes and the fronts have a problem.
Then start screwing the rod on the front master cylinder out of the assembly both things moving the brake bias forward. Once you have max stopping force then the fronts locking you are at a good starting point to fine tune the setup.
John

kabacj

04-13-2015, 05:03 AM

Sorry to disagree, I think this is a misunderstanding of the balance bar concept.
See the Wilwood instructions (http://www.wilwood.com/TechTip/TechPedalTip.aspx).
The bias is only adjusted with the balance bar and not with the rods to the master cylinders. The rods only are adjusted to compensate for the different travel of the MCs. If the balance bar itself does not give you enough adjustment, switching to different master cylinders is the way to go.

Hi Eseethal.

I don't disagree with you. In this case however the assumption is that the current bore master cylinders work with the calipers in use. I have not heard of anyone unable to adjust bias so it is balanced front to rear.

If bias is way off my guess was that the rods were not adjusted properly. I need to dig out my manual. I'm pretty sure one rod needed trimming. If that step was missed. Maybe its impossible to get proper balance using the bar alone.

My other guess is that the front master cylinder is damaged . I had a torn seal in my clutch master cylinder that could have been damaged during installation.

One way or another something is wrong.

Thanks for the clairification.

John

crash

04-13-2015, 10:29 AM

kabacj

04-13-2015, 05:01 PM

Just for the record, we changed our MC sizes on one of the MCs. I can't remember which one and to what size, but when we went to C5 front calipers all the way around I'm pretty sure that is when we changed the master cylinder sizes. The car really works better with larger rear brakes. We have since gone to a larger StopTech front caliper, but only because we wanted a larger pad to get more pad life out of the brakes for the 25 hour race. The C5 fronts all the way around is a pretty good, and economical, setup.

I also use the stop tech 6 pot up front and ended up using their 4 pot out back. Stop tech engineers agree that the GTM can use more brake than the c5 stock setup.

Last time at the track my brakes were great! I was side lined by a hole in my upper cv boot.

I imagine it was hit by a sharp rock during my Saturday race. It's kind of weird to see a hole like this. The hole was invisible unless i deformed the boot. I wrongly assumed that grease was leaking out from the band clamp or metal to metal joints. I cleaned up the mess re clamped and l cleaned and made fresh RTV gaskets. Only to respray the engine with grease

Here was the culprit.

Invisible unless I dimple the rubber.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/B09F7F21-5FE8-417F-B401-9E0933FFA14D_zpskdj5gsqa.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/B09F7F21-5FE8-417F-B401-9E0933FFA14D_zpskdj5gsqa.jpg.html)

eseethal

04-14-2015, 01:34 AM

John,
yes, I had to change my rear MC to a smaller one to get more rear brake bias with my Z06 big brakes. The balance bar is only for fine tuning the bias. And the length of the rods do not change the brake bias in any way, unless the adjustment it totally off. It only affects the balance bar position, with a moderate pedal effort the balance bar should be straight.
Compared to a Corvette the GTM has way more percentage weight in the rear so it normally needs more rear brake.

@flickery8: Having to much rear brake is indeed a little strange. Look for trapped air or a defective MC. You could easily measue brake temps with a infrared temp gauge. If the front disks are colder than the rear ones you will know there is less performance with the front brakes.

mikespms

04-14-2015, 08:09 AM

Hey John,

Here is my 2 cents,I used the corvette abs and don't have a bias problem but in the process of researching the compatibility of the master cyls with the ebcm and adjustment of the balance bar I spent some time on the phone with wilwood tech service and got conflicting info from tech and finally they put me in contact with the engineer that developed their corvette brakes and according to him the 6 piston and 4 piston rear combo should use a 7/8" bore master for proper volume but that increases the pedal effort since we are not using a power buster,by using a 3/4" master the pressure will increase,the volume will decrease giving you a better pedal feel.Wilwood recommends a 3/4" master for their corvette system and you can use a 5/8"master to increase the pressure to lessen the pedal effort with the wilwood brakes but they don't recommend the 5/8"master with the corvette brakes because the lack of volume if you are using the corvette abs. That been said you could use a 3/4" and 5/8" master to adjust you bias but it was not recommended with the corvette brakes. As far as bias on the pedals assy it is done with the balance bar and it is what it is,you need to make sure that you have free play on your master cyl rods or your will be dragging you brakes.An adjustable valve is an option. On the clutch side you need to cut the rod or you will bend it, I change form the FF supplied 3/4" master to a 5/8" master for a better pedal feel and slave operation.

Mike

crash

04-14-2015, 09:49 AM

Also note that pad material will make a HUGE difference, so if you are having an issue where the rears are locking up first and the pad material is different front to rear, the first thing I would do is make sure and change to the same material at both ends. This can have a dramatic effect on how the brakes operate.

kabacj

04-16-2015, 05:11 PM

Hey John,

Here is my 2 cents,I used the corvette abs and don't have a bias problem but in the process of researching the compatibility of the master cyls with the ebcm and adjustment of the balance bar I spent some time on the phone with wilwood tech service....That been said you could use a 3/4" and 5/8" master to adjust you bias but it was not recommended with the corvette brakes. As far as bias on the pedals assy it is done with the balance bar and it is what it is,you need to make sure that you have free play on your master cyl rods or your will be dragging you brakes.An adjustable valve is an option. On the clutch side you need to cut the rod or you will bend it, I change form the FF supplied 3/4" master to a 5/8" master for a better pedal feel and slave operation.

Mike

On the brake caliper vs piston setup.

Stoptech custom sized the pistons in the calipers they sent to match the willwood master cylinders and pedal assembly that comes with the kit. I must say I am happy with it and the balance bar is all I need in order to adjust bias. I am sure you cant get to the same place by adjusting the master cylinders to the calipers you ended up using.

Thanks for the info on the clutch MC. I knew I remembered cutting something

Also note that pad material will make a HUGE difference, so if you are having an issue where the rears are locking up first and the pad material is different front to rear, the first thing I would do is make sure and change to the same material at both ends. This can have a dramatic effect on how the brakes operate.

Crash,

I ended up using the performance friction PFC 7793.01.18.44 in the fronts with matching compound rears. I like the bite and ability to modulate as well as the fact they last forever. Normally you get good wear or good bite, but I think the light car and 14 inch rotors helps get both.

crash

04-17-2015, 09:08 AM

John-

The PFC pads are something I have really encouraged our team (PDG) to try. According to my source at PFC they should have reasonable bite characteristics, and also last about 30% longer than any of the other manufacturers pads. Unfortunately, because of costs and the fact that we have a ton of stock on the shelf of other manufacturers pads, we haven't tried the PFCs yet. The other thinking is that we know how to use what we have, and the only time we have to change pads during a race is at the 25 hour event, where we change them at about 12 hours, so 30% better wear doesn't translate into not having to change the pads so we simply haven't spent the money to try the PFCs. Good to hear from you that they are performing as PFC advertises though.

johngeorge

04-17-2015, 03:13 PM

flickery8

04-21-2015, 09:51 PM

kabacj

04-22-2015, 05:02 AM

John,
Thanks for your feedback on trailbraking, I am looking into a few things. Your new wheels look great. What size tires and wheels are you running this year? Will you use a different compound on the front and rear again?
thanks

The wheels are OZ racing 18x10 and rear are 18x12 with 2011 zo6 offset. They fit well and allow me to run 345s in the rear and 285, 295 or 315 up front. So far I have tried 245 on the stock GTM rims as well as 275 and 285 on the 10 inch wide OZ rims. When I am satisfied with the front tires I will adjust the body to cover the tires.

I have four sets of front tires to test in the next few days I'll let you know what I find out.

So far this spring I am running 285 Hoosier A7 up front and Hoosier 245 R7 out back.

The A7 is the autocross compound so it heats up more quickly. Next week I will be at New Jersey Motorsports park for two days testing then heading down on Thursday to VIR again for the NASA Hyperfest. Since the chances of warmer weather are good I am bringing along a set of 295 R7 fronts. Just in case the autocross compound can't take a warmer track temp.

The GTM is really easy on front tires. That's why I trail brake to keep them hot.

A shot with a better look at the wheels.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/ACBC7361-4ADA-4117-BFFD-81702C67E9D5_zpshfyyqdeu.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/ACBC7361-4ADA-4117-BFFD-81702C67E9D5_zpshfyyqdeu.jpg.html)

John

crash

04-22-2015, 07:54 AM

Have you guys looked at the Pagid yellow enduro pad? We used them on ed's 25hr car and based on the wear we were getting we didn't have to change pads in the race. The calipers we were using allowed us to use a pad that was .8in thick, massive pads...

We did look at the pagid yellows. At the time, three years ago, the company was going through a transition of ownership or something and the pads were not available for our calipers. The other problem is that because we are using all the "stock" FFR suspension, which equals stock Vette suspension, we are not able to fit the calipers that allow really thick rotors and pads. I have a nice set of Alcon calipers that use a 1.25" thick rotor and the pads can be 28mm thick, but there is no way to make these work with a stock Vette upright because the distance between the rim and the rotor simply can not be made large enough, so we are restricted to 18mm thick pads.

kabacj

04-24-2015, 05:04 AM

After all this discussion about brakes and brake balance and how much the rods that drive the master cylinder contribute to the brake balance as well as how much adjustment one can get with the balance bar it was clear to me we needed some data.

I especially wanted to measure the range of my setup. I wanted to be able to take it all apart put it back together and exactly duplicate the adjustments then verify them. I did some research. Turns out there is equipment for just such a purpose.

I got this nice setup. It has the adapter for my calipers and quite a few others.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/7113720A-394F-4C09-B29A-4BECD7F97671_zps5ihv6i9b.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/7113720A-394F-4C09-B29A-4BECD7F97671_zps5ihv6i9b.jpg.html)

I quickly instaled the gauge. I had a helper note down the pressure while I repeatedly tried to simulate max braking I do on the track. The test went well. I was able to repeatedly get the same pressure.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/A1AD6739-A7B7-4470-B802-0CBC2DBF448B_zpsmom1ddhc.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/A1AD6739-A7B7-4470-B802-0CBC2DBF448B_zpsmom1ddhc.jpg.html)

That was good since I need to measure one wheel at a time, duplicating the pedal pressure is key to a good data set for all 4 corners.

It was getting late so tomorrow I will measure each corner to get a baseline. Then I'll start tweaking the adjustments to see what kind of range I have.

johngeorge

04-24-2015, 08:02 AM

man I cannot believe you dont datalog front and rear pressures! just sayin I do :)

crash

04-24-2015, 09:27 AM

We do as well. One of the guys on the team owns a company that is getting ready to release a product that will turn your tach into a brake bias gage. We have been testing it for the past 3 years and it works very well. We do notice slight variations, which are attributed to the fact that we are running the cheaper master cylinders, but it works REALLY WELL. The sensor can also be used to data log brake pressures and tells you the maximum pressure that the system saw since last being reset on the tach as well. So while the data logging function is there, many will just use the tach feature to get the info they need. Look for it shortly from Tel Tac.

EDIT: I talked to the company owner about the product and asked why it was not released yet and he said that it is because they are finalizing a smart phone user interface, so you may not need a stand alone data system to record readings, I don't really know. Maybe he was just talking for setup. Anyway, the phones are amazing tools, and I can't wait to see the finished product that we helped develop with the FFR PDG GTM.

kabacj

04-24-2015, 02:36 PM

We do as well.

man I cannot believe you dont datalog front and rear pressures! just sayin I do :)

Oh now everybody has brake pressure telemetry:)

But I agree I do need to add it. My current setup is CAN based so I need to add a few sensors.

It's on the list.
John

kabacj

05-04-2015, 05:30 AM

3 tracks in 6 days

I was lucky enough to get lots of track time this week.

I visited New Jersey Motorsports park lighting and thunderbolt then drove down to Virginia International Raceway.

Lots of testing and some very good information.

I am 100% sure that anyone who reports their GTM is unstable above 150 never set their rear bump steer.

It's not something an alignment shop will normally do but it's critical on a GTM. The super stiff chassis will translate any misalignment and it's very noticeable above 150.

With the bump steer set, I was able to remove most of my rear toe in with only 1/8 total toe in.

If you plan on tracking or doing 1 mile events with your GTM you must set the rear bump steer.

Check out all the Factory Five cars at VIR! By Saturday AM we had 7 factory five cars in our pit area.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/3F74BA99-F8F7-488B-90E5-41012E5385C5_zpskcc45lfd.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/3F74BA99-F8F7-488B-90E5-41012E5385C5_zpskcc45lfd.jpg.html)

Hyper Fest was great. We took a helicopter ride after the race on Saturday.

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/6518E3A2-92FE-4BF6-89D2-86B4500AB0B1_zps3aksq8vy.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/6518E3A2-92FE-4BF6-89D2-86B4500AB0B1_zps3aksq8vy.jpg.html)
I can see my car from here!

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/67EF95EA-166B-4E7B-834F-91447D550D44_zpsfvhpj5uo.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/67EF95EA-166B-4E7B-834F-91447D550D44_zpsfvhpj5uo.jpg.html)

John

fastthings

05-04-2015, 07:12 AM

mikespms

05-04-2015, 08:02 AM

kabacj

05-04-2015, 09:13 AM

Good news on your setup, thanks for sharing. I knew the rear bump steer was huge, I don't know why the guys on the Corvette forum don't seem to be able to figure it out. For years you can find thread posts of them doing strange things from the rear suspension.

Hi Gene,

I agree with you, I think the internet has quite a few stories about people who chase the wrong things to setup the corvette suspension.

C5 and C6 corvette racers definately know the story. The corvette suspension is just too compliant for track use.

Soft rubber bushings that get worn out lead to most of the problems on the street. A suspension that changes adjustments becuse of the soft bushings is always a bad thing. The car was setup out of the factory to be cushy and smooth.

On the GTM with a super stiff chassis and lots of traction with sticky tires its even more magnified.

The hard parts from the C5 are very good, they just need to be rebuilt and or upgraded then well adjusted after you put them in the GTM.

Fraser D

05-04-2015, 03:22 PM

John,

Great info on the rear toe link issues. I am in the process of implementing Mike's front control arm upgrade but the rear link upgrade is next on the long list of suspension upgrades.

fastthings

05-04-2015, 04:49 PM

You got the life of a rock star, cool fun.

kabacj

05-04-2015, 04:59 PM

Hey John,

Sounds like great time, do you have any track time video? Are you using the corvette toe links in the rear and if so did you use a corvette bump steer kit? How about your dry sump system did you get it dialed in and how is the sequential trans working?

Hey Mike I was lucky enough to get some views from outside my car this week. So yes I will post some video. The dry sump pressure is much lower now at 45 psi idle and 70 psi at redline. ARE were very helpful and the fix was simply clipping a few coils off a detent spring.

I did upgrade the rear toe Links and added a rear bump steer kit.

This is an old picture but it shows the toe links

http://i1073.photobucket.com/albums/w389/kabacj/Factory%20Five%20GTM%20roll%20cage%20modifications/F09D7366-3342-4B3B-9A2B-AD9AFF5A32A2_zpssf3o8n8p.jpg (http://s1073.photobucket.com/user/kabacj/media/Factory%20Five%20GTM%20roll%20cage%20modifications/F09D7366-3342-4B3B-9A2B-AD9AFF5A32A2_zpssf3o8n8p.jpg.html)

The transmission has been working great but I think I might have worn out the third gear engagement fingers or dog rings.

I'm going to pull the transmission to check it out this weekend.

kabacj

05-05-2015, 04:47 AM

You got the life of a rock star, cool fun.

Ha ha. I wish. The rock stars show up with tractor trailers and a pit crew. We had a bunch of them this weekend. Im the driver, mechanic and pit crew. Not very glamorous, but doing it all yourself has its own rewards.

crash

05-05-2015, 08:18 AM

I know you said it's an old picture, but you did put the lower sway bar mounting nut back on, right?

Also, I would be VERY surprised if you have worn out any dogs on your Mendeola transaxle. We abuse the heck out of our gear boxes for dozens and dozens of hours and have done that for YEARS now. In all that time we have experienced ONE dog failure and it was during this last years 25 hour event. It was a major failure of the entire slider, but the transmission just kept going. It was truly amazing.

When we first tested the Mendeola sequential dog box, we essentially had a free demo box to try out. Myself and another driver were tasked with driving it as hard as we possible could for about 8 hours of drive time to see if we could break it. I shifted with no clutch, ground the dogs MANY times, missed gears, etc. etc. and then we opened up the box to see nothing but a few chips out of the faces of some of the dogs. I have never been so brutal on a gear box and seen such little damage. The Mendeola's are STRONG.

In any event, I don't know how your bodywork clearance is, but for us, we can pull the box apart with it still in the car. This may be easier for you or it might not, but the tear down of the transaxle is very simple, especially if you are just pulling the stack out to check things out. Ian should be able to walk you through the roughly 5 steps to pull the gear box down.

What is much more important for us, and the gear boxes are pretty particular with this, is the adjustment of the shifter stops. If you get this wrong or if they get a little out of adjustment then the gear selections will not happen smoothly and sometimes the box will pop back down to the previous gear because it wasn't fully engaged in the next gear. I cannot stress this enough. If you haven't already, pay particular attention to your shifter stop adjustment.

kabacj

05-05-2015, 11:02 AM

What is much more important for us, and the gear boxes are pretty particular with this, is the adjustment of the shifter stops. If you get this wrong or if they get a little out of adjustment then the gear selections will not happen smoothly and sometimes the box will pop back down to the previous gear because it wasn't fully engaged in the next gear. I cannot stress this enough. If you haven't already, pay particular attention to your shifter stop adjustment.
Hi Crash,

HA HA yes, I did put the sway bar nut on.

Your comments about the shifter adjustment are very interesting. Ian actually mentioned that he would call you as he thought you had experience with this.
My hunch was that its an adjustment thing, but I was focusing on the cable throw and cable free play and the position of the cable attachment on the flag that the cable attaches to on the transaxle itself. When none of the adjustments I made fixed it I figured id check out the internals.

I tried many many combos over the past 5 days and none were able to resolve the issue I have in third gear. I did not however adjust the shifter stops… come to think about it. I only had this issue after one of the shifter stops backed out and actually prevented me from shifting up a gear.. that was scary ! This all happened back in March. I thought I really broke something that time.. only after I was in the pit did I see that the adjuster had backed out. I tightened the stops and it shifted again , but it was not the same.... but maybe it was the adjustment I had made to the shifter stop that was the cause of the whole thing! I did not make the connection.

I must have been lucky with my first shifter setup and install because it just worked flawlessly without adjustment.

If you are right that would be AWESOME! Luckily I can make it happen on the street under 50 mph so I can just test it around my neighborhood. I love the transaxle. I am reasonably gentle on it most times and the oil never shows any significant metal.. It did not make sense that there was a failure however I did not know what to check next.

Thanks a lot for the tip .

crash

05-05-2015, 11:49 AM

If you are running a cable shifter I would bet that it is an adjustment issue. This is one of the specific reasons that we DON'T run a cable shifter. They tend to go out of tune with cable stretch. The other reason is so that we can feel things transmitted through the solid shafting better.

With using a cable shifter I would be highly tempted to put the shifter stops on the flag at the gear box. In this way it wouldn't matter where the actual hand held shift lever ended up, the flag would move to where it was supposed to be and no further. This would have more wear on the cables, but it would eliminate the issue of the shifter stops going out of adjustment.

kabacj

05-05-2015, 02:13 PM

K
If you are running a cable shifter I would bet that it is an adjustment issue.

Again Crash,

Your experience is most helpful.

I understand the rod shift solution as that would make for both a more positive shift and as you say it’s not going to change. Especially important for 25 hours of driving without adjustment. And it also explains why in my experience hot cables shift slightly differently than cold cables.

I think I would go with the rod solution like you have before I did the stops at the flag, but we will see.

As long as I understand what the adjustment does and how my adjustment changes the behavior of the transaxle ill be fine. Until now I had no idea why my adjustments were not fixing the problem.

As I think about all the adjustments I made, I realize based on what you have said that none of them worked because none of them actually changed anything that mattered regarding this problem. The shifter stops were always allowing full travel of the flag at the transaxle. I actually made a point to make sure I got all of the throw available. Sounds like that’s exactly NOT what I should have done. HA HA I have proven you can NOT fix this issue by maximizing the flag motion.

Sure will be nice if all I need to do in order to fix this is turn an Allen head bolt to adjust the stops for the shift leaver throw.

crash

05-05-2015, 02:43 PM

If you go with the rod solution make sure you use aircraft U joints. Again, there is a huge difference in performance and the ability to stay in tune over long periods of time. I used 3/4" 4130 rods and I think PDG uses 1/2 or 3/4 solid aluminum rods. Try to avoid any bends in the rods. This was much easier for us because the center steer driver placement means that the shifter is almost right in line with the flag on the transaxle.

kabacj

05-05-2015, 08:41 PM

Here is a quick video from my telemetry. Notice how the Go Pro loosened up. That is what happens when you mess with the camera while you are sitting in the car waiting for the session to start.

Hopefully Jim in the blue and yellow challenge car in front of me got some good go pro footage. Also you can see how I was struggling with the shifting. I would just keep banging away till the shift indicator said the right gear. Definitely used up some of my attention, but I was still able to put down a decent qualifying time.

https://www.youtube.com/watch?v=-WowIqaOf4U&feature=youtu.be

johngeorge

05-06-2015, 06:22 AM

wow! very cool John. Ill look at Jim's quali video tonight, but only have the front camera as the rear I forgot to get from David the Koni guy.

Martin

05-06-2015, 08:24 AM

Is that Jim Schenk in the Blue/Yellow FFR? Wonder if he feels a little weird being chased by a guy in a car that he designed :)

Martin

crash

05-06-2015, 08:28 AM

After watching that I am just about 100% sure this is an adjustment problem. Notice how the issue is only on down shifts? If this was a dog problem you would have an issue where the transaxle would pop out of gear when you went from acceleration to deceleration. This is not happening. What is happening is that you are simply not getting enough throw on the shift mechanism. The bad part about this now is that you may have had this happen enough that the shift forks are now pushed out of alignment and the stack may need a tune up. This is something that is particular to the sequential because on the H pattern boxes it really doesn't matter because you can just move the shifter further to compensate for fork misalignment. Unfortunately, because the fork is moved with a precision drum in a sequential style box, once that gets out of tune the only way is to open the box up and make the adjustments. I would highly recommend that if you try adjusting the stops on your shifter and this issue is not resolved, that you send the box back to Mendeola for a tune up.

There is really only one thing that you can do to these boxes that will cause them grief and that is to not get the sliders fully engaged before you try and apply throttle. This tries to forcibly push the dog rings apart while the fork and drum system is still trying to push them together. This can cause problems with bent forks, or forks that become out of tune to the shifting drum.

Didn't look like you were on slicks? If you were they were pretty forgiving.

kabacj

05-06-2015, 08:55 AM

Is that Jim Schenk in the Blue/Yellow FFR? Wonder if he feels a little weird being chased by a guy in a car that he designed :)

Martin

I think he is happy. He has been a great help getting the car setup.

It's like watching your kids grow up.

kabacj

05-06-2015, 10:06 AM

After watching that I am just about 100% sure this is an adjustment problem. Notice how the issue is only on down shifts? If this was a dog problem you would have an issue where the transaxle would pop out of gear when you went from acceleration to deceleration. This is not happening. What is happening is that you are simply not getting enough throw on the shift mechanism.

Didn't look like you were on slicks? If you were they were pretty forgiving.

Hi Mike,

Well let me give you a bit more data to go on.

I was having issues on down shifts and yeah I agree that’s probably an adjustment thing.

What you might not have noticed in the vid is that I am shifting around any point when I am decelerating in 3rd gear. It puts me in the wrong gear for a few corners, but I just deal with then over slow down grab second, rev to the moon or I lug 4th.

Its not that the trans pops out of gear when I am in third, but its not fully in gear when im in third decelerating. I get lots of feedback through the shifter as the trans is almost in gear, but not. From what Ian was saying the dogs have ramps that will pull the gear into proper registration on acceleration under load I don’t get that benefit when decelerating. So I can grab third on an up shift from second but not grab and stay in third on a down shift from forth.

So it still might be an adjustment issue.. at least I hope it is.

Regarding the slicks I'm on them. Ha yeah im pretty busy in there even tho you don’t see it. During the down shifting I am fully clutch in so no deceleration from the motor I’m just braking then feathering in the clutch in to get the down shift to take when I see the right next gear indicated. Tricky so I don’t break the tires lose mid corner. Lots of fun 

crash

05-06-2015, 10:38 AM

Right, the dogs have ramps. The issue is if you do not engage enough to get to the ramp area then bad things happen. I think this is your problem. I would be highly surprised if you have damaged the dogs to the point that they no longer have a ramp and therefore will no longer hold the dogs together during accel/decel. And just to clarify, the dogs have ramps on both accel and decel sides. This is what keeps the slider engaged during both acceleration AND deceleration. Yes there is a time when neither ramp on either side of the dogs are engaged when transitioning from accel to decel, but unless there is a force trying to pull the slider out of position, no issues will be noticed.

Again, this sounds to me like an adjustment issue, but likely may not be one that can be addressed by just adjusting your shifter stops at this point. Without getting into the nuances of the Mendeola gear box, the shifter just "suggests" what gear the transaxle should be in and the internal drum and shifting mechanism then tries to ensure that the correct gear is engaged. There are really two things that can go wrong here.

1) The shifter cannot move the star wheel within the gearbox to the tip over point where the drum mechanism takes over and tries to put the slider into the proper gear, or

2) The shifter goes far enough to get the drum working properly, but because of an event that bent a fork or knocked the fork "out of tune" to the drum, even though the drum is doing what it is supposed to do, the fork is not moving the slider so that the dogs reach a tip over point where the pressure angle of the ramp takes over and holds the slider engaged.

Again, number 1 is easy enough to look at and try different adjustments. Number 2, however, requires some pretty significant work to correct. Note that number 1 can lead to number 2 in very short order. This is why it is CRITICALLY IMPORTANT that the shifter be set up properly as far as stops are concerned from the beginning. In the case of the Mendeola design, it is okay, and even preferable to adjust the stops so that the flag goes a bit past the star wheel tip over point. Not WAY past, but a little extra throw will not hurt anything. Again one of the problems is that cable stretch will reduce the amount of throw you see at the flag over time and can quickly lead to both problems number 1 and 2 listed above.