New 818 Configurations Windtunnel Tested

[Dave Smith]

We took the new 818 to A2 Windtunnel in Mooresville, NC to test the new nose configuration, nose insert design, and airflow/cooling variations of ducting.

The 818 program enters a new stage with the release of the newest configuration, the 818 Coupe. We’ve changed all the 818 models over to the new nose standard. All 818 models in production now and forward have this new nose design. The previous revision nose and headlight designs are still available for replacement parts or custom orders.


https://www.youtube.com/watch?v=0xOCYSTQx3E

Check out the wind tunnel work we’ve recently completed with the new design. The team is proud of the continuing evolution of the newest Factory Five. The 818C gives builders another way to make their 818 meet multiple needs. The car looks more aggressive, and is more aerodynamic than before.

We’ll have a new 818C and 818R at the 2015 SEMA Show next month in Las Vegas.

http://www.factoryfive.com/wp-content/uploads/2015/10/DSC_7666.jpg
We tested a tremendous number of variables over the day and a half of windtunnel testing.

http://www.factoryfive.com/wp-content/uploads/2015/10/DSC_7692.jpg
We tested the latest configuration of the nose insert for downforce, drag, and airflow/cooling.

http://www.factoryfive.com/wp-content/uploads/2015/10/DSC_7705.jpg
Every run generated a full set of data points.

http://www.factoryfive.com/wp-content/uploads/2015/10/DSC_7772.jpg
We removed the hard top and tested the 818 in S-trim (roadster).

http://www.factoryfive.com/wp-content/uploads/2015/10/DSC_7796.jpg

http://www.factoryfive.com/wp-content/uploads/2015/10/DSC_7813.jpg
We also tested the 818R with the new nose and the latest configuration nose insert with canards, front splitter, and aperture variations.

http://www.factoryfive.com/wp-content/uploads/2015/10/DSC_7858.jpg

[Dave Smith]

http://www.factoryfive.com/wp-content/uploads/2015/10/Wind-tunnel-frame.jpg
The outside of the windtunnel is almost as cool as the inside.

http://www.factoryfive.com/wp-content/uploads/2015/10/DSC_7682.jpg
818 designer Jim Schenck supervised all windtunnel testing.

[65 Cobra Dude]

Very cool Dave,

Henry

[David Hodgkins]

Looks great Dave! Will you be releasing the COD and downforce numbers?

:)

[Hindsight]

Thanks for the update. It appears the front grill has been updated vs what was shown at the open house. I really like the new grill and think it would look really good painted to match the body (sans the openings of course).

[Hindsight]

Also, do I spy a Spearco front mount air to air intercooler?!

[ben1272]

Wow. Never, and I mean never, does FFR cease to amaze me. The 818 is getting more and more functional and attractive as the days go by! Great work!

[Bob_n_Cincy]

Looks great Dave! Will you be releasing the COD and downforce numbers?
:)

Great job FFR.
I also would like to see the COD and down force numbers on the 3 configurations.
Most important to me is the numbers on the 818s original nose.
Thanks
Bob

[C.Plavan]

Also, do I spy a Spearco front mount air to air intercooler?!

Looks A2W to me. But we will see.
https://gspec.com/p-3971-intercooler-air-liquid-assy.aspx


BTW- I WISH I sat that low in my R.

[redfogo]

A front mount intercooler would lag a lot so I have my doubts. I love the new grill, it looks so much better with it!

[Flamshackle]

stoked to see this Dave,

well done again FFR cant wait to hear about the data.

[shinn497]

I swear the new nose is looking closer to Olmos's redesigns more and more. Which is interesting since I know him and FFR were in contact at one point.

[freds]

What air speed, or range of air speeds was/were used during the tests?

[Jim Schenck]

That front intercooler on the R is air to air. We used most of the summer testing different intercooler configurations in this car, two different air to water and 3 different air to air, and this is the latest from our test at Palmer a few weeks ago. That test was interrupted by an engine management issue so we are leaving the car this way for the next test as well. We did mostly aero testing on track at NHMS last month which also helped set us up for what we wanted to try in the tunnel as it gave us a chance to come back and build some new scoops and ducting to take with us.

The air speed during the smoke wand runs is around 45mph, no data is collected during those sessions they are just visual. The data logging runs are done with 85mph wind speed and then the software at the tunnel extrapolates to any speed you want from there.

[DMC7492]

Great to hear about the testing during the summer of the intercoolers!
The big question is what are the results?
I am particularly interested in the side vents in the rear, how did the tunnel testing prove their efficiency?

[Hindsight]

Thanks for the additional info Jim.

[Pearldrummer7]

That front intercooler on the R is air to air. We used most of the summer testing different intercooler configurations in this car, two different air to water and 3 different air to air, and this is the latest from our test at Palmer a few weeks ago. That test was interrupted by an engine management issue so we are leaving the car this way for the next test as well. We did mostly aero testing on track at NHMS last month which also helped set us up for what we wanted to try in the tunnel as it gave us a chance to come back and build some new scoops and ducting to take with us.

The air speed during the smoke wand runs is around 45mph, no data is collected during those sessions they are just visual. The data logging runs are done with 85mph wind speed and then the software at the tunnel extrapolates to any speed you want from there.

Definitely curious on your results with the different intercoolers, Jim!

[C.Plavan]

That front intercooler on the R is air to air. We used most of the summer testing different intercooler configurations in this car, two different air to water and 3 different air to air, and this is the latest from our test at Palmer a few weeks ago. That test was interrupted by an engine management issue so we are leaving the car this way for the next test as well. We did mostly aero testing on track at NHMS last month which also helped set us up for what we wanted to try in the tunnel as it gave us a chance to come back and build some new scoops and ducting to take with us.

The air speed during the smoke wand runs is around 45mph, no data is collected during those sessions they are just visual. The data logging runs are done with 85mph wind speed and then the software at the tunnel extrapolates to any speed you want from there.

I'm SOOOOOOOO happy you guys are actually testing things. We would love info on what you found out with the intercoolers.

PS can you throw a new front end on the truck to SEMA that I can pick up? I'll be there this year. Will the old canards work, or are there totally new ones for the new fenders?

[Jim Schenck]

My current thinking based on what we have seen testing intercoolers seems to be pointing to different solutions based on the intended use of the car. Testing the air to water systems on the track has shown that with no recovery time they tend to gradually increase in temps over the course of the longer runs, whereas on the street the recovery time at either cruising speeds or idle allows them to stay cooler than either the top mounts or relocated air-to air units still in the engine bay. The two W2W systems we tried were different in that one used a large reservoir and a medium sized cooler and exchanger and the later system used a bigger cooler and a full sized radiator as the heat exchanger with no reservoir. The second system worked better and was overall lighter than the one using the extra tank.

For air to air I still think the top mount is viable for stock and mild builds, on both street and race cars, and that is where we concentrated our street car efforts in the tunnel trying to find the best spots to pull and from and exit air to. The plan going forward for ducting to the top mounts is to use four inlets to feed the intercooler. The two side inlets are effective if they are cut out correctly (the cutout shape made a HUGE difference which was something we missed in our first trip to the tunnel) and either the decklid vents or the roof scoop ducts for the other two depending on which model it is.

During our track testing we also tried several different very large scoops feeding the intercooler from in between the humps and this was not as successful. Even with a large top mount (Turbo XS) the temps were not as low as we would like them to be and the drag/reduced downforce was not good at all. Airflow in that area is just very turbulent and the cockpit itself is a low pressure so air will actually flow backwards into it.

As far as air exit goes the best place is the lower section of the car, the upper vents still allow air to exit but the flow is much slower and more chaotic. The rear trunklid vent is somewhat variable, with the spoiler in place you get air flowing in, but with the wing in place there is not much flow through that vent at all. I still think the vent is useful, particularly for escaping heat when the car is sitting still, but it isn't a good place to get reliable air entry or exit from. Cutting additional vents on either side of the low vent seems to make the most sense for someone needing to get additional air out of the engine bay.

The front mount in the race car is really just going to come down to testing turbo lag. This setup will only be a real possibility for R models as the tubes run through the top of the doors, but the plumbing was actually pretty straightforward and the amount of tube relative to a WRX with a front mount is not that different (maybe 50% more but not 2 or 3 times as much). We stayed with a fairly small inlet tube to try and keep the overall volume down but we still have testing to do to see if this really is the best solution for big power track only cars.

Also on the R, the windscreen makes a big difference, improves drag, downforce, and cooling and running without it does not improve flow into the rear decklid area.

[Jim Schenck]

Chad,

Canards are different, the nose is pretty different in that area so we couldn't make the old ones fit. I might be able to fit some parts on the truck though, shoot me an email.

[Hindsight]

Great info Jim, very happy to see the testing continue and that you are sharing the info here.

[Bob_n_Cincy]

Thanks Jim,
Your comments were great at clearing up some of unknowns about airflow. I personally will reread your comments many times. Anything you can think to add later would be great.

Can you send out something to show us how to cut out the side intake ducts to get more cool air into the engine compartment?
Thanks Again
Bob

[Hindsight]

I'm guessing it's to ensure there is no lip on the inside edge of the scoop.....

[Jim Schenck]

The outer edge being a knife edge and the entire duct cut out so the air can't flow down to the bottom and out, the best thing we tested looked like this:

46425

[Jim Schenck]

Two other things we tried here were using a deeper duct and adding a lip to the outside edge of the duct. The deeper duct didn't work when trimmed the old way but because we figured out the trim later we didn't get to test it fully open and knife edged like the stock duct. Without that the duct was less effective, both with and without the lip, and not what I would expect but the stock duct was worse with just the lip in place but the cutout the same. This pic shows both the deep duct and the lip. We used this same exact lip on the other side but I didn't get a picture of that.

46426

[Sgt.Gator]

Double KUDOS for stepping up and taking on the airflow issues!!!!

I can't wait to see the aero drag / downforce numbers for the three versions of the car.

On the FMIC, that was something I was going to try. I run a Perrin FMIC on my LGT and see virtually no turbo lag. But as you already pointed out it's a race car so the engine is almost always above 4500 rpm. And if you enable flat foot shifting in the Cobb AP that helps too. Please provide details on your FMIC testing for the R folks!.

Thanks again, this is great stuff.

[Mechie3]

At 1:13 you can see the seam in the fender. Not sure about the center grill. It almost looks upside down compared to most implementations of that style of bumper.

[Frank818]

A lot of cool stuff happened here! It's great news.


The two side inlets are effective if they are cut out correctly (the cutout shape made a HUGE difference which was something we missed in our first trip to the tunnel).

Can someone define "cut out correctly"?


The outer edge being a knife edge and the entire duct cut out so the air can't flow down to the bottom and out, the best thing we tested looked like this:

46425

What is different here? The black trim or the cut out angle at the bottom of the vent?

[Jim Schenck]

The picture of the cutout on the driver's side of the car is what I am calling "correct" My comparison is to what we had for a cutout at the last tunnel test which is this:

46433

[Jim Schenck]

Also we tested I would call this style of trim incorrect (its a GTM but similiar shaped duct):

46434

[Scargo]

All great info! I'm glad I'm headed in the right direction. My side cutouts look just like yours! I'm hoping I can do AtA on mine with some fancy ducting.
http://thefactoryfiveforum.com/attachment.php?attachmentid=39148&d=1425050528

[Aero STI]

Great information. This is the most transparent thread I've seen from FFR regarding the 818 since I joined the forum.

[flynntuna]

The outer edge being a knife edge and the entire duct cut out so the air can't flow down to the bottom and out, the best thing we tested looked like this:

46425

Is that tape on the inside edge of the duct, and I'm assuming that is the inner fender I see looking in the duct?

[shinn497]

Wow I would love to see a guideline for duct cutting. Or maybe like a template you can place over the body?

[Bob_n_Cincy]

Wow I would love to see a guideline for duct cutting. Or maybe like a template you can place over the body?
Shinn
I marked up my picture to make a similar cutout.
Bob
46441

[Flamshackle]

wow great info thanks so much Jim.

So helpful for those of us yet to build.

[ehansen007]

Great work guys. Can't wait to see it at SEMA!

[Jim Schenck]

That is tape inside the duct, leftover from our airflow sensor being mounted there. The black you see inside the duct is the inner wheel well, just with truck bed liner sprayed on top of the aluminum.

[AZPete]

Jim, I've opened up the side vent and used a more open hex screen, but would you suggest a baffle or duct inside to direct air up towards the intercooler?

http://i210.photobucket.com/albums/bb180/AZPeteCobra/Side%20sail%20vent%202.jpg (http://s210.photobucket.com/user/AZPeteCobra/media/Side%20sail%20vent%202.jpg.html)

[freds]

Jim, I've opened up the side vent and used a more open hex screen, but would you suggest a baffle or duct inside to direct air up towards the intercooler?

http://i210.photobucket.com/albums/bb180/AZPeteCobra/Side%20sail%20vent%202.jpg (http://s210.photobucket.com/user/AZPeteCobra/media/Side%20sail%20vent%202.jpg.html)

I have difficulty imagining how air is going to go up to the inlet side of the intercooler from these ducts.
It seems that even if air does curl up towards the IC it will be heading for the downstream side of the IC.

Providing a current of cool air clearing out hot air from the engine compartment (a good thing anyway) would seem to be what they do.

Help me if I am not thinking straight.

My stock intercooler is functioning very satisfactorily with my isolation of the feed side from the engine compartment...I had also opened up the two "wheel well" air feeds. Great to see the wind tunnel smoke flowing into them.

See http://thefactoryfiveforum.com/showt...ighlight=freds


fred

[Jim Schenck]

Fred,

The airflow in all the inlets we tested was channeled into brake duct hose and routed to where the intercooler sits in the stock wrx top mount location. The airflow meters are provided by the wind tunnel and are hooked into their data collection system, they are 3 inch diameter which works well for some vents (like the decklid and roof scoop) but may be restrictive on the side vents. Since we were going for relative numbers I think this was ok, but for real world use I was thinking 4 inch duct hose would be better from the side vents. To be most effective the hose would need to be hooked into a box around the duct that allows it to collect the air and then channels it down. That is how ours was arranged into the 3 inch duct as well, albeit fairly crude and made mostly of duct tape.

I am also picturing a box that sits on top of the intercooler with 4 inlets, 2 three inch and 2 four inch, to force this channeled air through, but we haven't gotten that far yet and we still have to really process the data before we start making any new parts to try. We ran 39 separate tests so there is a lot to look through.

[AZPete]

Thanks, Jim!!
I epoxyed threaded studs around the vents a while ago so now, since you found the vents move air, I'll try making some ducts .

[Flamshackle]

Fred,

The airflow in all the inlets we tested was channeled into brake duct hose and routed to where the intercooler sits in the stock wrx top mount location. The airflow meters are provided by the wind tunnel and are hooked into their data collection system, they are 3 inch diameter which works well for some vents (like the decklid and roof scoop) but may be restrictive on the side vents. Since we were going for relative numbers I think this was ok, but for real world use I was thinking 4 inch duct hose would be better from the side vents. To be most effective the hose would need to be hooked into a box around the duct that allows it to collect the air and then channels it down. That is how ours was arranged into the 3 inch duct as well, albeit fairly crude and made mostly of duct tape.

I am also picturing a box that sits on top of the intercooler with 4 inlets, 2 three inch and 2 four inch, to force this channeled air through, but we haven't gotten that far yet and we still have to really process the data before we start making any new parts to try. We ran 39 separate tests so there is a lot to look through.

This information is gold! Will you guys be producing the external air collector box for sale?

[freds]

Fred,

The airflow in all the inlets we tested was channeled into brake duct hose and routed to where the intercooler sits in the stock wrx top mount location. The airflow meters are provided by the wind tunnel and are hooked into their data collection system, they are 3 inch diameter which works well for some vents (like the decklid and roof scoop) but may be restrictive on the side vents. Since we were going for relative numbers I think this was ok, but for real world use I was thinking 4 inch duct hose would be better from the side vents. To be most effective the hose would need to be hooked into a box around the duct that allows it to collect the air and then channels it down. That is how ours was arranged into the 3 inch duct as well, albeit fairly crude and made mostly of duct tape.

I am also picturing a box that sits on top of the intercooler with 4 inlets, 2 three inch and 2 four inch, to force this channeled air through, but we haven't gotten that far yet and we still have to really process the data before we start making any new parts to try. We ran 39 separate tests so there is a lot to look through.

Thank you Jim. Wish I were closer geographically...would love to spend time going through "stuff".

I am selling my #18 this weekend... decision driven by changed domestic circumstances. Its been fun.

fred

A question: Wouldn't it make the hose ducting simpler if you totally isolate the inlet side of the Intercooler as I have done. Creating a "plenum" so the hoses could feed into the plenum at any convenient place?

[TX-Lou]

This information is gold! Will you guys be producing the external air collector box for sale?

I would like to second that suggestion. If FFR can produce and sell an air collector box for the stock intercooler, plus maybe the inlet boxes that would be great. I'm sure I can put something together but it wouldn't look anywhere near as good and probably wouldn't work as well as something that was professionally produced.

[tmoretta]

I have re-purposed the stock WRX under hood mounted air collector box. I have also improved/sealed the FFR provided air collector channels from the two top scoops. Seems to be working fine. I may add larger scoops to sit on top of the hood openings.

[billjr212]

I have also improved/sealed the FFR provided air collector channels from the two top scoops. Seems to be working fine.

I did this as well, but I think I'm going to start from scratch and try to mock something up that is mounted (or bonded) directly to the engine cover itself.


I have re-purposed the stock WRX under hood mounted air collector box.

I like the idea of re-purposing the stock WRX under hood mounted air collector box. I may have to look into that as well (assuming I didn't sell it already). Would be nice to have everything mounted to the lid to allow easier access to the engine once the lid is opened.


I may add larger scoops to sit on top of the hood openings.

I considered this also, but with the soft top, it becomes a tight fit.


Look forward to seeing the FFR ducting solution if there is one. I won't be re-visiting this part of the project until the snow starts falling in Chicago.

[Jim Schenck]

We did try adding scoops (from the 65 coupe cowl) that roughly doubled the decklid duct opening, but placing them directly on top of that duct strangely they made the flow worse. We also tried cutting these ducts bigger but the frame gets pretty close if you go back very far and that compromises the shape, with that funky shaped but larger duct the flow was also worse than the stock duct. I am sure that there are things that will improve the flow in these areas but some of the more obvious solutions didn't act how we thought they would.

[Goldwing]

Jim, thanks for spending time on this topic. Would a NACA style inlet in front of the cutout help draw more of the airstream into the vent? Creating a low pressure area forward of the cutout to draw the airstream towards the opening, then positive pressure builds in the opening as the air stream rams into the opening. I add that last sentence to specify we aren't lowering pressure at the opening, rather forward of it, if I understand the principle correctly. Both inlet paths for the deck lid and side vents are straight lead ins and may not be pulling the airstream towards the vent opening, thus the airflow concerns.

I had been planning to isolate the vent air to the A2A intercooler using either both deck lid vents or the left side vent. I'd use the right side vent to feed intake air. Whatever I didn't use for intercooler air was to feed the engine bay in general. With the suggestion to feed 4 vents to the intercooler, will the engine bay at large have enough air to stay cool enough? I had thoughts to isolate the air leaving the intercooler to further behind the engine or to the center deck lid vent. It sounds like the former would be more effective from the testing you mentioned. Again, thanks for taking the time.

Rich

[Scargo]

Two 5" and two 4" diameter tubes would equal the 65 square inch area of my 2008 STi hood scoop. Though the side inlets might equal that area I would assume they cannot get the clean direct air the hood scoop does. Still, this is something to ponder. The box the tubes would feed into could have additional air fed from other places. Other scoops could be added. Side inlets could stick out more and increase in area. It could be a porcupine of scoops!
For my R, my current scheme is to only have a driver's side windshield and a covered passenger side, much like the Lotus 211. This might make the hump on the passenger side more useful as a scoop.

[Jim Schenck]

Rich,

The decklid duct has some of this effect from the recessed lead in, it isn't in the shape of a NACA duct and I am sure it isn't as efficient from a drag standpoint. I do agree there are ways out there to get more air into this duct, just a lot of testing involved to find what is the most effective. We did see a somewhat related effect on the roof duct on the 818C, when we taped over the windshield seam to smooth the air ahead of the roof scoop it cut down on airflow through the duct. Just having that little step slowed the air down enough to get more into the duct than without it.

For engine bay cooling there is definitely airflow under the car that can be tapped into, or what we did on the R is cut the front of the "pontoons" out right behind the front wheels. The thought was not only to get air to the engine bay but to help cool the radiator tubes going through this area as well. We just screened off the front to keep debris out from the front tire. I didn't try any tests on that area in the tunnel because the tires were not spinning, I didn't think the results would be meaningful in that particular area because of that.

Scargo,

We did run tests both in the tunnel and on track with no windscreen and just using the dash bump for the instrument cluster as an air diverter over the driver. Even with John saying the airflow around his helmet was smooth and not affecting him, the airflow in the cockpit area was still very turbulent in front of the hump on the passenger side. In the tunnel test both drag and downforce were considerably better with the full windscreen than without it, and in most every test we have done the area directly behind the cockpit has just been a tough place to get any clean airflow. In a lot of tests the air was flowing backward from the engine bay into the cockpit, we saw that with both the smoke at the tunnel and with strands of yarn at the track.

[DMC7492]

In a lot of tests the air was flowing backward from the engine bay into the cockpit, we saw that with both the smoke at the tunnel and with strands of yarn at the track.

Once again Jim thank you so much for sharing these test results. During the yarn testing was the complete car tuffted? Any pictures or video clips?

[bigAl]

Jim said ".... We did see a somewhat related effect on the roof duct on the 818C, when we taped over the windshield seam to smooth the air ahead of the roof scoop it cut down on airflow through the duct. Just having that little step slowed the air down enough to get more into the duct than without it."

Probably the windshield seam trips the boundary layer from laminar to turbulent, which has enough more energy to follow the form better.

[mindinclouds]

Probably the windshield seam trips the boundary layer from laminar to turbulent, which has enough more energy to follow the form better.

Exactly

Regarding using a plenum on the intercooler being feed by multiple sources.......
My day job is working with light aircraft..... Everything from exterior aerodynamics to designing flow paths for cooling air for air cooled engines and other accessories.

When converting dynamic airflow into static air pressure within a plenum, when the air is from multiple sources , you need to keep in mind that if any of the sources are from a location that would result in a different static pressure if used on their own, the end result could be simply adding an air supply source that would end up having reverse flow or at best, a flow much lower than would be possible if it was used on its own. I.E., all of the air sources have to have similar pressure capability or you will end up with flow moving between them instead of going through the intercooler. Unless you are willing to do pressure measurements at a lot of different locations (at speed), it is safest to stay with one source location, or at a maximum, two, with very similar physical characteristics (such as the scoop on each side). Even then, the way the two sources are connected to the plenum can have an adverse effect on how well it performs. Such as in the case where a lot of flex duct is being used. If there is a lot more (particularly if it has more bends) on one side than the other, one can have a negative interaction on the performance of the other (flex ducting has a lot of inherent flow resistance).

[Jim Schenck]

Exactly

Regarding using a plenum on the intercooler being feed by multiple sources.......
My day job is working with light aircraft..... Everything from exterior aerodynamics to designing flow paths for cooling air for air cooled engines and other accessories.

When converting dynamic airflow into static air pressure within a plenum, when the air is from multiple sources , you need to keep in mind that if any of the sources are from a location that would result in a different static pressure if used on their own, the end result could be simply adding an air supply source that would end up having reverse flow or at best, a flow much lower than would be possible if it was used on its own. I.E., all of the air sources have to have similar pressure capability or you will end up with flow moving between them instead of going through the intercooler. Unless you are willing to do pressure measurements at a lot of different locations (at speed), it is safest to stay with one source location, or at a maximum, two, with very similar physical characteristics (such as the scoop on each side). Even then, the way the two sources are connected to the plenum can have an adverse effect on how well it performs. Such as in the case where a lot of flex duct is being used. If there is a lot more (particularly if it has more bends) on one side than the other, one can have a negative interaction on the performance of the other (flex ducting has a lot of inherent flow resistance).

The flow reversal out addition ducts is something we have considered, and agreed best case would be if we could get enough flow from just one symmetrical pair of ducts. From what I have seen of the ducts we have I think we have ok airflow for a stock engine and intercooler using just two decklid vents but for either built engines or extended track use I think we need to have more flow than just one pair will provide. One way we may solve this is to separate the intercooler box into two separate plenums so each pair of vents feed their own area. The challenge here is that we would like this system to fit as many different configurations of intercoolers as possible, stock, STI, bolt in replacement, and oversize replacement, and there is a pretty big range of sizes among those. Also the rear decklid is fairly close to the top of the intercooler so that limits how we can pair the incoming vents as well. What I am picturing is a trim to fit composite box that also has an aluminum divider and likely one wall made from aluminum that can be slid in and out to fit the different size intercoolers. We are still early in the design stage though and I am sure we will be testing other configurations along with that before deciding on what direction we will go.

[Mad Dog]

Jim asked me to post this quick video of the 818R at the track.


https://www.youtube.com/watch?v=7X3lWS0opII

[Flamshackle]

The flow reversal out addition ducts is something we have considered, and agreed best case would be if we could get enough flow from just one symmetrical pair of ducts. From what I have seen of the ducts we have I think we have ok airflow for a stock engine and intercooler using just two decklid vents but for either built engines or extended track use I think we need to have more flow than just one pair will provide. One way we may solve this is to separate the intercooler box into two separate plenums so each pair of vents feed their own area. The challenge here is that we would like this system to fit as many different configurations of intercoolers as possible, stock, STI, bolt in replacement, and oversize replacement, and there is a pretty big range of sizes among those. Also the rear decklid is fairly close to the top of the intercooler so that limits how we can pair the incoming vents as well. What I am picturing is a trim to fit composite box that also has an aluminum divider and likely one wall made from aluminum that can be slid in and out to fit the different size intercoolers. We are still early in the design stage though and I am sure we will be testing other configurations along with that before deciding on what direction we will go.

Jim what about the coupe roof scoop? Are you confident that it will draw enough air to stand alone as a inter cooler feed?

[Scargo]

Jim, I suspected that you were trying for a production fix or something akin to "one size fits all". With our Rs I think that is unnecessary. Yes, there will be the person who does it by the book and perhaps, if there is an 818 class for racing, some mods might be illegal.
What I am getting to is that I am trying to think "outside the box" that you may be encumbered by. I wonder where else an STi intercooler (or two) might be located?
I'm not quite to that point yet and it's hard for me to visualize available space and how you would get air to it. I certainly don't see it staying, perched above a hot motor.

[apexanimal]

thoughts about pulling in a crap ton of air from the side windows that are a part of the hard top?

that's a typical move in mr cars and can provide a lot of air...

[Jim Schenck]

The scoop on the top pulls in a similar volume of air to the ducts on the decklid, however from that point it is a much easier path to the intercooler. My thought on the roof duct airflow is pretty much the same, good enough for stock engine, but big hp cars will need more than just that. Also the current ducts on the hardtop rear windows do flow a useful amount of air but that is also helpful in keeping the whole engine bay cool which was our intent for those. The windows themselves could be replaced with bigger ducts but they are a good help with reducing the blind spot, particularly on the passenger side, so keeping a decent size window in that area is still important.

What we are shooting for isn't a complete one size fits all, more of just a better baseline solution. There is still a place for water to air units on the street, and the front mount air to air in our R looks to be very promising for a road course only car, not to mention the rear relocated solutions that others have tried as well. Also important to us is to have good comparison data of the various types all on the same car and have it be a car that is pushing the limit a lot more than the stock one would. That really is what we have been trying to put together all summer with the silver and white 818R and its roughly 475hp engine. We got to the point of collecting data at the track where the tunnel test became almost a necessity to help determine which way to go from here, and now with that test in hand we have some good direction of what we want to try next.

[Santiago]

I.E., all of the air sources have to have similar pressure capability or you will end up with flow moving between them instead of going through the intercooler. ... Even then, the way the two sources are connected to the plenum can have an adverse effect on how well it performs. Such as in the case where a lot of flex duct is being used. If there is a lot more (particularly if it has more bends) on one side than the other, one can have a negative interaction on the performance of the other (flex ducting has a lot of inherent flow resistance).

This had me worried as well.

Also, flow in a wind tunnel is straight on and uniform, but on track you can go into an extended sweeper (poss. at a yaw angle) which will "unmatch" a matched set of ducts. What I don't know is if this sort of condition could generate an adverse flow that doesn't correct itself once the airflow is straight. I seem to encounter something like this on my daily commute in which I crest a hill and it initiates a flow pattern through the vents and out the sunroof that persists for a long time.

Anywho, I really like the idea of a split plenum that can be customized. Slick solution.

Best,
-j

[Hindsight]

Jim.... slightly related question for you: I think you may be the only people who have started out with a five speed in an 818 and then went to a six speed. Curious to get your opinions on what its like driving the 6 speed vs the 5 speed..... too much shifting or do you like the closer gears? Do you feel the same way about street and track or do you like something different for each?

[shinn497]

Also curious this. And I'm wondering about the weight difference.

[longislandwrx]

any thoughts on ducting air all the way from the front of the car to the rear? rather than moving the intercooler, just run the ducting all the way back feeding the stock location?

[Mulry]

any thoughts on ducting air all the way from the front of the car to the rear? rather than moving the intercooler, just run the ducting all the way back feeding the stock location?

My buddies & I were kicking that idea around last night but there were concerns that the ducting would have to be too large to be practical in this application. It seems like the most efficient solution would be to figure out how to make the existing rear side ducts effective.

[Jim Schenck]

On the transmission side I would say I prefer the 5 speed for the gear ratio spacing, plus it is 64 lbs. lighter and takes a lot less power to spin. (our blue car was down almost 20hp from that switch) The six speeds don't all have the same gearing and the 2007 was definitely nicer than the 2006. For track use we ended up re-gearing our 2006 to give it closer gear spacing in 5th and 6th as we were hitting a wall as soon as we shifted at about 120mph. The six speed does handle a ton more torque though.

Back to the aero stuff, we have kicked around the idea of ducting from the front on the 818R, but it isn't something we tried. I think you could go through the doors on an R with some decent size ducts but it gets tight when you get up around the front tire, on an S I am not sure where you would route the ducting. Our biggest concern was the length and winding path of the duct would limit the flow too much to be any better, but hard to say for sure without trying it. I would say the ducts would have to be as big as you could fit, maybe something like a 5 inch tube from front to back.

[Jim Schenck]

46658

This is how we plumbed the intercooler up to the front, but it was still fairly tight with 2-1/2 inch tubing.

[Hindsight]

Thanks for the transmission info Jim. That's very interesting on the parasitic losses through the 6 speed.

[the_tool_man]

Fantastic information, Jim. Can you use SolidWorks CFD for some of this aerodynamic analysis? I could understand you might not be able to examine the whole car. But for evaluating various scoop and duct configurations, it would seem to be a great first-pass tool that would allow many ideas to be evaluated relatively quickly. Now that you have real-world data from a wind tunnel, you have something to calibrate your analysis results against, right? Either way, I'm really glad to see FF sharing so much information about the development process. Thank you.

[Mitch Wright]

Thanks Jim for the info

[Rasmus]

Jim and Dave,

Thank you for being so open about this. Lovely to see and read all the new information.


Jim, regarding the R and the turbulent flow hitting the rear wing: It looks like the rear roll hoop is causing a bunch of turbulence. Round bars do that. I know you already know that though. So two solutions that I can see. 1. move the rear wing up into clean air. or 2. Put a low drag airfoil around the roll bar so you don't get that nasty turbulence in the first place. Make a sandwich out of fiberglass and install it around the bar.

If you go with the airfoil look into the EPPLER 862, EPPLER 863, or EPPLER 864,

http://airfoiltools.com/images/airfoil/e862-il_l.png
cd at 0 AoA = 0.02828. That's super low.
http://airfoiltools.com/images/airfoil/e863-il_l.png
cd at 0 AoA = 0.03459
http://airfoiltools.com/images/airfoil/e864-il_l.png
cd at 0 AoA = 0.04195

Ultra-low drag as long as it's mostly set at 0 angle of attack. By comparison a circle has a cd (coefficient of drag) of 1.17

[Jim Schenck]

The video doesn't show much of it but we spent a good amount of time with the R and the smoke wand looking at the flow around the bar and how it was affecting the wing. We didn't see as much of a difference as we were expecting between the straight wings we tested and the curved APR that we offer and is on the the GTMs and was on the Blue car. I think the airflow from the cage is the reason for this, you could clearly see that the section of wing sticking out further than the width of the main hoop had much better flow than the area behind the bar, and in the curved wing this is also where the shape is more designed to be pulling airflow from a different direction as it comes off the roof or the humps in the decklid. I feel like the best solution functionally would be to raise the wing above the bar, but since we have to use this car as a demo and a show car it has prevented us from doing that. (lets just say we all aren't quite in agreement on that one:D)

On another car, a modified challenge car, we once made an airfoil around the cage for a track test. The goal in that case was to produce downforce from a part of the car where we already had to have the drag penalty. The result was a car that was undrivable, not from a handling standpoint but because the low pressure under the airfoil was trying to pull the drivers helmet off. Not exactly the same as you are describing but good to know if you try something similar.

[Mulry]

The result was a car that was undrivable, not from a handling standpoint but because the low pressure under the airfoil was trying to pull the drivers helmet off. Not exactly the same as you are describing but good to know if you try something similar.

That had to have been somewhat disconcerting for that driver.

[Rasmus]

On another car, a modified challenge car, we once made an airfoil around the cage for a track test. The goal in that case was to produce downforce from a part of the car where we already had to have the drag penalty. The result was a car that was undrivable, not from a handling standpoint but because the low pressure under the airfoil was trying to pull the drivers helmet off. Not exactly the same as you are describing but good to know if you try something similar.

That's hilarious! Not for the person or people that put into all the work making a custom airfoil to fit around a roll bar at the time. But in retrospect. Hilarious!

Also good to know about the effect a pressure differential airfoil right near the drivers helmet would have. Because, in my dreams, I was thinking about doing that. Now I'll probably just go with a no-lift, low drag, laminar flow, airfoil like I linked above.

[Sgt.Gator]

Regarding turning the roll bar into an airfoil, almost all the class rules I've read make it illegal to have a wing forward of the rear wheels, or more than one wing. You could argue with the tech inspector that it's not a wing, but would probably lose the argument. They aren't going to care if it has zero downforce or not.

There's probably some super-unlimited classes where it could be done, but that's an expensive way to race.

[Canadian818]

Regarding turning the roll bar into an airfoil, almost all the class rules I've read make it illegal to have a wing forward of the rear wheels, or more than one wing. You could argue with the tech inspector that it's not a wing, but would probably lose the argument. They aren't going to care if it has zero downforce or not.

There's probably some super-unlimited classes where it could be done, but that's an expensive way to race.

This will solve everything, lol

http://image.superstreetonline.com/f/34382567+re0+cr1+ar0/modp-1110-03-o%2Bwin-ride-along-chris-rado%2Bworld-racing-scion-tc.jpg

[Frank818]

How funny! But I think if you need such front upper spoiler it means you have an aero design issue to begin with!
Nice, the exhaust is in front of front right wheel. :)

[Mechie3]

That scion set a track record.

[Scargo]

And tires lasted five laps (just guessing)...

[Santiago]

Yeah, that Scion is not a series of mistakes...it's a very well-funded, very fast, serious machine. They've just elected to approach thinking about how to reach their goals in a different way than most folks do. I saw it run once and was just amazed at its speed.

On the matter of a the roll-bar, if you try to "wing-it" (yuk-yuk-yuk), then you might run afoul of the tech inspectors. But that's not the proposal Rasmus (and I) are suggesting. I'm going to build a fairing around it so that it extends into the body. This is no different than what you see on a Radical (or Honda del Sol). The objective is to simply clean up the body and stop the turbulence and you don't need an airfoil to do that - just about any simple ovoid shape is going to greatly diminish turbulence.

I did some basic CFD tests a while back on different fairing shapes and was pretty surprised by the difference anything 5:1 and larger makes - just so long as you're not simply hanging a tail on the backside of the tube. SolidWorks is great for this, but you need the Flow Simulation add in...

Best,
-j

[Mechie3]

Would it be possible to get a photo of just the center grill section all by itself? I can't quite make out the center styling with the stuff behind it. Also wondering what I need to work around to make a new hinge.

[Bob_n_Cincy]

Would it be possible to get a photo of just the center grill section all by itself? I can't quite make out the center styling with the stuff behind it. Also wondering what I need to work around to make a new hinge.
Craig,
There is a builder here in Cincy that just got a coupe with the new nose. I need to stop by and visit him. Are you over this way any time soon?
Bob

[Rasmus]

On the matter of a the roll-bar, if you try to "wing-it" (yuk-yuk-yuk), then you might run afoul of the tech inspectors. But that's not the proposal Rasmus (and I) are suggesting. I'm going to build a fairing around it so that it extends into the body. This is no different than what you see on a Radical (or Honda del Sol). The objective is to simply clean up the body and stop the turbulence and you don't need an airfoil to do that - just about any simple ovoid shape is going to greatly diminish turbulence.

That's exactly what I was thinking. And by calling it a "fairing" I think I could convince a tech inspector that it is body work and not a wing intended to produce down force in between the front and rear wheels.

Even though

http://airfoiltools.com/images/airfoil/e862-il_l.png
the Eppler 862, and

http://forums.pelicanparts.com/uploads8/NACA63520m+labeled1153988124.jpg
the NACA 63+520m

are both airfoils and when made 3d with fluid flowing around them become wings. Their purposes are entirely different.

[Bob_n_Cincy]

Rasmus
Here is some FAIRINGS use on ultralights.
46707

http://www.ultralightnews.ca/streamlinedfairings/1.html

Bob

[Mulry]

Nice find Bob. That's sweet.

[C.Plavan]

This thread escalated quickly.

[Jim Schenck]

46708

This is one with all the openings cut out. They will come shipped with just the upper opening cut and be able to be opened up as needed.

[Sgt.Gator]

If the roll bar is faired in like this it would look great and have no tech issues:
46730

This might be a problem:

https://s-media-cache-ak0.pinimg.com/736x/0f/35/65/0f35655c91040a3a43fd2f267e6d7173.jpg


BTW, this Radical is Subaru powered. Here's how they solved the intercooler problem:

46724.......46725......46727

[Santiago]

Damn, I'm having trouble viewing all but one of Gator's images. Any direct links?

Best,
-j

[Canadian818]

Damn, I'm having trouble viewing all but one of Gator's images. Any direct links?

Best,
-j

I don't see them either

[Mulry]

I don't see them either

They were showing up earlier today, but now none of the ones of the Radical are showing up, just the Chaparral.

[Sgt.Gator]

They were showing up earlier today, but now none of the ones of the Radical are showing up, just the Chaparral.

I think I was over the size limit. I reduced the size and compressed the images more, you should be seeing them now. Let me know if your not.

[Sgt.Gator]

The latest Radical has a dip in the top of the fairing, directly above the intake scoop. I'm wondering if that helps channel air to the scoop? They say this one has the best aero yet.


46731

[Mulry]

I think I was over the size limit. I reduced the size and compressed the images more, you should be seeing them now. Let me know if your not.

Still not appearing. Not even the new one.

[Santiago]

Ditto, can't see them...

But here's a sweet SR3 (showing off the basic concept)

http://www.langeoriginals.com/autos/wp-content/uploads/DSC_3399.jpg

And the street version of the SR8 is pretty enticing (think, wider bar fairing to accommodate both 818 engine cover humps):

http://images.cdn.autocar.co.uk/sites/autocar.co.uk/files/styles/gallery_slide/public/radical-spyder.jpg?itok=cVfvA5-F

[Scargo]

Here's one link for a yellow Radical with a Subaru motor (http://www.precisionchassisworks.com/subaru-powered-radical-sr3.html).
John, from looking at the Radicals I'm puzzled. Puzzled because wind tunnel testing by FFR has not found the Radical's scoop position to be clean air area in the 818. With helmets in the way I am surprised the Radical's design is efficient and effective.
The Radicals intake is similar to a concept I have where I might want to modify the roll bar brace location. Also, with the link you see a front-mounted turbo. Also a plan of mine by using the gas tank area but staying low and exiting the side.

[Mulry]

Depending on the power output goal of the Radical, the necessary efficiency (thus effectiveness) of the Radical scoop may be lower than that which Jim is looking for on the 475hp motor they have in that test mule. A stock+ level tune may be able to make use of the over-engine location with reduced airflow whereas a really boosted motor might need more air to cool the A2A in that location. Just a thought.

I wonder if one were to bring the forward plane of an A2A rear deck scoop flush (or near flush) with the vertical plane of the roll hoop if that wouldn't improve airflow a bit by avoiding the turbulence of the roll bar. Fairing in the entire roll structure is probably the best way to go though, but not easy.

[Sgt.Gator]

Here's one link for a yellow Radical with a Subaru motor (http://www.precisionchassisworks.com/subaru-powered-radical-sr3.html).
John, from looking at the Radicals I'm puzzled. Puzzled because wind tunnel testing by FFR has not found the Radical's scoop position to be clean air area in the 818. With helmets in the way I am surprised the Radical's design is efficient and effective.
The Radicals intake is similar to a concept I have where I might want to modify the roll bar brace location. Also, with the link you see a front-mounted turbo. Also a plan of mine by using the gas tank area but staying low and exiting the side.

Great link Scargo!

I don't know why my images quit working as links from my Google Photos cloud file. It's always worked in other threads. And I can see the images here! There must be a security/privacy/sharing setting on my photo file I need to change.
So I've uploaded them.

[Mulry]

Here's one difference between the Radical scoop and using one on the 818. Look at the airflow off the front of the Radical in this photo:

46735

Versus what the airflow testing was indicating in the recent video from FFR:

46736

I wonder what is the effect of the location of the radiator exit duct on pushing the airflow up. There's a real difference between the Radical and the FFR on that score. We've been playing with this in SolidWorks but nothing conclusive yet.

[Hindsight]

Back to engines......

So the new Ford Focus RS is 2.3L, and makes 350 ft/lbs of torque at only 3200 RPMs. By contrast, the WRX STI has only 290 ft lbs of torque, and it's all the way up at 4,000RPMs, and that's with 2.5L of displacement. The Focus also makes 350HP.

With those kinds of numbers, I'm really curious as to how it's making so much torque so low in the RPM band, and still pulling hard up top. On pump fuel, I don't think I've seen a WRX do anything similar.

[Mulry]

The Focus RS uses a twin-scroll turbocharger. Don't know if it's variable geometry, but that would be another way to expand the range of useful boost.

[Sgt.Gator]

It's also a Direct Injection engine. "Engine technology supplier Bosch says that direct injection can return a 15 percent gain in fuel economy while boosting low-end torque as much as 50 percent."

[Hindsight]

That ecoboost option keeps looking more and more attractive.

[DanielsDM]

Direct injection allows for a higher compression ratio too (9.5:1 on the 2.3L ecoboost) because there is better control of the combustion process.

[AZPete]

"Back to engines" Huh?

[DanielsDM]

Here's one difference between the Radical scoop and using one on the 818. Look at the airflow off the front of the Radical in this photo:

46735

Versus what the airflow testing was indicating in the recent video from FFR:

46736

I wonder what is the effect of the location of the radiator exit duct on pushing the airflow up. There's a real difference between the Radical and the FFR on that score. We've been playing with this in SolidWorks but nothing conclusive yet.

Do you have a SW model of the 818?

[Mulry]

Do you have a SW model of the 818?

This one:

http://www.turbosquid.com/3d-models/3d-2012-factory-818-model/752174

[Santiago]

Back to airflow! [We can do a Bud Light commercial later...]

Those are great comparison pictures Mulry. There are a number of differences in the Radical set up that could account for why they are getting better flow sufficient for their application, not the least of which are (a) lower driver position, (b) smaller cockpit area in general, (c) properly radiused intake scoop entry, and (d) a very different hood strategy. The bar placement is different, the fairings are smoothing airflow aft of the intake (which can actually have a beneficial effect forward of the intake), the scoop itself is higher, etc. Just a lot of differences here that can add up to significant differences in flow. Look at this head-on perspective:

46748

It's a different beastie.

[Santiago]

This one:

http://www.turbosquid.com/3d-models/3d-2012-factory-818-model/752174

Mulry, I have that file as well but I wasn't able to get solid surfaces out of it. I must be doing something seriously wrong with the wizard. If you're willing to help a brother out, PM me.

Best,
-j

[Mulry]

I'd love to help, I'm not the one doing the work. Hell, I'm struggling to learn to do 3D CAD so that I can start printing brackets with the 3D printer. I had a 2D program that I used to use but it's useless in 3D. Different thought pattern required.

Anyway, Roland is doing that. He took that model and then ran wind tunnel simulations in Autodesk Flow Design. Don't know if there was an interim step. I'll check.

[Santiago]

Ah-that may be it. I was setting up to do the CFD analysis in Solidworks, but the turbosquid file options weren't importing well. You need to take the mesh files and convert them into solid surfaces. There's a wizard to help do it, but the automated results were...well, catastrophic. :confused:

[07FIREBLADE]

My 15 WRX puts that power out after being tuned on 91. It's my high boost map though, stock turbo just an intake and turbo back. It's a direct injected motor that's light years newer in tech when compared to the old EJ in the STI that's with 2.0l instead of 2.5 or 2.3l ecoboost. This fact right here was one of the selling points for me not to buy the sti when I got my 15.


Back to engines......

So the new Ford Focus RS is 2.3L, and makes 350 ft/lbs of torque at only 3200 RPMs. By contrast, the WRX STI has only 290 ft lbs of torque, and it's all the way up at 4,000RPMs, and that's with 2.5L of displacement. The Focus also makes 350HP.

With those kinds of numbers, I'm really curious as to how it's making so much torque so low in the RPM band, and still pulling hard up top. On pump fuel, I don't think I've seen a WRX do anything similar.

[Mechie3]

I have the turbosquid models as well. I can import them as surfaces but not as solids. Using the medium or high density point clouds kills my computer.

[nkw8181]

What wizard did you use? I have access to NX but not solid works anymore and it doesn't appear to support obj or 3ds

[Mechie3]

ScanTo3D plugin

[ssssly]

Do the turbosquid models treat the whole car as 1 object or as a series of parts that can be disassembled?

If when the model was scanned (I'm assuming they 3d scanned an 818) it wasn't intended to be treated as a solid, the mesh will not likely be manifold.

One thing you could try is converting the .obj to .stl. There are several web apps that will repair a non-manifold .stl. Some of them will however also then render it as a series of triangles instead of discrete surfaces. Which could cause issues once you compile it for an autodesk fluid simulation. Since an object created with triangles can't have a truly smooth surface.

Once it is manifold though, you might be able to mitigate that be converting it back and texture wrapping it.

Also from looking at the photos, it seems that they rendered all the vents (front grill, side and top) as solid extensions of body panels. So they would need to be removed and the interior paths recreated somehow.

I've been debating getting that model, but $150 seemed a bit much when I could just 3d scan mine as separate parts and have a better model to work from. Unfortunately I have been indisposed and haven't gotten around to scanning it yet.

[DodgyTim]

Older thread on the turbosquid model, developed from photo's?
http://thefactoryfiveforum.com/showthread.php?14844-Anyone-got-FFR-CAD-design&highlight=turbosquid

[LowEndTheory]

Roland here: I am no expert at this but, I am able to run wind tunnel simulations on the TurboSquid model (*.3ds and *.obj) in Autodesk Flow Design. Flow Design meshes the model automatically.

The original model was made in Autodesk 3DS Max, which is more for 3D animations (Avatar!) than accurate CAD or CFD work. It can be taken apart and modified, but there are no vent openings and the grills are just bitmaps. Looks great though.

Since the model is basically solid, I've been mostly using it to observe surface pressures and airflow around areas of the car. I am tweaking the model in 3DS Max by opening up the vents to test intercooler locations, but I am learning this as I go. It can be exported to AutoCAD (and others) and might be a good starting point for you hardcore CAD/CFD people.

[Santiago]

Welcome Roland!

I wish I were a hardcore CFD person. I just have a hardcore program. :cool:
Most of the CFD work I've done is just testing different things (wings, wings in ground-effect, tube profiles, wheels, and one full-car w/rolling ground) to get comfortable with SW Flow Simulation program.

I tried using the same plugin Mechie used, but SW flow simulation requires solids not merely surfaces. I was going to bite the bullet and just start recreating the body in SW using the imported model as a template, but I'm kind of dreading that process (and as ssssly so aptly put it, I've been indisposed as well).

The TurboSquid model is nicely detailed, and for your money you do get quite a few different file formats, but as mentioned, they're mostly graphic related. My computer can handle the medium density files, but the resulting solids I'm getting are still a mess (think of something that looks like a microscopic spore; it's a geometric mess). I've got a low density .obj file in a google.doc if anyone is interested in playing around with it (PM me).

Best,
-j

[LowEndTheory]

I learned that I can look for manifold errors in 3DS Max.

Short version:
If your CFD program is sensitive to this sort of thing, the TurboSquid model isn't going to work without A LOT of work.

Long version:
Each wheel has 7232 open edge errors and the body has 8092. I stopped checking there. Autodesk positions Flow Design as a tool to look at preliminary designs which I guess is why it can afford to ignore/extrapolate these errors during meshing. From their forums:

"If you are looking to examine rough designs/dirty cad (study the what if's) and you don't have time to prepare to use in Simulation CFD then Flow Design is great to get an idea of what is going on."
"If you are looking to really study a wind tunnel analysis in depth with more accuracy and more ability to extract quantitative vs. qualitative data then I would suggest Simulation CFD."

I bet if I try use this model in Autodesk Simulation CFD it would fail as spectacularly as it does in SolidWorks.

[STiPWRD]

I was able to shrinkwrap the .obj surface file I got from Santiago into a solid step file using CREO but the outer surfaces still need to be smoothed out:
46782
On a side note, I've had bad experiences with Autodesk Simulation CFD (formerly CF Design) mainly because it uses a finite element approach and converges based on element criteria instead of other CFD tools, which use finite difference or finite volume, whose convergence criteria is based on energy balance. The autodesk tool could not correlate a simple cold plate pressure drop experiment without tons of fine tuning and the customer service was poor, so I lost confidence in it. I would trust Fluent, Ansys CFX or FloEFD far more.

[nkw8181]

So those with the model would it be usable for interior redesign?

[bbjones121]

My current thinking based on what we have seen testing intercoolers seems to be pointing to different solutions based on the intended use of the car. Testing the air to water systems on the track has shown that with no recovery time they tend to gradually increase in temps over the course of the longer runs, whereas on the street the recovery time at either cruising speeds or idle allows them to stay cooler than either the top mounts or relocated air-to air units still in the engine bay. The two W2W systems we tried were different in that one used a large reservoir and a medium sized cooler and exchanger and the later system used a bigger cooler and a full sized radiator as the heat exchanger with no reservoir. The second system worked better and was overall lighter than the one using the extra tank.

For air to air I still think the top mount is viable for stock and mild builds, on both street and race cars, and that is where we concentrated our street car efforts in the tunnel trying to find the best spots to pull and from and exit air to. The plan going forward for ducting to the top mounts is to use four inlets to feed the intercooler. The two side inlets are effective if they are cut out correctly (the cutout shape made a HUGE difference which was something we missed in our first trip to the tunnel) and either the decklid vents or the roof scoop ducts for the other two depending on which model it is.

During our track testing we also tried several different very large scoops feeding the intercooler from in between the humps and this was not as successful. Even with a large top mount (Turbo XS) the temps were not as low as we would like them to be and the drag/reduced downforce was not good at all. Airflow in that area is just very turbulent and the cockpit itself is a low pressure so air will actually flow backwards into it.

As far as air exit goes the best place is the lower section of the car, the upper vents still allow air to exit but the flow is much slower and more chaotic. The rear trunklid vent is somewhat variable, with the spoiler in place you get air flowing in, but with the wing in place there is not much flow through that vent at all. I still think the vent is useful, particularly for escaping heat when the car is sitting still, but it isn't a good place to get reliable air entry or exit from. Cutting additional vents on either side of the low vent seems to make the most sense for someone needing to get additional air out of the engine bay.

The front mount in the race car is really just going to come down to testing turbo lag. This setup will only be a real possibility for R models as the tubes run through the top of the doors, but the plumbing was actually pretty straightforward and the amount of tube relative to a WRX with a front mount is not that different (maybe 50% more but not 2 or 3 times as much). We stayed with a fairly small inlet tube to try and keep the overall volume down but we still have testing to do to see if this really is the best solution for big power track only cars.

Also on the R, the windscreen makes a big difference, improves drag, downforce, and cooling and running without it does not improve flow into the rear decklid area.


Sorry to resurrect this, but how did you fit a TurboXS intercooler? I can't fit mine under the 818S lid?

[Jim Schenck]

We built a scoop connecting the tops of the humps and then cut out the area underneath the scoop which allowed for the extra size of that intercooler. I would estimate the smallest scoop we had in that location covered about the bottom third of the humps but we also tried larger ones, including all the way to the top of the roll bar. We also sealed the intercooler to the decklid in order to force all the airflow coming in to go through the cooler.

[ssssly]

We built a scoop connecting the tops of the humps and then cut out the area underneath the scoop which allowed for the extra size of that intercooler. I would estimate the smallest scoop we had in that location covered about the bottom third of the humps but we also tried larger ones, including all the way to the top of the roll bar. We also sealed the intercooler to the decklid in order to force all the airflow coming in to go through the cooler.

Was there any appreciable increase to airflow from those configurations?

[lennyspecv]

That's pretty cool to watch testing in a wind tunnel. Never seen that before.

I am optimistic that by the time I have the money for a kit, there will no longer be a need for a AWIC because of improved air flow and ducting.

[bbjones121]

We built a scoop connecting the tops of the humps and then cut out the area underneath the scoop which allowed for the extra size of that intercooler. I would estimate the smallest scoop we had in that location covered about the bottom third of the humps but we also tried larger ones, including all the way to the top of the roll bar. We also sealed the intercooler to the decklid in order to force all the airflow coming in to go through the cooler.

Thanks for the info Jim. I may try welding up my own brackets to drop the back of the turbo xs a bit.

[tmoretta]

Do the two top decklid (Intercooler) vents flow much air? I have improved the flow from these two vents by sealing them to the deck and also sealing the intercooler to the deck. I am wondering if I should add extra scoops on top of the deck vents to capture more air.

[Jim Schenck]

The center decklid scoop did not flow as much air as we were hoping in any of the configurations we tested (determined from post intercooler air temps) and that was even with the windscreen removed completely on an R. The decklid vents are functional and maintain a positive airflow through the intercooler as measured using the wind tunnel flow meter. Our attempt to make these vents flow more air with an extra scoop on top (a scoop from the type 65) did not help the flow although some more tests in that area could likely see some design that shows a benefit. We also have prototype ducts made now for the side scoops which should take advantage of the cutout shape we found worked best in the tunnel.

[bbjones121]

The center decklid scoop did not flow as much air as we were hoping in any of the configurations we tested (determined from post intercooler air temps) and that was even with the windscreen removed completely on an R. The decklid vents are functional and maintain a positive airflow through the intercooler as measured using the wind tunnel flow meter. Our attempt to make these vents flow more air with an extra scoop on top (a scoop from the type 65) did not help the flow although some more tests in that area could likely see some design that shows a benefit. We also have prototype ducts made now for the side scoops which should take advantage of the cutout shape we found worked best in the tunnel.

Sweet! When can we see these prototypes? Carbon fiber option hopefully :)

[Jim Schenck]

This is what we have so far, subject to change after testing of course. The flange on these is set up for 4 inch ducting.
47654
47655

[bbjones121]

This is what we have so far, subject to change after testing of course. The flange on these is set up for 4 inch ducting.
47654
47655

Nice. For some reason I was thinking they were extensions out, but this is perfect. I was trying to figure out a way I could do something like this as I trying to keep the air to air. Please let me know when they are available.

[Flamshackle]

This is what we have so far, subject to change after testing of course.47654
47655

Have you got a testing date for these coming up?

[Jim Schenck]

We are installing these on the coupe we are currently building.

[Lumpyguy]

These bigger vents are what I have been doing. I added 1" to the depth and raised the top line horizontal which opened it up as well. I was looking at putting ducting and tubes up to a shroud on the top of the coolerl. Has any one confirmed just how much air goes thru that side vent?

[Sgt.Gator]

Jim, any updates on all this? I'm especially interested in the side vent solution and the FMIC solution. Any details on the FMIC you can share?

Also, if possible could you post up some of the vehicle weights for the various FF 818 cars here: http://thefactoryfiveforum.com/showthread.php?20190-Post-Your-Weights
Thanks!

[Jim Schenck]

The coupe we built with those side vent scoops was the one with the Ford 2.3 Ecoboost. We figured out as we were building it that the way the intake was routed down low it wasn't practical to use them as a source for the intercooler due to its location on that specific engine. We originally had a mustang intake that had a higher throttle body but was much tougher to package, instead we now have an AWIC mounted under the front of the engine which fit very nicely and helps a little with the higher center of gravity that the inline four has. Our older coupe still has the Top mount so we will retrofit the side vents to it in order to test them, but that will have to be once the spring comes and the roads get clear again.

The race car with the front mount is out at the tuner right now as we are working through an issue with the EFI that held us up during our final test last season. That was the only test we had the front mount installed as the rest of the year we were switching between several AWICs and different configurations of top/remote mount air to air we were wanting to test. Once the engine issue is sorted we will be doing some testing on the dyno with the front mount and then bringing that car down south to do some early season track testing. That will likely be either late March or early April.

[Hindsight]

Thanks for the update Jim. Please let us know where you are going to be racing so we can come watch. Would love to see the 818 at Road Atlanta.

[Mitch Wright]

Thanks for the up date Jim.

[bbjones121]

Thanks Jim

[Sgt.Gator]

Many thanks Jim.

[Sgt.Gator]

Jim,
Any Cd numbers to compare the R with the S? I'm asking because I'm considering an R with an S windshield and full halo cage. It would look similar to a Mazda MX5 Pro Cup car. But I don't want to go down that road if the drag is significantly worse on a S than an R.
Have you tried testing a rear wing on a S ?
Thanks

http://images.hgmsites.net/lrg/2016-mazda-mx-5-miata_100520895_l.jpg

http://images.hgmsites.net/lrg/2016-mazda-mx-5-miata_100520885_l.jpg

http://myroadtrip.net/wp-content/uploads/2015/10/2015-petit-le-mans-mazda-skyactiv-technology-global-mx-5-cup.jpg

[tgf05354]

That's pretty cool to watch testing in a wind tunnel. Never seen that before.

I am optimistic that by the time I have the money for a kit, there will no longer be a need for a AWIC because of improved air flow and ducting.

I too am planning to buy an 818s in a few months. Were can I find more information on ducting for an air to air IC. I'm planning a stock street setup and would like to avoid the complexity and cost of an air to water unit.

[Jim Schenck]

Haven't tried a rear wing on an S, just a couple different heights of spoilers. The drag on an S with a windshield and no spoiler is almost identical to the R with no windshield but with the big wing on the back. On the R the wing adds about 18% more drag, so even though we didn't test that exact combo (an R with a full windshield) and the R cage might have slightly more drag I still think that is a good approximation of the difference. Also though, the windshield will for sure take away some drag and downforce from the wing as well unless the height is raised considerably, so while I think that the windshield adds around 18% drag and the wing adds similar, the two of them together would not likely add up to that total combined.

[bbjones121]

Any updates on the side vent ducts?

[FFRSpec72]

Haven't tried a rear wing on an S, just a couple different heights of spoilers. The drag on an S with a windshield and no spoiler is almost identical to the R with no windshield but with the big wing on the back. On the R the wing adds about 18% more drag, so even though we didn't test that exact combo (an R with a full windshield) and the R cage might have slightly more drag I still think that is a good approximation of the difference. Also though, the windshield will for sure take away some drag and downforce from the wing as well unless the height is raised considerably, so while I think that the windshield adds around 18% drag and the wing adds similar, the two of them together would not likely add up to that total combined.

The windshield on my challenge car takes away about 8MPH at WOT over the windscreen

[Jim Schenck]

Any updates on the side vent ducts?

All the cars are still packed away for the winter except the 818R is out at the dyno. The FMIC in that car is up to be tested next and then we may either test the side ducts on the street car or swap the race car back to a top mount and try them there.

[longislandwrx]

I vote for the latter, I would love my top mount to work effectively on my R.

[Mitch Wright]

I am also running a top mount and will be 100% track ready the end of April early May, I will let you all know if the duct work I am doing is successful.

[nucleus]

Interesting discussion on aerodynamics - it it so counter-intuitive!

High speed is low pressure, low speed air high pressure.

When I built my RV-6A I used a custom cowling and ended up building a plenum for cooling as well.

I actually think that a plenum for the intercooler makes a lot of sense. For best flow keep in mind that you want gentle bell mouth type curves for the high speed air, then increased area for the air to slow down, and once the air is slowed down, it can change direction easier due to reduced momentum.

http://thefactoryfiveforum.com/attachment.php?attachmentid=47654&d=1447785976
Then I look at this image, the transition into the oval section looks too abrupt, but with the strange magic of moving air, perhaps that abruptness is what makes it work.

http://www.knology.net/~rv7rotary/Oil_cooler_duct_under_prop_-_very_good.JPG
Here are some examples of ducts that slow the air down and increase pressure.
http://www.improvedracing.com/images/products/OCD16_lg.jpg
Not great, but better than most

http://www.rotaryeng.net/rad-taps.jpg
Here is a simple way to test your airflow mods, you hot glue some sponge onto tubing

http://www.rotaryeng.net/manometer.gif
and use a water manometer to measure static pressure from the changes you make.

So-called NACA ducts were designed for high speed aircraft to feed turbojets that were already sucking air. They are not appropriate for anything but a APU turbine on a big jet.

[Frank818]

So-called NACA ducts were designed for high speed aircraft to feed turbojets that were already sucking air. They are not appropriate for anything but a APU turbine on a big jet.

Why are they used on race cars?
What would you suggest as a replacement to flow air in with minimal drag if NACAs are crap for cars?

[bigAl]

"So-called NACA ducts were designed for high speed aircraft to feed turbojets that were already sucking air. They are not appropriate for anything but a APU turbine on a big jet."
I would respectfully disagree. They have been successfully used on many non-jet airplanes and certainly on many automobiles.

[Sgt.Gator]

That must be why the crappy Ferrari aero engineers use them.

https://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Ferrari_F40_in_IMS_parking_lot.jpg/1280px-Ferrari_F40_in_IMS_parking_lot.jpg

[Mechie3]

It's actually quite the opposite. They were intended for feeding jets, but did a poor job at that and are better where lower flows are needed.

From a few different sources:

Designed in 1945 by the National Advisory Committee for Aeronautics (precursor to NASA), the NACA duct was intended as an air inlet for jets. Only it was a failure. The design wasn’t any good for bringing fast, “clean” air into the fussy, rotating impeller blades of a jet engine, so the engineers who invented it lost interest. Luckily for today’s racers—and many generations of Italian sports cars—the qualities of the NACA duct that made it unfit for jets make it ideal for most other kinds of engines, and its low profile, simplicity, and small size earn it love from designers for aesthetic reasons.

And:

The original goal of the NACA duct was not applications requiring maximum pressure recovery (ram pressure), unlike the prominent ram-type intakes seen behind the driver's head in Formula One cars. The application was intended for applications where is desired to minimize the parasite drag added to the aircraft or car. This works well for air vents and such as the drag remains low whether the vent is opened or closed. It is not very useful for engine air intakes, bur is useful for cooling air supply. They are low-drag intake channels used mostly for a variety of cooling requirements such as brakes, engine, and for driver cooling intake. Distinctive geometry includes a widening mouth at the inlet, with the duct floor slightly opening up the flow area.

[Frank818]

I'm going to use one on the top side of the hump to feed my air intake filter, but it's an addition to using the side scoop as well for the air intake, I'll use both air sources and only the top, right from the hump, will have a tiny NACA duct in order to open up more the duct floor and bring more air. I think it'll work, although we haven't seen much of wind tunnel results on these 2 818 top side scoops.

[mindinclouds]

That must be why the crappy Ferrari aero engineers use them.

https://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Ferrari_F40_in_IMS_parking_lot.jpg/1280px-Ferrari_F40_in_IMS_parking_lot.jpg

They do work well if sized, shaped and located properly...

Note the sharp corners along the longitudinal edges of the inlet. These are very important in developing a vortex off of the edge and rolling towards teh inside. I see NACA vents all the time (even on cars built by high tech racing teams) that have the corners nicely radiused (I guess it seems logical that they would be better if shaped that way, but if you read the old NACA documents it explains just the opposite).

[mindinclouds]

I think it'll work

Keep in mind that a NACA duct will not work very well at any location with an air pressure below ambient.

A common example is any surface that is more than a rather large outside radius when the surface is diverging inward.

[UnhipPopano]

Out of curiosity, if FF has been "Testing" the side and rear vents, did they try changing the shape of the openings to the NACA duct shape, and if so did it reduce the drag?

[tmoretta]

Do you have a pic. of the side inlets "correctly cut out"?

[bbjones121]

I would love to know whatever happened to the Factory five ducts that were being developed.

[longislandwrx]

yup bump for FFR updates.

[Sgt.Gator]

Bump! Any update on these side scoops?

[AZPete]

Gator, I'm not sure which side scoops you are asking about, but I have the FFR ducts that collect/direct air from the side vents in front of the rear wheels. I like them on my street 818C and they are available from FFR. Here's my thread about the ducts:

http://thefactoryfiveforum.com/showthread.php?24413-818C-Intercooler-Plenum&highlight=818+Intercooler

[Sgt.Gator]

Thanks Pete. Good read.
I'm trying to figure out if the fiberglass scoops I can order from FF are the same design as Jim tested in posts #24 and #25 in this thread.

[AZPete]

Gator, in #24 and #25 Jim seems to be showing that the knife-edge of the vent increased flow. In #41 he is thinking of a duct and in thread #131 he shows the duct they made for the inside of the side vent. The 2 ducts Jim sent to me to test look just like the fiberglass duct in thread #131. I believe those are the same ones now offered on the FFR web site. Also in this thread about aero, I forgot who, but someone said the 2 side vents have a combined area of 65 sq. in. which is about the same as the OE WRX hood scoop. So, pulling air from both side vents plus the roof vent, I'm getting lots of air to my A2A intercooler as shown in the dual IAT gauge. Again, however, my 818C is a street car so WOT is brief.

[Sgt.Gator]

Thanks Pete!

[alpine227]

My current thinking based on what we have seen testing intercoolers seems to be pointing to different solutions based on the intended use of the car. Testing the air to water systems on the track has shown that with no recovery time they tend to gradually increase in temps over the course of the longer runs, whereas on the street the recovery time at either cruising speeds or idle allows them to stay cooler than either the top mounts or relocated air-to air units still in the engine bay. The two W2W systems we tried were different in that one used a large reservoir and a medium sized cooler and exchanger and the later system used a bigger cooler and a full sized radiator as the heat exchanger with no reservoir. The second system worked better and was overall lighter than the one using the extra tank.

For air to air I still think the top mount is viable for stock and mild builds, on both street and race cars, and that is where we concentrated our street car efforts in the tunnel trying to find the best spots to pull and from and exit air to. The plan going forward for ducting to the top mounts is to use four inlets to feed the intercooler. The two side inlets are effective if they are cut out correctly (the cutout shape made a HUGE difference which was something we missed in our first trip to the tunnel) and either the decklid vents or the roof scoop ducts for the other two depending on which model it is.

During our track testing we also tried several different very large scoops feeding the intercooler from in between the humps and this was not as successful. Even with a large top mount (Turbo XS) the temps were not as low as we would like them to be and the drag/reduced downforce was not good at all. Airflow in that area is just very turbulent and the cockpit itself is a low pressure so air will actually flow backwards into it.

As far as air exit goes the best place is the lower section of the car, the upper vents still allow air to exit but the flow is much slower and more chaotic. The rear trunklid vent is somewhat variable, with the spoiler in place you get air flowing in, but with the wing in place there is not much flow through that vent at all. I still think the vent is useful, particularly for escaping heat when the car is sitting still, but it isn't a good place to get reliable air entry or exit from. Cutting additional vents on either side of the low vent seems to make the most sense for someone needing to get additional air out of the engine bay.

The front mount in the race car is really just going to come down to testing turbo lag. This setup will only be a real possibility for R models as the tubes run through the top of the doors, but the plumbing was actually pretty straightforward and the amount of tube relative to a WRX with a front mount is not that different (maybe 50% more but not 2 or 3 times as much). We stayed with a fairly small inlet tube to try and keep the overall volume down but we still have testing to do to see if this really is the best solution for big power track only cars.

Also on the R, the windscreen makes a big difference, improves drag, downforce, and cooling and running without it does not improve flow into the rear decklid area.

Good afternoon, have you folks done any testing on sidemount configurations?

[fastzrex]

Gator, in #24 and #25 Jim seems to be showing that the knife-edge of the vent increased flow. In #41 he is thinking of a duct and in thread #131 he shows the duct they made for the inside of the side vent. The 2 ducts Jim sent to me to test look just like the fiberglass duct in thread #131. I believe those are the same ones now offered on the FFR web site. Also in this thread about aero, I forgot who, but someone said the 2 side vents have a combined area of 65 sq. in. which is about the same as the OE WRX hood scoop. So, pulling air from both side vents plus the roof vent, I'm getting lots of air to my A2A intercooler as shown in the dual IAT gauge. Again, however, my 818C is a street car so WOT is brief.

Hey Pete, what do you use for 'cold air' source to the inlet for the engine? I was anticipating use of the roof duct for inlet air and the side scoops (with FF inserts) for oil cooler/compartment cooling.

[AZPete]

Mark, I'm still drawing intake air from the duct inside the right side vent. This right-side vent also feeds air through a 3-inch flex tube to the intercooler plenum, however. Most of the time cool air is sent to the intercooler and to the engine intake filter, but at WOT the engine sucks so much more air that it causes the flow in the tube to the intercooler to reverse, thus sucking air from the intercooler. I haven't changed it yet because I don't know what's best. Plus, this is a street car with only occasional WOT, so I wonder how bad this is.

I think the roof ducts would work well for your engine intake since the OE intake is 3-inch and the roof ducts are two 3-inch ducts, fed by the roof vent of (?)sq.in. I assume you have an A2W intercooler.

See Post #3 in this thread:
http://thefactoryfiveforum.com/showthread.php?24413-818C-Intercooler-Plenum

[fastzrex]

Mark, I'm still drawing intake air from the duct inside the right side vent. This right-side vent also feeds air through a 3-inch flex tube to the intercooler plenum, however. Most of the time cool air is sent to the intercooler and to the engine intake filter, but at WOT the engine sucks so much more air that it causes the flow in the tube to the intercooler to reverse, thus sucking air from the intercooler. I haven't changed it yet because I don't know what's best. Plus, this is a street car with only occasional WOT, so I wonder how bad this is.

I think the roof ducts would work well for your engine intake since the OE intake is 3-inch and the roof ducts are two 3-inch ducts, fed by the roof vent of (?)sq.in. I assume you have an A2W intercooler.

See Post #3 in this thread:
http://thefactoryfiveforum.com/showthread.php?24413-818C-Intercooler-Plenum

Thanks again, Pete, for your input. I want to run A2A IC in the stock position, just trying to reduce complexity where possible (and weight). Like you, this is a primarily a street car, and WOT will be a rarity for more than a few seconds. Having a single plenum is attractive as it also reduces complexity; I have followed your experiments in airflow and it is interesting that the engine sucks so much air when 'on full song'.

Are you running an oil cooler? How are you ducting air to it?

And one more time, thanks for the A/C install documents. It removed a lot of routing/location mysteries!

[AZPete]

Mark, I'm not running an oil cooler other than the stock cooler/heater/whatever at the filter. Thousands of WRXs seem to be fine driving streets in lots of conditions, so I don't know why I would need any other oil cooler.

I was stupid to install 2 fans in my intercooler plenum, and will remove them. I put them in thinking I'd need them to move air when stopped or in stop-&-go traffic. But, at those times, the turbo is not heating the intake air and the engine is sucking ambient air through the intercooler, so having the fans push ambient air is useless. When my 818C is moving, I've got plenty of ambient air coming through the roof and side ducts to cool the intercooler.

Regarding appearance, I like the suggestion by ben1272. He said to make 2 narrow plenums, each leading from the roof ducts back to the intercooler. They would look sort of like the intakes on bigger engines. Good idea for another project.

[frankc5r]

Pete,

Think u are headed in right direction.
I have talked to turbo experts who
can prove with math/modeling/tests
that you only need about 30 mph air
speed for full cooling on air/air ic.
Of course higher is better especially for racing but
30 works for a strong street setup.

[fastzrex]

Mark, I'm not running an oil cooler other than the stock cooler/heater/whatever at the filter. Thousands of WRXs seem to be fine driving streets in lots of conditions, so I don't know why I would need any other oil cooler.

I was stupid to install 2 fans in my intercooler plenum, and will remove them. I put them in thinking I'd need them to move air when stopped or in stop-&-go traffic. But, at those times, the turbo is not heating the intake air and the engine is sucking ambient air through the intercooler, so having the fans push ambient air is useless. When my 818C is moving, I've got plenty of ambient air coming through the roof and side ducts to cool the intercooler.

Regarding appearance, I like the suggestion by ben1272. He said to make 2 narrow plenums, each leading from the roof ducts back to the intercooler. They would look sort of like the intakes on bigger engines. Good idea for another project.

Thank Pete for your input. I will monitor the oil temp in the sump and see what happens. And thanks for the update on the plenum fans, with all your experimental data, you are helping us all about air through the A2A IC on top.

You talk about two narrow plenums from the roofs ducts, and can not visualize the result. I am getting close to first start and then will need to manufacture plenums.

[Sgt.Gator]

I'm bumping this 5 year old thread because there are a lot of new builders who have never seen it and can benefit from what's in here.