Any ABS updates? Anyone have it working?

[Hindsight]

I've read through literally all of the ABS threads in this subforum, and I've been keeping up on most of the build threads for a few months now. I'm still unsure as to how doable it is.

From what I understand, Wayne may be the only person to have done it on a car that is currently running and driving. However, I don't see any update in his thread about how/if it is working or what he had to do to the software to make it work; there is just one post that shows the ABS valve body plumbed in.

Having read all the ABS threads and having a basic understanding of ABS, it all seems pretty straight forward to me with one exception: Different diameter wheels and tires between the front and back. I have read the talk here and on other forums that this will cause problems in the ABS computer (which makes sense) but that this issue can perhaps be adjusted in the ABS controller. Does anyone know if this is true and if so, what is involved in doing it? Is it something you could do with an AccessPort?

[Quiny]

I was planning on incorporating ABS in my build but just recently decided against it. My reason was that when I researched the ABS from my year donor (2002) there was nothing but problems related to it. They even had some kind of recall. I also read that it was corrected in later years. The problem was that it would activated (prematurly)during braking if you hit a bump while braking and would not stop unless you reapplied the brake. Many people described it like loosing the brakes altogether. I never found any information on reflashing it or adjusting sensitivity. If I had a newer year donor I would have probably used them.

[Goldwing]

I am using ABS. After plugging in everything, the ABS light on the dash went out, so at least the internal checks are passing. Plumbing was pretty straight forward. I put the g sensor on the floor at the rear of the center console. The forward foot on the 1" lateral square tube behind the seat, the rear foot on the floor where the stock gas tank would sit. The g sensor isn't required for ABS to work I believe, but is needed for the higher functions to work like electronic brake distribution maybe even some traction control functions. I started with same diameter wheels all around to be sure, but if it is determined a small difference doesn't seem to affect operation, I'll likely go up a size in the back to aim for a larger contact patch and lower revs. For the small differences in tire sizes pretty much everyone is talking about, the guys who would know are assuring us not to worry. I'm not on the road yet, but I'll report back when I am. Figured the dash idiot light going out was worth mentioning. My donor is an 07

[AZPete]

I kept the ABS and I have go-karted for 2 miles around the neighborhood but I have not yet been able to try a skidding panic stop to test the ABS. I've got plenty of power but not enough space . . . yet. It's back in the garage for some wiring work now but soon I'll scare the neighbors with some hard stops to try the ABS. Stay tuned.

[Hindsight]

Thanks for the replies guys. My donor is a 2007 so it shouldn't have the ABS issues that bother the older models.

For those that do have it working, please post front vs rear tire diameters. I'd like to know how much variance is acceptable without having to mess with the ABS control module programming.

Also, can you defeat traction control with an Access Port?

[sponaugle]

Thanks for the replies guys. My donor is a 2007 so it shouldn't have the ABS issues that bother the older models.
For those that do have it working, please post front vs rear tire diameters. I'd like to know how much variance is acceptable without having to mess with the ABS control module programming.
Also, can you defeat traction control with an Access Port?

I have not yet seen anyone who pulled the flash images off the exiting ABS controller. It should be possible as the ABS controller does SSM2, and the Subaru Select Monitor shows a 'programming ABS' option. If someone has a Subaru Select they can play with I can get a capture of the flash protocol.

If I recall correctly there is no 'traction control' on the 07 WRX. The 08 STI and WRX added the traction control and VDC system (Which can still be disabled via a button). In the case of the 08 STI, the TC system is controlled by the ABS system, and the ABS system calls for reduction in torque from the ECU via CAN bus. The ECU by default uses throttle control to reduce output torque, and currently the access port does not have the ability to edit those maps and algorithms. The VDC system uses the ABS system to apply paratial brake pressure to specific wheels based on yaw, accel sensor, steering angle sensor, and a few other things.

[Goldwing]

Hmm. Steering angle sensor. I wonder if mine is centered, assuming it is in the steering wheel area? No wires anywhere else. I wonder what the chances are the wheels were centered when it was removed from the donor? I remember putting it on centered and was careful not to turn it while it was off the car. Something else to research.

[Hindsight]

Thanks for the info Jeff. Messing with the ABS programming seems like it might be complicated but if that's what has to be done then that's what has to be done. I wonder how much of a difference in tire diameter the stock system will take and still function properly without throwing a code? I'm hoping 24" in front and 25" in back will be ok. I'm pretty sure that is the maximum variation most 818 owners will have so if that works, then everyone should be good.

[Oppenheimer]

It occurs to me that people put different wheel & tire sizes on modern cars all the time, including WRX's, and I've never seen on any forum anyone complain or search for a solution to ABS issues caused by mismatched diameters. Its entirely possible this is a big deal and I've just never heard of it. But I'm thinking its not really a problem.

People have also worried/speculated that since 818 is radically changing the weight and more importantly weight distribution, and wheelbase, etc, it will cause issues trying to run ABS. But I'm thinking a skidding wheel is a skidding wheel. ABS senses it regardless of any of those factors. I suppose its possible the way it tries to unlock the wheel won't be ideal, the frequency of pulses used, etc, due to those factors. But its still got to be better than no ABS at all (for the reasons/circumstances one would want ABS on a car like this, which, yes, all you driving purists, there are still good reasons for it. Especially since disabling it can be a button press away.)


As for traction control, on another, not WRX related forum I frequent, owners there report good results reprogramming the ECU not to cut power when traction control engages. The ABS still does its thing to apply individual brake to make directional corrections, but power is not reduced. This somewhat diminishes the effect of traction control, which can be good or bad depending on circumstances. But the key is it doesn't affect power output. Not sure if that is possible (or useful) with WRX powertrain (or if it would be different with that powertrain in an 818.) Something to think about I suppose.

[Goldwing]

Bob put a helpful excerpt from a subie manual on my build thread at post 55, page 2 I think. It mentioned the ABS kicks in at 8% wheels speed difference. Figure out wheel speed differences for your staggered setup and run the percentage. Leave room wheel speed differences for tight bends in the road.

http://thefactoryfiveforum.com/showthread.php?13026-Goldwing-s-818-Street-The-Phoenix/page2

[Kurk818]

Jeff - I know the STI came with the steering angle sensor but looking over the WRX wiring diagram i did not see one as part of the system. I have switched my ABS pump to a non STI one and am incorporating the components/changes to the STI wiring.

Am i wrong in thinking that the steering angle sensor is a STI only component? As well as the yaw sensor.


I have not yet seen anyone who pulled the flash images off the exiting ABS controller. It should be possible as the ABS controller does SSM2, and the Subaru Select Monitor shows a 'programming ABS' option. If someone has a Subaru Select they can play with I can get a capture of the flash protocol.

If I recall correctly there is no 'traction control' on the 07 WRX. The 08 STI and WRX added the traction control and VDC system (Which can still be disabled via a button). In the case of the 08 STI, the TC system is controlled by the ABS system, and the ABS system calls for reduction in torque from the ECU via CAN bus. The ECU by default uses throttle control to reduce output torque, and currently the access port does not have the ability to edit those maps and algorithms. The VDC system uses the ABS system to apply paratial brake pressure to specific wheels based on yaw, accel sensor, steering angle sensor, and a few other things.

[Goldwing]

Jeff - I know the STI came with the steering angle sensor but looking over the WRX wiring diagram i did not see one as part of the system. I have switched my ABS pump to a non STI one and am incorporating the components/changes to the STI wiring.

Am i wrong in thinking that the steering angle sensor is a STI only component? As well as the yaw sensor.

Looking into this more and rereading the post you were referring to, I believe you to be correct, and Sponaugle. He mentions, and I forgot this by the time I got that far into the post , 08 onward using steering angle with the introduction of traction control and vcd. So, 07, my year, and prior WRX's will not have a steering angle sensor for that. Finally, looking over the wiring diagrams, and to be clear I am not an electrical engineer, it appears only STIs have a steering angle sensor which is not used by the ABS system, but rather with the DCCD system running the center diff. That's what I came up with anyway. Looking for connector B426, I came up empty on my car. I checked the wire colors to be sure. At one point, I had the immobilizer antenna that surrounds the ignition switch marked as B426, but later corrected it. I guess that plug is STI only.

[Kurk818]

Ok, Good to have an extra eye on it. Now as far as G sensors go on a WRX; is there 2 or one? One in the center console and one up front?

[Goldwing]

That I know of, yes. The center console for ABS and brake distribution logic. Then one inside the airbag module as a check against the crash sensors. Both, airbag g sensor and a crash sensor must trip to get an airbag to deploy. There are four crash sensors, 2 in front, then 1 each B pillar. I've heard those referred to as g sensors too, so trying to be thorough. As a ridiculous relatively new dad, airbags are on my wish list, but I have no idea if I'll get the system to work yet. Ridiculous, I know, lol, I blame the daddy instincts.

[Hindsight]

Interesting..... do you know if you can get away with just having the center console G-sensor in place, for ABS, or do you need to hook the ABS into the airbag module in order for the ABS light to stay off?

[Goldwing]

Airbag module is not needed for ABS. Once I plugged the center console g sensor in and all 4 corner wheel sensors, my ABS light went out. The g sensor in the airbag module is just to check and verify the crash sensors.

[Hazelwwp]

I need help with the ABS system. I have not driven the car to determine if the ABS is working but I know the Park Brake light and the ABS light on the combination meter are "ON". Both these lamps are driven by the ABS controller. Pin 8 must be pulled low to turn "OFF" the Parking Brake Warning Light. Pin 22 must be pulled low to turn "OFF" the ABS Warning Light. I have tested the wiring by jumping these pins to ground (at the ABS controller connector) and the lamps go off as they should so the wiring is OK. The ABS Controller is not pulling these signals low for some reason.

I have tested the input wiring to the ABS controller and all appears to be working properly. Specifically,

A. I monitored each wheel speed sensor at the ABS controller connector while rotating the tires and could observe the frequency input correctly for each wheel.

B. I checked each wire from the G sensor to the ABS controller connector and it is wired correctly. Then I checked the open circuit impedance from the ABS Controller connector between pins 10 and 21. I measured 3.7 K-ohm which is perfect.

So — no problem with the inputs or wiring. The problem has to be the ABS controller itself.

I do not have access to a Subaru Select Monitor but I have a generic scanner (Snap-On Ethos). The scanner allows me to select whether I want to monitor the (1) Engine, (2) Transmission, (3) Antilock Brakes, (4) Airbag.

When I select “Antilock Brakes”, I am asked to select the transmission “AT or MT”. After selecting the transmission, I am taken to the “Main Menu (ABS)”. From here I can select:

Data (No Codes)
Codes Only
Clear Codes

After selecting “Codes Only”, I have to select if I want to see “Current Codes” or “History Codes”. In both cases the scanner reports

***No Current DTC’s Present***”, or
***No History DTC’S Present***

However, when I try to look at the live data, the scanner reports that it is “collecting data” then flashes an error message too briefly to read it and then starts over. Bottom line, I can’t read the data and I question the lack of reported DTC’s.

I desperately need to read the data. Does anyone have a solution?

[Goldwing]

If you hear the headlight relays when operating the ebrake, then the abs system is very likely holding you back, as you surmised. I had both (ABS and brake) lights until plugging in my wheel speed sensors. Then they both went away. Besides the obvious checking each plug for corrosion, did any particular corner get hit on your donor? Perhaps the wheel sensor in that corner has a little damage causing an intermittent failure? Do you have a meter that can sense a short duration abnormality in the wheel speed sensor output. Could be a spot to focus on?

[Goldwing]

Is your brake fluid reservoir level sensor plugged in? Deleted? If deleted, how did you delete it? I believe open circuit was the satisfactory condition to make the light happy.

[Hazelwwp]

The Subaru manual is not 100% accurate. The Subaru manual showed a “Reversing Circuit” in the input from the parking brake switch and the brake fluid level switch but this is not correct. Following is a corrected sketch (See Attached JPG).

Note that the inputs function as follows:

Parking Brake Switch -- Low to turn “Parking Brake Warning Lamp” ON

Brake Fluid Level Switch --Low to turn “Parking Brake Warning Lamp” ON

Generator Switch -- Low to turn “Charge Warning Lamp” and “Parking Brake Warning Lamp” ON

Pin 8 of ABS Controller -- Low to turn "Parking Brake Warning Lamp" OFF

Pin 22 of ABS Controller -- Low to turn “ABS Warning Lamp” OFF

I have confirmed the circuits function as described above (and shown in the sketch) and I have tested all the inputs including the brake fluid level switch. The only problem is that the ABS controller is not pulling Pin 8 or Pin 22 to the low state.

[Bob_n_Cincy]

Currently we have our abs plumbed but not wired electrically.
We have done about 75 autocross runs and paid particular attention to our braking.

Our Setup:
We are running square brakes. What I mean by that is that we are running the same calipers on all four wheels.
Four front dual piston (1.685 dia) sliding calipers (not brembo).
Front rotor 24x294mm (11.57") ventilated
Rear rotor 18x290mm (11.42") ventilated
StopTech Street Performance Brake Pads,Para-Aramid Material (no fade)
No proportional valve.
No power brake booster.
Subaru oem dual master cylinder
pivot point on brake pedal moved up 3/4"

Our theory:
Front engine cars are heavy in front and weight shift to the front during heavy braking. They have twice the weight on the front wheels during braking compared to the rear so the front brakes are twice as big as the rear.
The 818 is rear heavy and has a low center of gravity. The rear is heavier than the front and with the low CG only a small amount is shift to the front wheels. I estimated that the weight was the same on all four wheels during braking.

Our Results:
During running on the course we have seen very little lock up. I estimate 60mph to 30mph hard transitions going into turns.
During the stop after the finish line we were simulating panic stops at 80 mph. The rear tires would bark just for an instant then grip. The car stops very quickly with full friction on all 4 tires.

Conclusion:
Our setup is very close now. So no priority to do anything right away.
Option 1: Ditch the ABS unit and add Proportional valve (95% open) to the rear brakes.
Option 2: Wire up ABS unit.

Note: We had to do some custom fabrication (drilling and grinding) to use front calipers on the rear.

Let me know if you have questions.
Bob

35752

[Turboguy]

Sounds like you guys have a good handle on your car's current braking abilities and tendencies, Bob. Have you done any trail braking on the track with it? On a more unrelated note, I'm also curious how the car responds when you lift in a turn?


How difficult would it be to wire up the ABS/EBD unit and give it a try? Could solve the (not so serious) rear brake issue for you and add some stability when braking on mixed surfaces.

[tmoretta]

Although I have not driven the car yet, my running "go cart" does have the Subaru ABS system installed. Only problem we have run into so far was a constantly lit ABS fault light in the combination meter (gauges). After much research and diagnosis, we finally determined that the brake light switch must be functional, and the stop light bulbs must be wired and installed. Then you can clear the fault codes at pin six of the ABS diagnosis connector (B82).

[Bob_n_Cincy]

Sounds like you guys have a good handle on your car's current braking abilities and tendencies, Bob. Have you done any trail braking on the track with it? On a more unrelated note, I'm also curious how the car responds when you lift in a turn?
How difficult would it be to wire up the ABS/EBD unit and give it a try? Could solve the (not so serious) rear brake issue for you and add some stability when braking on mixed surfaces.

Hi Turbo Guy,
Michael and I have 2 different driving styles.
I brake for the appropriate speed for the turn then coast through the turn.
Michael waits longer to brake, using the brake to plant the front end for turn in. (Michael is faster)

Your question "I'm also curious how the car responds when you lift in a turn?" we are usually not in the gas in the turn unless it is a long sweeper or slalom. If the back end kicks out in a turn, it is quick. Some times lifting saves it, sometimes not, stay in the gas and drifting out has worked also.

Biggest problem is getting into the gas coming out of the turn. If the turbo (td04) kicks in before you are straight, your going around. We are going to try bigger rear tires at lower pressure to correct this.

Our 04 forester XT did not have EBD.
It would take 2 days to build the abs harness and another day to install.
Getting it working may be another issue. Our ABS had a CAN bus communications to the automatic transmission TCM (deleted). No telling How it will react to that.
Bob

[Kurk818]

I have my car up and running with a full STI swap. I did use a WRX ABS pump and got rid of the steering position sensor and DCCD connection.

I did not hook up the proportioning valve. The front tires lock up. I dont feel like its braking the way it should. Gearing down has the greatest effect on braking. Any suggestions on what to try out?

ABS light is on BTW

[Samiam1017]

Bob what rear rotors are you running?

[Bob_n_Cincy]

Bob what rear rotors are you running?

CENTRIC Part # 12147025
http://www.rockauto.com/catalog/moreinfo.php?pk=2034296&cc=1435927
$18.58 at rock auto
There is a couple of issues I had to address on this mod.
The rotor is 1/4" thinner than the front rotor. So I added a 1/4" plate to the back of the outside pad.
Also the pad hangs off the top of the rotor by 3/8". I may do some more customization to the pads.
Bob

[Evan78]

Bob, was it not possible to locate the new rear calipers such that you could use rotors identical to the fronts?

I had the same thoughts on the brake system and I'm glad someone is ahead of me in validating the theory that much more rear brake is not a waste.

It would be great to see you get the ABS system functional.

[Bob_n_Cincy]

Bob, was it not possible to locate the new rear calipers such that you could use rotors identical to the fronts?
I had the same thoughts on the brake system and I'm glad someone is ahead of me in validating the theory that much more rear brake is not a waste. It would be great to see you get the ABS system functional.

It would be much easier if I was willing to get rid of the ebrake. Then I could put front rotors on all four wheels.
I still might do that but I would add a small caliper style ebrake.
Bob

[Louisromersh]

Hey all so I don't remember reading this some ware but is there a specific modle year I should avoid
if I plan to use ABS. I believe it was 2002 but does this apply also to 2003 wrx.

Thanks

[bbjones121]

Nobody has this working yet?

[Hindsight]

At least two people have it installed, but no one has tested and replied back with results yet. :eek:

[AZPete]

My ABS works great! As I posted in the brake line thread, though I'm not licensed I tried 8 hard stops from 60 mph on the private streets of my neighborhood. (No complaints . . . yet) It stops very quickly, stays straight with no skidding, and I can feel the pulsating of the ABS. My 818S has stock 06 WRX calipers, master, ABS module and stock/dieted wiring to ECU and wheels. I have a proportioning valve on each front brake line but so far both are set to full open. The fronts grabbed evenly and I couldn't tell how much the rears were contributing but they didn't squeal. I'm happy because if the ABS didn't work I don't know where I would start trouble shooting!

[Hindsight]

Nice, thanks for the followup. So we have two confirmed people with working and tested ABS now. One with OEM brake line and sensor routing using two front prop valves, and one with switched routing of brake lines and sensors so one master cylinder feed line controls the front brakes and has a single prop valve between the master and ABS module.

[matteo92065]

Make that 3.
Mine is working and tested.
06 WRX, two proportioning valves on front wheels, STI calipers on front, WRX rear. Stainless lines
I have a switch to turn ABS off.

[vrumpsh]

Make that 3.
Mine is working and tested.
06 WRX, two proportioning valves on front wheels, STI calipers on front, WRX rear. Stainless lines
I have a switch to turn ABS off.

Any way you can post pictures of the way your routed the lines around on the front?

[Hindsight]

Check my build thread - I have pics of all the brake line routing, including ABS and dual proportioning valves.

http://thefactoryfiveforum.com/showthread.php?15217-Hindsight-s-build-thread&p=209137&viewfull=1#post209137

[bbjones121]

Same.

[svanlare]

One more to add: svl-818&p=181252 (http://thefactoryfiveforum.com/showthread.php?13965-svl-818&p=181252&viewfull=1#post181252)

[DMC7492]

Hi guys after hearing the results of having the proportioning valves wide open,I decided to run ABS without the valves, so I have the stock hydraulic system. With my front mount tank weight is more up front.
The brakes are Wilwood 12 up front and the 12.125 on the rear. Not driving yet but very close.
Four wheel sensors to wire ,then a few items on the punch list before carting, weather being the major set back its still cold up here. Some pictures of the ABS unit and lines.
51287
51288

[longislandwrx]

DMC7492 nice work, nice clean bends.

[DMC7492]

Hi Guys I am oficially Go carting now. Have 102.4 illegal miles on country roads logging my fuel system and engine timing. Runs well up through 80 miles an hour, handles great on smooth roads! I also tested my stock antilock brakes with the Wilwood system from 25 MPH with the right wheels on the pea gravel on the side of the road stopping was non eventfull and straight. Slight buzzing as the soleniods did thier work. Then at 40 MPH on asphalt roads with pea gravel at stops from the Winter traction agent and again straight stopping and solenoid actuation . One more test at 55 MPH and stopping was quicker than I expected! I was 30 feet from the intersection!!. The wear on the brake rotors E coating show the fronts are doing more work as the coating is about two thirds worn off and the rears about one half worn off. This again is the stock hydraulics with NO proportioning valves in the front or rear wether it be the stock ones or aftermarket.
I am very impressed in the results I am experiencing! This is out of the 2005 WRX Sedan donor, But not responsible for any results you may experience!!

[Hindsight]

Thanks for posting results. Glad its working well for you. I still need to test mine.

[Hindsight]

Thought I would followup on this thread.

I tested my ABS system very well, and very often at the race track (Road Atlanta) two weekends ago. It works perfectly. This is with different tire diameters (235/17 up front and 265/18 in the rear). I have an ABS defeat switch on the dash which cuts 12v power to the ABS computer if I need to defeat it for any reason (doing so will cause an ABS light on the dash but it goes away when you power it back on).

I mounted my G-force sensor under the dash, with the proper side up and proper end forward.

I replaced the twisted pair ABS wheel speed sensor wires with some shielded wire. I did it because I'm also using traction control and the wheel speed sensors were a bit noisy - though the ABS computer was just fine with them prior to my upgrading the wires.

I added two proportioning valves for the front brakes, one for front-left, one for front-right. When I adjust them, I just ensure I turn them the same amount. I haven't noticed a difference from all the way tight to 3 turns open, but I still need to play with them a bit.

My only brake issue, which is a major one, is that the pedal effort is WAY too high. I'm running 4 piston fronts and 2 piston rears off an 07 WRX, stock 1" master cylinder, and I did relocate the master cylinder pushrod hole up higher on the pedal per FFR instructions. But I have to stand on the pedal to get max braking and when doing that, I can't modulate. I basically have to go into a full ABS stop coming into each corner which is not good. I generally don't do that and opt instead to just brake earlier into a corner but I'm obviously giving up a lot of seconds on the track doing that. To try to fix this, I'm going to swap the 1" master cylinder for a 7/8" one, and move the hole in the brake pedal another 1/2" higher (thanks to another forum member who PM'd me suggesting that). I'm a little concerned about the angle of the master pushrod when moving the hole up another 1/2".... both the angle itself as well as the possibility of the pushrod hitting the master cylinder housing, but if that happens, I may physically relocate the master cylinder up higher on the firewall. That would be a real pain in the neck, because I wouldn't need to or be able to move it up much higher, which means the new mounting holes would be so close to the old ones that strength could be of concern, so I'd have to weld the old holes shut and grind it down smooth before drilling new holes. Hoping I don't have to do that.

[UnhipPopano]

"I added two proportioning valves for the front brakes, one for front-left, one for front-right. When I adjust them, I just ensure I turn them the same amount. "

When adjusting them you might turn the ABS off first so that it is not compensating and you can better detect when the wheels are locking up.


"My only brake issue, which is a major one, is that the pedal effort is WAY too high."

Have you tried changing the brake pads to a more aggressive material?

[Hindsight]

Thanks - I have tried the brakes with ABS off and on, and from a prop valve standpoint, it doesn't seem to make a difference.

I have changed the brake pads yes. Had new Hawk HPS or HPS+ (forget which) on there at first. Switched them to Ferrodo DS 2500 pads. Big improvement, but it improved it from totally unacceptable to just bad.

[JeromeS13]

I ran Hawk Blue pads for mine. They made a huge difference from the original Centric/Stoptech Posi-Quiet street pads. Felt fine with initial grab on the street and I had plenty of confidence in them on the track, as well.

[bbjones121]

Thought I would followup on this thread.

I tested my ABS system very well, and very often at the race track (Road Atlanta) two weekends ago. It works perfectly. This is with different tire diameters (235/17 up front and 265/18 in the rear). I have an ABS defeat switch on the dash which cuts 12v power to the ABS computer if I need to defeat it for any reason (doing so will cause an ABS light on the dash but it goes away when you power it back on).

I mounted my G-force sensor under the dash, with the proper side up and proper end forward.

I replaced the twisted pair ABS wheel speed sensor wires with some shielded wire. I did it because I'm also using traction control and the wheel speed sensors were a bit noisy - though the ABS computer was just fine with them prior to my upgrading the wires.

I added two proportioning valves for the front brakes, one for front-left, one for front-right. When I adjust them, I just ensure I turn them the same amount. I haven't noticed a difference from all the way tight to 3 turns open, but I still need to play with them a bit.

My only brake issue, which is a major one, is that the pedal effort is WAY too high. I'm running 4 piston fronts and 2 piston rears off an 07 WRX, stock 1" master cylinder, and I did relocate the master cylinder pushrod hole up higher on the pedal per FFR instructions. But I have to stand on the pedal to get max braking and when doing that, I can't modulate. I basically have to go into a full ABS stop coming into each corner which is not good. I generally don't do that and opt instead to just brake earlier into a corner but I'm obviously giving up a lot of seconds on the track doing that. To try to fix this, I'm going to swap the 1" master cylinder for a 7/8" one, and move the hole in the brake pedal another 1/2" higher (thanks to another forum member who PM'd me suggesting that). I'm a little concerned about the angle of the master pushrod when moving the hole up another 1/2".... both the angle itself as well as the possibility of the pushrod hitting the master cylinder housing, but if that happens, I may physically relocate the master cylinder up higher on the firewall. That would be a real pain in the neck, because I wouldn't need to or be able to move it up much higher, which means the new mounting holes would be so close to the old ones that strength could be of concern, so I'd have to weld the old holes shut and grind it down smooth before drilling new holes. Hoping I don't have to do that.

Thank you very much for the awesome follow-up.

[Hindsight]

You are welcome. I should add that the brake pedal effort issue, and proportion valve tuning should have nothing to do with the fact that I have ABS.... just to be clear.

[Bob_n_Cincy]

I added two proportioning valves for the front brakes, one for front-left, one for front-right. When I adjust them, I just ensure I turn them the same amount. I haven't noticed a difference from all the way tight to 3 turns open, but I still need to play with them a bit.

Hindsight.
Do you realize the you are just wasting force with the proportional valve. With it all the way tight you are reducing your front brake pressure by 57%.

Here are some rough numbers:
inputs:
100 lbs pedal force
0.78 sq-in master cylinder
1:4 ratio pedal.
front brakes 3.97 sq-in
rear brakes 1.76 sq-in
front PV =57%


calculated:
100 x 4 x .78 = 312 psi out of MC
front caliper squeeze force:
312 x 3.97 x.57 = 706 pounds
rear caliper squeeze force:
312 x 1.76 = 549 pounds
Total for all for wheels 2510

My car
100 x 4 x .78 = 312 psi out of MC
front caliper squeeze force:
312 x 3.97 = 1239 pounds
rear caliper squeeze force:
312 x 3.97 = 1239 pounds
Total for all four wheels 4956
I'm getting double your force with the same pedal pressure.
Bob

[Hindsight]

Hi Bob. I thought that when you TIGHTEN the valves (screw them in clockwise all the way), that this means you are allowing 100% of the pressure through them and when you loosen them all the way (counter clockwise), you are having them reduce pressure by 57% correct?

If my above statements are correct, I do know that the valve reduces pressure to the front brakes and increases pedal effort, however, there aren't any other options to adjust front to rear bias aside from changing to the Wilwood brake caliper + brake pedal setup, or doing what you did and adding larger rear calipers. The larger rear calipers while also keeping e-brakes is a really tough mod in my book.... one I may do some day but not just yet.

Right now I'm running the valves all the way tight, which I believe means letting all the pressure through, resulting in the front brakes doing more work, and all my pedal effort being realized to all the brakes. I still have a lot of pedal effort.

[Bob_n_Cincy]

Hi Bob. I thought that when you TIGHTEN the valves (screw them in clockwise all the way), that this means you are allowing 100% of the pressure through them and when you loosen them all the way (counter clockwise), you are having them reduce pressure by 57% correct?

If my above statements are correct, I do know that the valve reduces pressure to the front brakes and increases pedal effort, however, there aren't any other options to adjust front to rear bias aside from changing to the Wilwood brake caliper + brake pedal setup, or doing what you did and adding larger rear calipers. The larger rear calipers while also keeping e-brakes is a really tough mod in my book.... one I may do some day but not just yet.

Right now I'm running the valves all the way tight, which I believe means letting all the pressure through, resulting in the front brakes doing more work, and all my pedal effort being realized to all the brakes. I still have a lot of pedal effort.

My mistake Jeff,
Clockwise is full pressure.
When I ran my car with no PV and OEM caliber configuration. My fronts would lock up very easy.


There is another way that I was considering.

Using this device in the rear master cylinder line.
http://www.ecihotrodbrakes.com/brake_pressure_multiplier.html

in hindsight, this would have been cheaper.

Bob

[Hindsight]

Interesting option Bob, thank's for sharing that. I wonder if it would be compatible with an ABS system and if the devices are consistent enough to use two (one for each rear caliper), since that is what you'd need to do on an ABS setup.

[Bob_n_Cincy]

Interesting option Bob, thank's for sharing that. I wonder if it would be compatible with an ABS system and if the devices are consistent enough to use two (one for each rear caliper), since that is what you'd need to do on an ABS setup.

I forgot that you have a cross circuit with the ABS. If the system didn't have the yaw sensor, I suspect the you could just change plumbing and wiring to a front/rear circuit and get by with one BPM prior to the ABS unit.

I have ABS plumb in as a front/rear system. But never bothered to do the wiring. With your results, I might give it a try this winter.
Bob

[Hindsight]

It really works well Bob. Very smooth. The Subaru ABS doesn't beat on your brake pedal as hard or as on/off as some other cars I have driven.

I need to come up with a way to mount the same 4-piston front calipers I have, on to the back. Fabricating a bracket shouldn't be hard, but dealing with the backing plate and finding a rotor that is the right size for the caliper to allow full pad contact and also works with the drum parking brakes might be impossible. If anyone has a solution to this - I'd be interested in hearing.

[UnhipPopano]

In the brake threads there are a couple of threads that cover "finding a rotor that is the right size for the caliper to allow full pad contact and also works with the drum parking brakes ". For both using Subaru [Mounting front brakes in the back] and Wilwood, the off the shelf pads hang over the edge. There was also an explanation from Wilwood as to why the pads hang over the edge, and why it is alright.

[Hindsight]

Thanks! I will see if I can find those threads.

[grathke]

Hindsight, nice pics of the ABS lines.

Where is the brake fluid reservoir ?

[Rogier]

If you interrupt the ground wire of the abs module with a switch you don't get the lABS light when you disable the system;)

[Hindsight]

Hindsight, nice pics of the ABS lines.

Where is the brake fluid reservoir ?

I bought Mike's (Replica Parts) remote reservoir and mounted it on the windshield cowl.