My vote for the worst ABS system goes to?

[CSG Mike]

Originally Posted by Element Tuning

Mike, DTC70 front and XP12 rear

Ah, the DTC70's torque ramps MUCH quicker with pedal pressure than the XP12. Also, the DTC conducts heat through the pad, whereas the Carbotech tends to hold it on the surface. Third, the Carbotech is a compressible pad, whereas the DTC is not.

I'd make an educated guess that the DTC's larger bite caused it to heat up faster relative to the rear, further increasing front brake bias, causing the fronts to be functioning far more than the rear.

Can you do like 2-3 80-20 stops, and then run out of the car and take laser temps of the brake rotors? I'd bet the fronts will be a lot hotter than the rears. We try to keep the temperatures approximately equal between the axles to maintain brake balance.

Try square compounds or similar staggered compounds...

[Calum]

Originally Posted by Element Tuning

It's definitely "normal" to need more rear brake force when increasing rear downforce and also increased suspension stiffness for optimal braking. Think of it like if you put a 355mm front brake kit on, you better also put close to a 355mm rear brake kit on if you have a "Pro" level car otherwise you're giving up to much in the rear.

Now my car isn't hugely different than it was a couple seasons ago in terms of downforce.

Having more rear downforce etc. shouldn't cause the ABS to stop working. As Jeremy Clarkson would say, "it's stupid, stupid, stupid" LOL!

Yeah I only wrote half of that thought. I was wondering about the bias not the ice mode. Ice mode sounds terrifying.

[DougW]

The lng and lat sensors are in the ABS pump under the hood you might try mounting the pump in rubber to slow down the noise from the higher spring rate or take out every other tooth on the ABS rings to slow the speed rate but either way you need to log it to see why then you can fix what.
DougW

[Element Tuning]

Mike, I agree but really given I've gone back to oem brakes it shouldn't cause an ABS shutdown.

Doug, we do know from our previous wheel speed data it's all over the place but what we don't know is like you said, how is the oem system dealing with the noise.

My brakes used to be very good, let's remember this. I have a suspicion my problems and others could be related to yaw/pitch and pedal pressure and how the ABS system uses this data. With race pads and or larger rotors you end up with more brake torque so less pedal pressure is needed. Now you add into the mix stiffer suspension and more rear aero and all of a sudden you have less brake dive/pitch. I could totally see how that data could be used by the ABS to think the car is on ice because there is little pedal pressure, there is no pitch, front ABS cycles, and voila "ICE Mode!"

I think the brakes are mechanically way too biased to the front. Turn off your ABS and you'll know what I mean! I've already sacrificed $2k in tires so I really am not looking forward to figuring this out but I'm goimg to plumb in the driver adjustable bias valves to reduce front brake force. If it balances the brakes we should be able to figure out what front brake piston diameter will help.

Like Mike said you can to some degree balance the brakes with pad compounds and I do run more friction in the rear of our STi vs the front but temperature imbalance can be tricky.

[DougW]

I'm not sure why your wheel speeds are all over the place mine have always been very consistent when logging them off CAN. The ABS can't work if the wheel speed is erratic that is it's first input then pressure then G slip/rates. Anybody every looked at hacking the stock ABS?
DougW

[Element Tuning]

I'm talking about the raw data and not what you would see via your CAN data logger.

[Dave-ROR]

I actually haven't experienced ICE mode on track yet, but since I don't use the BRZ for competition I've already left that extra margin just in case.


The ABS system is this car isn't even as good as the system Honda put in the ITR though 15 years earlier.

[EAGLE5]

A data point that might be useful... pfc 08 in the front and dtc 60 in the rear gave definite rear bias to the brakes. Not fun. It did seem to get worse as the sessions each wore on.

[Element Tuning]

Originally Posted by jsimon7777

A data point that might be useful... pfc 08 in the front and dtc 60 in the rear gave definite rear bias to the brakes. Not fun. It did seem to get worse as the sessions each wore on.

And as a result what was happening? ABS fail, tail happy, ABS rear?

[EAGLE5]

Originally Posted by Element Tuning

And as a result what was happening? ABS fail, tail happy, ABS rear?

Rear would slow more than the front and start dancing a little when threshhold or abs braking from 100 plus. The abs definitely came on in the rear first. I don't remember it ever engaging in the front. It seemed fine on slower corners. I'm not fast. Switching to stock pads eliminated the dancing but the bite is weak. I have not been back to the track yet to try pfc 08 all around. I have a mostly stock car and never exceeded 114. Definite oh shit moments with the rear dancing. Made me slow down a lot on straights.

[Element Tuning]

Ok thanks. Typically I'm having this issue when speeds are in excess of 140 mph. Ya know when you need your brakes the most Toytoa/Subaru! LOL!

Maybe my XP12 are glazed over in the rear? I'm going to put all OEM pads on and the Prius tires for testing. LOL!

[Calum]

Originally Posted by Element Tuning

Ok thanks. Typically I'm having this issue when speeds are in excess of 140 mph. Ya know when you need your brakes the most Toytoa/Subaru! LOL!

Maybe my XP12 are glazed over in the rear? I'm going to put all OEM pads on and the Prius tires for testing. LOL!

The comedic effect of that much power and down force on those stock tires will make video an absolute requirement for that test session.

[DougW]

Originally Posted by Element Tuning

I'm talking about the raw data and not what you would see via your CAN data logger.

How are you reading it then, I pull it off the high speed CAN not the OBD2 port.
DougW

[Element Tuning]

Originally Posted by DougW

How are you reading it then, I pull it off the high speed CAN not the OBD2 port.
DougW

These were OEM reverse engineering tools/scopes/sniffers....Pico? We needed the data for the traction control in the Hydra EMS. The CAN computer is like any other and it reports the data in a readable frequency and is typically averaged. We had to do exactly the same.

What we would like to know is "why" it does what it does under racing conditions. What is the trigger for ice mode or ABS shut down? It's all temporary and will reset immediately ornin case of the ABS just a key cycle. Even if we just knew the basic logic it would help without h a work around.

I just think the brake force distribution computing is too slow to deal with the fixed mechanical front bias inside the pump module.