Rock Hard Brake pedal in the middle of an autocross run...

[Dezoris]

Originally Posted by CSG Mike

I'm assuming you're lifting a rear?

We have VSC kick in with a 5 second hold on bad surfaces under throttle, but I haven't needed to brake on that type of surface.

Do you or anyone else have datalogs showing wheel speeds?

See: http://www.ft86club.com/forums/showthread.php?t=68310

Here is the area where I had big troubles with ice mode. I don't have the video of plowing through cones but thats where it would happen. I had to start braking way earlier or go off line to stop it.

[ame="https://www.youtube.com/watch?v=pgU6BIWjcG0"]Ice Mode - YouTube[/ame]

I don't usually log wheel speed sensors. I always have TQ running and logging but I don't think that's very easy to pull data from?

Probably should get AIM.

[ddeflyer]

Originally Posted by stugray

I am amazed that noone on this thread has asked what "IT" IS....

If you attempt to use the brakes and they are "hard" and depressing the pedal does nothing, what state could the brake system be in?

The only way I can imagine the pedal being harder than usual is if the VSC (or BFD) is active and trying to APPLY the brakes itself.
If the ABS is activated, then the only thing the user should notice is a spongy or pulsating pedal. Not a rock hard one.

So what situations can the system apply the brakes and make the pedal feel hard?
As stated above: A rear wheel lifts causing the electronic diff to kick in and try to apply brakes to the wheel that is lifted (spinning).

Is our system a dual "Inline" master cylinder where a single rod moves and applies pressure to front & rear piston circuits?
Or is our system more like the tilton dual master cylinder system where if one cylinder stops moving and you apply more pressure, the other MC moves and applies pressure to the other circuit?

I think understanding how the system works and what could make it act this way is key to getting to the root of the problem.

And that Smart Stop Technology crap doesnt sound right.
If SSTI was stepping in, I dont think I could heel toe during a downshift

I would imagine that the hard pedal might come from the system preventing the pressure from reaching brakes. I don't know where the EBD system is located, but if it is on the hard lines and it was preventing brake pressure then you would get an astoundingly hard pedal.

Automatic activation of the brakes (applying pressure) should make the pedal pulse or even go down further.

[qoncept]

Wow, I've never had this happen (CSR BRZ on 245 Z214s) in probably 250 runs across ~10 different sites and I never do the pedal dance.

[stugray]

Originally Posted by ddeflyer

I would imagine that the hard pedal might come from the system preventing the pressure from reaching brakes. I don't know where the EBD system is located, but if it is on the hard lines and it was preventing brake pressure then you would get an astoundingly hard pedal.

Automatic activation of the brakes (applying pressure) should make the pedal pulse or even go down further.

I think this is where some of the confusion is coming from.

The ABS system can only release the brakes it cannot apply them.
Although is IS in charge of repressurizing the system AFTER it releases them (keeps them pumped up for you)
This is the pulsing most of us are familiar with with "older" ABS systems.

The VSC and electronic DIFF can apply the brakes to individual wheels.

The BFD can only relieve pressure to front/rear (that is my understanding, and likely incorrect)

[ddeflyer]

Originally Posted by stugray

I think this is where some of the confusion is coming from.

The ABS system can only release the brakes it cannot apply them.
Although is IS in charge of repressurizing the system AFTER it releases them (keeps them pumped up for you)
This is the pulsing most of us are familiar with with "older" ABS systems.

The VSC and electronic DIFF can apply the brakes to individual wheels.

The BFD can only relieve pressure to front/rear (that is my understanding, and likely incorrect)

As I understand it, these systems are all essentially one. The car has a body control computer which, among other things, controls VSC, EBD, ABS, traction control, braking for the diff's functionality when one wheel lifts, etc.

Given this, I think it is likely (from a logical perspective, I have no real proof) that the body control computer would be able to apply, relieve, block, and modulate the brake strength to each wheel.

[stugray]

Originally Posted by ddeflyer

Given this, I think it is likely (from a logical perspective, I have no real proof) that the body control computer would be able to apply, relieve, block, and modulate the brake strength to each wheel.

I agree. That is why it is imperative for us to not mix up the terms TC, ABS, VSC, BFD, etc.

They are all one system, so when we say things like "disables everything, but leaves ABS still active" it is difficult to know what that means.

If the pedal dance disables TC & VSC as most believe, but leaves ABS still active, WHICH parts of each of those are enabled/disabled??

I am even curious "Does the main ECU control the TC & VSC systems, or are those functions in a separate computer?"
My guess is that the key ABS functions work without intervention from the car's main ECU.
But I bet the VSC, TC, etc IS controlled by the ECU and can probably issue commands to the ABS when in TC/VSC mode.

Is there an ABS computer in the engine bay with CAN Bus run to it?


Sorry for thread jack.

[ddeflyer]

Originally Posted by stugray

I agree. That is why it is imperative for us to not mix up the terms TC, ABS, VSC, BFD, etc.

They are all one system, so when we say things like "disables everything, but leaves ABS still active" it is difficult to know what that means.

If the pedal dance disables TC & VSC as most believe, but leaves ABS still active, WHICH parts of each of those are enabled/disabled??

I am even curious "Does the main ECU control the TC & VSC systems, or are those functions in a separate computer?"
My guess is that the key ABS functions work without intervention from the car's main ECU.
But I bet the VSC, TC, etc IS controlled by the ECU and can probably issue commands to the ABS when in TC/VSC mode.

Is there an ABS computer in the engine bay with CAN Bus run to it?


Sorry for thread jack.

I *think* all of those are managed/controlled by the body control computer and are generally independent of the ECU. The body control computer is a separate module; there is a permanent OBDII code for the ECU and body control loosing sync on the CAN bus.

[CSG Mike]

Originally Posted by Dezoris

Here is the area where I had big troubles with ice mode. I don't have the video of plowing through cones but thats where it would happen. I had to start braking way earlier or go off line to stop it.

I don't usually log wheel speed sensors. I always have TQ running and logging but I don't think that's very easy to pull data from?

Probably should get AIM.

Try reducing your damper settings by 1 or 2 clicks...

[Simmons]

I get ice mode every time I AutoX.


The only way I can try to prevent it is to let off the gas,......wait.....then brake.


I left foot brake, and my co-driver doesn't. He Only had it happen once.


I really wish there was a way to fix it.




Simmons

[rx3]

This problem has meanwhile started to occur more often since I started to run on slicks.

Besides the pedal dance is there any solution to this problem?

[CSG Mike]

Originally Posted by rx3

This problem has meanwhile started to occur more often since I started to run on slicks.

Besides the pedal dance is there any solution to this problem?

Stop stabbing at the brake pedal, and focus on being smooth.

[rx3]

It only happened on bumpy sections (I already knew that braking in turns can provoke a hard pedal). (So it's not necessarily me who's lacking smoothness.)

But after some searching I think one would need some sort of a motorsport ABS to prevent this. So there's nothing one can do about this other than just quickly release the pedal and brake again (regardless of what trees might coming closer rapidly).

[Element Tuning]

I haven't had ICE mode since switching up to a brake system RR Racing designed for us to shift more mechanical brake torque rearward. I still get ABS failure when I push 10/10th and I can't seem to get the pedal dance to work. My radiator is probably too good to get up to temp in the pits but I tried it after my race and still failed. The car is now raceable even without ABS due to the brakes but I still can't brake as hard as I need to (engage abs and back off).

I'm going to tweak my suspension setup slightly to try and make the system happier. I discovered the fault is more likely "stability control" as the light popped on twice during my warm up laps when I wasn't braking hard.

Anyways for ICE mode to recover you have to get off the brake and then back on for the brake pressure to return. The Nissan Z race guys have this same issue and that can keep you out of the tire wall.

[renfield90]

Originally Posted by Element Tuning

I haven't had ICE mode since switching up to a brake system RR Racing designed for us to shift more mechanical brake torque rearward. I still get ABS failure when I push 10/10th and I can't seem to get the pedal dance to work. My radiator is probably too good to get up to temp in the pits but I tried it after my race and still failed. The car is now raceable even without ABS due to the brakes but I still can't brake as hard as I need to (engage abs and back off).

I'm going to tweak my suspension setup slightly to try and make the system happier. I discovered the fault is more likely "stability control" as the light popped on twice during my warm up laps when I wasn't braking hard.

Anyways for ICE mode to recover you have to get off the brake and then back on for the brake pressure to return. The Nissan Z race guys have this same issue and that can keep you out of the tire wall.

Unplugging the steering angle sensor (underneath the steering column plastics) will disable all stability functions.