Ice mode solution?

wstar

Hmm yeah the Corvette issue is obviously related. These posts in particular are interesting:

Corvette Forum - View Single Post - ICE MOde ! ... off track event is there a fix ?

Corvette Forum - View Single Post - ICE MOde ! ... off track event is there a fix ?

They seem to be focusing in the other direction (increase rear bite to lessen the problem), but that's probably just differences in the overall setup and use of the vette versus ours, and/or some minor revision to ice-mode programming in some shared ABS controller code.

I think the bottom line for both cars is roughly what that second link talks about though: if one or two wheels wheel decelerate/lock *much* faster than the others (and probably if all 4 decel/lock much faster than should be possible on a grippy surface), the car assumes it's on ice and limits overall braking force heavily. When you think about it, with all four wheels firmly planted to the pavement the wheels should be decelerating evenly. Their (the ABS programmers') logic almost makes sense, except they're not accounting for the possibility very uneven dynamic corner weight loading, and they're not accounting for the possibility of a bumpy but otherwise grippy surface (esp combined with harder suspension setup).

Stabbing exacerbates this, and it makes sense to me that higher rear bias (due to grabby rear pads, due to front fade, etc) would exacerbate it in many common scenarios, since the initial stab will unload weight from the rear wheels, allowing them to lock up quickly under reduced weight with a hard-biting pad. Having wheels unloaded due to bumpy pavement, suspension setup, and brake timing relative to all of that would exacerbate it as well.

And really, I'm not buying the idea that this is a good tradeoff on the street, either. It might be a good tradeoff for Nissan and Bosch's wallets from a lawyer perspective when running some statistics on which scenario results in more total lawsuit damages, but even a consumer street driver shouldn't have to take the tradeoff of "ABS might totally screw me if the pavement is too bumpy or I was cornering hard when I first hit the pedal" just to get it to work right in icy conditions.

I guess they figure in those scenarios anyone driving fast enough on bumps to feel them hard, or anyone braking while still under dynamic loading from a hard corner, could probably be written off as "it's your own fault you wrecked, you weren't driving safely on the street to begin with"? Their code works great for probably the two most common ABS lawsuit cases for them: straight line stabbing-the-brakes stop in commuter traffic way too late because the driver wasn't paying enough attention, either dry or in slippery conditions.

EDIT: I wonder if it would be possible for someone to dig up a Bosch (or other ABS mfg) engineer to discuss this on the side and confirm exactly what the behavior is and why?

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ChrisSlicks

I don't think the car ever determines it is on ice, however the controller does have a wide traction range (too wide IMO). The fastest way to stop on ice and gravel is full lock up, ABS can extend stopping distances by 2x to 3x if improperly applied (not allowing enough lock between releases).

I think it is a flawed design, but you are probably right that it goes back to liability. If it was a true 4-channel ABS controller then it can individually give full stopping potential to each corner. However doing that could cause the car to pull in one direction or the other so they create artificial limits on how much the bias can be left to right, front to rear. Given the large rear brakes, their maximum limit may not be enough in the extreme cases especially front to rear.

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cossie1600

I have owned all the cars you mentoned. C6, 370, 350, elise. The problem is notiable on the 370 and c6, not so much on tje 350 or elise. while most believe the problem is likely due to the brake bias and abs on the 370, I personally dont believe they are the main reasons, definitrly a factor. Here is why

1. The 350 non brembo had way more rear brake bias than the 370, yet ice mode isnt quite as bad.

2. The corvette has way more front bias, the problem is as bad as the 370.

personally here are a few things I have learned on the 370

Almost all the ice mode occurance happened on bumpy area or low grip surfaces.

I have three set of pads and I have mix and match with different combo. Running oem fronts and xp10 didnt throw the car into ice mode frenzy and my datalogger showed a slightly better stopping distance. Thats why I still believe the brakes have too much front bite and it is flipping the system out. With all that said, I feel like the giant brakea and aggressive nature on race pads are locking the front wheels too easily and quickly, causing the ice mode. Of course that's just my opinion and I could be way wrong on it. It's just some of the things you guys are experiencing are different than mine. Btw I ran the 350 with the same pads and never really experiences ice mode. I am curious if nissan patched the abs software or maybe the little calipers I had didnt have the stopping power like my 370s akebono?

Sry typing on a phone

Shamu

I challenge you to unhook abs and see if you think its front bias. I dont see it. Niether did the Grand Am team. Its heavy rear bias. Most of us are dragging rears and system is releasing things to keep the car from spinning.

I originally thought it was front bias until I unhooked abs and tested the car with fast stabs and threshold braking on the track. And I have huge clampers in the front. Its lighter rear end with pretty aggressive rotors and calipers that cause rear to lock up from what I see.

Grant Am guys are pretty sure most of issues will go away with rear caliper change but I havent had a chance to make the change yet. Also have been waiting to see if there are any other solutions before I commit.

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ChrisSlicks

That is one of the most common triggers, pad fade is the other time I have experienced it but it feels slightly different in the way that it recovers.

Yes, I had the G35 with the crappy calipers like your 350 and never ever had a problem despite getting the brakes to the point of smoking. People were impressed with the stopping power. Did any 350 owners with the fixed caliper Brembo's experience ice-mode? I'm not sure if we can use their ABS controller however thanks to the newer sensors (yaw etc) and if it would be compatible with the ECU.

My brake pad experiments in the 370 have had the opposite results to yours though. I tried running the same compound front and rear for a session and it was pretty difficult. Minor ice-mode every time you stepped on the brake too hard too quickly. With a lesser pad in the rear it doesn't happen as much. Basically the same problem as the Corvette just in reverse.

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Shamu

How about this?

Turner Motorsport | Racing ABS Wiring Harness

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Grant

travisjb

Interesting... on the site it says the controller is an extra $6K, however, so likely it ends up being $10K as well

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Shamu

I wrote them. They indicated harness works with e46 m3 that uses same bosch system so if you could find an m3 parts car you could pull system but what is likelihood of this.

I think ATE system is what grand am team used. So I wonder if ate makes full system?

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Grant