Ice mode solution?

AutoX Z

I ran with the ABS disable once because of a faulty brake solenoid that told the abs computer that the brakes were always on and therefore wouldn't allow full throttle. Pulling the brake-light fuse tricked the ECU into allowing full throttle but disabled the ABS in the process. It wasn't that hard to modulate the brakes even with Hoosiers on the car.

Now that you mention it though the one time I saw my codriver lock up the brakes during that event it was the inside rear tire, not the inside front that you would expect.

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pyrrhus17

so so far no ice mode solution ? really makes me wish i'd bought a different car to do track days with. Being a noob and all just a little scary .
dont know if this helps http://www.lotustalk.com/forums/f100...-solved-36810/
or this http://forums.rennlist.com/rennforum...ly-got-me.html and
http://forums.corvetteforum.com/auto...ere-a-fix.html

cossie1600

Not the same problem as the Lotus, more like the problem with the Corvette.

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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travisjb

I just spoke with Bosch and with the head of their major west coast distributor

Not going to quote anyone directly but basically the theories discussed in this thread are correct. The DOT approved versions of Bosch ABS induce ice mode when the wheel rate sensors detect variation across the four sensors. I am not clear if it is front/rear overall or any one wheel or both, nor did I find out what % difference the computer looks for nor timing involved in the algorithms... but it is a safety mode designed to help in the majority of street situations... hard to blame them for that

There are two systems available for dedicated track vehicles. One produced by Bosch and one produced by Continental. These systems are only provided for vehicles not used on public roads and purchasers are required to sign a waiver that is kept on file with the mfgr. The systems are sold through distributors. The Continental system is apparently a modified BMW ABS that is not configurable. The Bosch system is a bottoms-up race ABS with config options. Bosch has two major US distributors, one east coast and one west coast. The west coast distributor is Brian Sekata with MS Electronics.

I realize this is not all that helpful for those of you that will keep your cars street legal. Sorry, I have nothing to offer you folks. The only possibility I can think of is to find someone that can crack the computer and re-write the code... but then there is an issue of liability and intellectual property

For anyone reading this that has a dedicated track Z (either 370 or 350), it may be possible for us to work out a group buy on Bosch Motorsports ABS systems. I have no commitment from Brian or from Bosch, but they are interested in starting the conversation with us and asked me to carry the idea forward. If there are enough of us willing to sign that waiver, there might be a break off the system price... as many of you know, it is $10K today ... but what if it were $6K ??? better braking performance and safe guard against ending up in a concrete wall... the system is also highly configurable - from the cockpit you can adjust proportioning and how the ABS reacts

In any event, please spread the word if you know anyone else with a dedicated track Z

Thoughts?

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Shamu

I think the Grand Am team found a differnt motorsports abs solution for around $7K. I can ask but they indicated it was one of the best race oreinted abs systems they have ever used.

The problem using the stock system on our cars on the track is that they have terrible rear brake bias. Just disable your abs and stopm on brakes and you'll understand issue that our system is dealing with when we get good pads and bigger tires on the front.

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Grant

gomer_110

Not too sound like a noob but if the source of the problem is poor factory brake bias front to rear then wouldn't the simple and cost effective solution be to add a brake bias proportioning valve to the car. Yeah it might take a little trial and error to dial in but I would guess a hell of a lot cheaper than one of these ABS systems.

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ChrisSlicks

If you did an ABS delete then that would be the best solution, but not sure how well that would work in conjunction with ABS.

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Shamu

That or smaller 350Z Bermbo caliper and rotor

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Grant