Ice mode solution?

travisjb

^ I did the same... BC Racing are just fine, but not JRZ's... or Penske... etc

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wstar

Well I got to think on (and play with) this all day, and I think my initial reaction to "oh no I have to deal with ice mode" was overreaction. There's a few layers of analysis here, not sure what order to put it all in, and I'm trying to avoid my tendency to get really long-winded . But the bottom line in my case I think is:

An additional major contributing factor was front pad fade on the XP8s, even on my street tires. When the fronts start fading, of course the bias goes to the rear, which helps kick on the ice-mode.

Based on that alone, it would seem like it would be best to up the fronts to XP10 (at least) and get my brake ducts finished, which should lessen both the fade and bias contributing issues.

But, a major contributing factor to the pad fade (well, aside from lack of ducts) was that I was carrying around a lot more speed due to some skills improving, but I was abusing the brakes way more than I should have had to. We corrected some of this today, and I was able to make even faster lines with less brake abuse, and it helped a lot. I still got some ice-mode late in a hot session, but I was able to modulate through it and come out ok, and after pushing through that barrier for a bit, the XP8 front pad fade of course starting becoming increasingly obvious.

So really, learning to use the threshold better (so I'm not dipping into ABS in the first place), and not abuse my brakes in ways that aren't even warranted will go a long way towards fixing this for me on a practical level, although the ducts certainly can't hurt as well. Even then, I'm still going to be pushing the limits of the XP8's on street tires, but I think trying to upgrade the pads too far against these tires is probably a bad idea (just going to be a lot more touchy and sensitive on the ice-mode line when it does hit it), and I also think I haven't learned enough of the limits of these tires to consider upgrading to slicks either.

Really, where that leaves me for reducing the overheating problem is I need to not go balls out on the straights. If I held back at say 70% throttle on those long straights instead of flooring it, I wouldn't have as much speed to shed, and the braking system and the tires would all line up with my driving skill in the corners and work properly. In other words, even my lowly NA V6 really has a little too much power on tap for an ideal learning environment at my level of skill, if I want the rest of the system to hold up to a long session.

One way or another, I can play with modulating through the fade + ice mode and/or reducing my straight speeds and mitigate the ice-mode while continuing to learn how to push these tires to their fullest, and then consider further true tire+brake upgrades later when I'm ready, I think. The ducts will go on ASAP though

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AutoX Z

I run completely OEM brakes and get engage ice-mode at will. I've learned to drive around it and it is rarely a problem anymore.

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ChrisSlicks

I had it on the OEM setup at auto-x as well. It would only present itself towards the end of the session when things were warmed up. Everything in auto-x is much more deliberate and sudden that I think it was just easy to catch the ABS system off balance. When I went smoother on the brake pedal it was avoidable in this case.

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clintfocus

well im going to buttonwillow sunday, stock suspension and wheels with RE11 street tires. I got DTC 60s for the front, was going to run the OEM pads in the rear. ill let you guys know how it goes

bullitt5897

What I found that was causing the ice mode was that the rear brakes were stopping the rear wheels/tires faster than the front. Because of that the car would release the brakes causing the "ice mode". This was from my brake test last year. I mean we tried everything from pulsing the brakes to me standing in the car on the mothers. Once the rear tires locked up or got really close to lock up "Ice Mode" came into affect. I think because of the bias in braking power from front to rear it causes this affect. we tried it on a stock car with upgraded pads and lines and my car with the alliance BBK. The BBK under the right circumstances was able to trigger it alot easier since we were running bigger rotors and calipers in the rear... This also depended on the ground composition as well... if it was dirty and sandy it happened a lot faster. If it was clean it didnt happen at all on the bbk and stock. With all the weight shifting forward under hard braking the rear end has less friction from the ground under braking thus allowing less effort to stop the rear wheels and causing Ice Mode...

My hypothesis on the solution is to run a stiffer front than rear bias and to run less aggressive pads for the rear.

Mike

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bullitt5897

Ohh and DO NOT DISABLE YOUR "ABS OR ABS MODULE" you will lock all four wheels up in an instant even at slow speeds like 35mph!!! Trust me I ruined a set of $1200 tires testing that theory out. The car went immediately sideways. I tried a modular increase in brake pressure and lock up. I also tried pulsing and with each pulse the wheels locked up. It is almost like an instant on/off switch with the abs disabled...

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wstar

Yeah, I meant to mention that in my above post. When I mentioned the idea of disabling ABS to a few others at the track event, the advice I got back was "Yeah that's great, except one little screw-up and you'll flat spot and ruin a tire, better to have the ABS as a backup at that point and not ruin tires."

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travisjb

You know what... I agree that it is "easy" to lock up and flat spot w/o ABS on... but that's the best training in the world and your ABS is only masking the situation... I was able to improve my setup a lot w/o ABS and then turned ABS back on, making the whole thing much smoother under braking

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wstar

Yeah but what's the practical difference between saying to yourself, "Oh I screwed up and managed to engage ABS" when you feel the pulsing, and saying to yourself, "Oh I just screwed up and now I need an expensive new tire?". Well, aside from the $$$

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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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