Nissan 370Z Forum - Braking problem

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Nissan 370Z Forum (http://www.the370z.com/)

- Brakes & Suspension (http://www.the370z.com/brakes-suspension/)

- - Braking problem - malfunctioning ABS (http://www.the370z.com/brakes-suspension/3916-braking-problem-malfunctioning-abs.html)

SoCal 370Z

03-14-2010 12:01 AM

You've gone so hardcore that Nissan should just retain you as a consultant and use you for Z product development.

B1nks

03-14-2010 06:50 AM

Quote:

Originally Posted by travisjb (Post 444488)

I'm going to revive this old thread... new information

So, despite adding a massive AP Racing BBK and taking hundreds of pounds of my car, I'm still getting the icing issue on occasion. Happened to me today at Firebird Intl Raceway. I was going towards a carousel and braking hard to get set up at the correct speed and on the right line. I had just passed another car and had to make a big transition that upset the car's balance... then bam - icing set in and I began a slow terrible grinding towards the outer part of the track and straight-line braked (but not nearly as fast as I would have liked!)... nearly ended up 4x4'ing. It was total ABS lock up, but as has been previously described it was v inefficient with slow pulsing like riding on ice.

It didn't happen for the rest of the day.

It was NOT an overheat issue b/c it was early during a session.

As it turns out, there was a fellow at the track today who happens to be a test driver for a certain car mfgr that we know and love. Please don't ask me to elaborate. He says that the 370z and the 350z before it have had this issue. What happens has nothing to do with overheating. The ABS computer is kicking in icing mode when it senses any one wheel turning at a substantially different rate than the others. Confirmed it is a different mode than normal ABS when limits are exceeded.

We discussed potential solutions. His belief is that there is NOTHING that can be done except to get an increasingly stiff suspension that is less likely to result in 1-wheel up or other conditions that allow wheels to spin at differing rates.

Not sure where to go from here, but figured I'd share these thoughts.

So, anyone else have 'ice mode' recently? Anyone thinking about how to fix?

That's very interesting and yet not very surprising when I stop to think about it. Actually I think we've all suspected it had something to do with the ABS programming. Why doesn't every vehicle have this problem though ? I would figure that every vehicle had the same ABS standard programming. Also could it be as easy as fix as a reflash ?

ChrisSlicks

03-14-2010 08:21 AM

Quote:

Originally Posted by B1nks (Post 444670)

All vehicles do have the problem, it's just a matter if you have reproduced the circumstances to induce it. We got excited when we noticed the stock pads were so bad but I knew something else was still going on.

I totally agree with the diagnosis by Travis at this point as those are similar circumstances to where I've encountered the ice mode myself. The two major times I have encountered it was hitting the brakes after going over a sharp crest, and after hitting a crack in the pavement. Prior to that I had pad fade which was confusing the diagnosis.

travisjb

03-14-2010 09:39 AM

so now that we have the diagnosis... what do we do about it? ideas:

1. as binks points out, maybe there is some way to change the ABS computer to either get rid of the mode all together or 'widen the parameters' that cause this mode to kick in... I would have no idea where to start with this solution

2. fool the sensors into recording less wheel spin value difference... this is playing with fire, could cause more probs than it solves

3. disable ABS all together... again, not good for all but the most hardcore... I wouldn't do this

4. *much* stiffer suspension... band aid... prob requires 800 lb/in springs

others ?

ChrisSlicks

03-14-2010 10:38 AM

Quote:

Originally Posted by travisjb (Post 444738)

1. as binks points out, maybe there is some way to change the ABS computer to either get rid of the mode all together or 'widen the parameters' that cause this mode to kick in... I would have no idea where to start with this solution

Stillen might have to use their Nissan contacts for this one. There might be a race program or alternate ABS computer.

Quote:

2. fool the sensors into recording less wheel spin value difference... this is playing with fire, could cause more probs than it solves

Possible, but would require an inline computer to receive the values, translate and retransmit to the ABS computer.

Quote:

3. disable ABS all together... again, not good for all but the most hardcore... I wouldn't do this

Actually probably the best solution for now but is going to require us to learn proper threshold braking techniques.

Quote:

4. *much* stiffer suspension... band aid... prob requires 800 lb/in springs

Also has the detriment of possibly reducing corner grip if taken too far.

travisjb

03-14-2010 09:20 PM

Here's another idea... softer anti-sway bars! Very stiff anti-sway bars are going to cause the inside wheel to lift and 'overspin'. When this happens on the rear axle WHILE BRAKING, that's precisely when our problem seems to occur. Compounded by the fact that the rear end is light... Inside rear corner picks up, inside wheel spins faster than outside, ABS reacts to the extreme wheel speed difference by assuming the car is spinning on ice and it uses a VERY AGGRESSIVE slow speed ABS that is locked in until the car reaches nearly a complete stop.

So now I'm contemplating using the softest setting on the rear sway. It will cause more understeer, which I will have to manage some other way. Like perhaps with a square tire setup (275 widths all the way around).

Just a working theory.

I'm very curious to know if anyone has had this problem with the stock sway bars. I'll have to go back and check notes from early last year before I got my sways.

LateralG'z

03-14-2010 09:37 PM

I second this!:iagree:

Quote:

Originally Posted by SoCal 370Z (Post 444538)

You've gone so hardcore that Nissan should just retain you as a consultant and use you for Z product development.

spearfish25

03-14-2010 09:59 PM

Quote:

Originally Posted by travisjb (Post 445895)

I'm very curious to know if anyone has had this problem with the stock sway bars. I'll have to go back and check notes from early last year before I got my sways.

This is probably why C&D introduced their Nismo to a concrete wall...

I have a fully stock suspension and have upgraded my brakes with Motul RBF600 fluid and Carbotech XP10/8 pads. I'll be at Gingerman in three weeks and will report back if I get ice'd. Haven't had it happen before though, even on a wet track with stock pads and fluid (not that pads and fluid really have anything to do with it).

Personally, I'd be happy to kill my ABS and threshold brake. I find it very intuitive and would be a nice flashback to driving my landrover defender in the snow.

travisjb

03-15-2010 12:12 AM

Had forgotten about the C&D incident until you mentioned it... you must be right - ABS icing.

If there had been a wall nearby yesterday my car would have been toast. If I remember correctly, the car resisted my steering inputs when it went into icing mode, which made the whole process tremendously difficult and frankly dangerous. I wonder if Nissan intended for the car to stop responding to driver steering inputs in this mode? If they did so deliberately, I think they have a serious liability that will eventually catch up with them and unfortunately some poor driver(s).

Re threshold braking, it is only a solution for a select few drivers. I've driven karts and formula cars like this but for a TT car that I'm pushing to the absolute limit, I like the idea of having ABS to fall back upon. I'd much prefer a real fix to this issue vs disabling.

Quote:

Originally Posted by spearfish25 (Post 446003)

Josh@STILLEN

03-15-2010 12:18 AM

Heavily following this, and bringing it up the ladder tomorrow.. as we also plan on heavily tracking our S/C'd 370Z, and will undoubtedly run into this as well.

Thanks for the collaboration of information, and I will happily post our findings as we get with Nissan and lean on our resources as well.

You guys are awesome in your documentation, and a complete benefit to this community.. repping like crazy on this thread..

travisjb

03-15-2010 12:38 AM

Thanks, Josh. Appreciate Stillen getting involved with the diagnosis and hopefully someday a solution. You guys are uniquely positioned to address this one, given your brakes expertise, knowledge of the ECU, relationship with Nissan, and the fact that you have skin in the game with your own car!

spearfish25

03-15-2010 06:21 AM

Quote:

Originally Posted by Josh@STILLEN (Post 446230)

Great to have you guys on board with this as well. Just keeps reinforcing why I like Stillen so much.

ChrisSlicks

03-15-2010 08:22 AM

Travis, you say you lost steering input as well. Do you attest that to the slow cycle time of the ABS in "ice mode" or is there a remote possibility that you could have run over something slippery given that you were braking off-line?

travisjb

03-15-2010 10:56 AM

Quote:

Originally Posted by ChrisSlicks (Post 446475)

Can't stress enough that it was an ABS issue... def not a track condition... the loss of steering has something to do with the fact that my power steering is only partially working right now so it takes a lot of force to begin with, i'm running 275 series r-comps on the front which don't turn in easily, and abs tends to strtn car out when stopping... all factors together made it harder to muscle the steering wheel

ChrisSlicks

03-15-2010 12:24 PM

Quote:

Originally Posted by travisjb (Post 446633)

Gotcha. Was trying to figure out if you were saying that you were turning the wheel and nothing was happening or it was just really hard to turn the wheel. Now I see it was the latter.

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