Braking problem - malfunctioning ABS

travisjb

a nissan test engineer warned me about unhooking ABS on this car - if you do, he said would need to add a bias adjustable master cylinder to tweak the rear brake force manually... you seem to have verified this

what else can we take away from your experiment?

thanks for doing the testing btw!

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bullitt5897

no problem...

Well, my theory is that with running my heavier 20" wheels and stickier tires than Semtex we will find that the icing effect will be magnified. We still have some testing to do with my car once I get it back from GTM. I hope to be back on 19's soon as 20's around Atlanta bend too easily... I believe that will solve some of the issue and save me some costs.

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ChrisSlicks

Some things I can think of that may be happening to you bullitt.

1. Your BBK comes with very grippy track pads. The ABS system doesn't seem to like these kind of pads because they are difficult to modulate, and the cycle time of the controller isn't allowing them to release which causes it to go into an ice mode where it releases the pressure for longer intervals.

2. The ABS system was designed with dynamic brake force distribution. Unlike a traditional brake system which is balanced with a front bias, the dynamic system can send a full 50% of the brake pressure to the rear. It then uses the ABS actuators to modulate the percentage of brake force to the rear depending on the input from the wheel speed sensors. So apparently when the ABS system is disabled it is locking in to a 50/50 split which is going to be pretty useless for manual braking.

3. This one I haven't been able to confirm, but the ABS system may be very sensitive to wheel diameter changes, and is unable to auto-calibrate. The people that are experiencing the biggest problems with the ice-mode effect seem to be running after market wheels and tires. When I asked my dealer mechanic (the GTR master mechanic) if the wheel diameter could be programmed, he said no. Now I'm not sure if that is no, there is no way to do it, or no, he has no clue how to do it.

Has anyone with stock tires experienced ice-mode? Please speak up!

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semtex

That my car is awesome. (j/k)

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bullitt5897

Yes Ben we all know you got a Wed car freak of nature that powns all!!! Lol

in all seriousness. I believe I am running EBC Blue street pads. I will have to ask Mike @ blackline... Other than that I believe the larger wheel diameter and extra weight on each wheel are what's getting me. On certain road surfaces the car is a monster in braking while like our test arena it has an 80ft braking distance... Once again owned by Ben. Dangit ben if you go fi you better go epic big!!! That's one area I won't let you beat me hahahaha!

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Shop Cars: 2013 318whp Nismo VspecII 370z *SOLD*, 2009 1000hp+ 93oct 4.0L TT 370z Fast Intentions STAGE 4 #054

RCZ

Very nice guys, good info. What kind of different surfaces are you talking about Bullitt? Grippier more even roads should minimize this problem.

Chris - I have experienced it on track (smooth, grippy surface) with stock wheels and tires.

This sucks, it's going to take someone getting into a serious accident for anyone to do anything...

ChrisSlicks

What pads were you using at the time it happened?

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bullitt5897

On typical road surfaces that are fairly new and well still grippy the car does well. Places that are recently paved and haven't fully cured or concrete like surfaces that are smoother in nature tend to have a worse effect... I would really like nissan to come out with a patch to make the ABS a little less aggressive.

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Shop Cars: 2013 318whp Nismo VspecII 370z *SOLD*, 2009 1000hp+ 93oct 4.0L TT 370z Fast Intentions STAGE 4 #054

spearfish25

When I first installed the Carbotechs, every brake stop would activate the ice mode. On the track yesterday, more progressive braking didn't get a single icing incident (thank God). However, I was definitely not diving into corners given my apprehension for icing and just rolling right off the track. Every time ABS came on, I started to pucker and thought I was about to get ice'd. It sucks not being able to fully trust your brakes.

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RCZ

Stock everything Chris, except for fluid of course, but that made no difference.

ChrisSlicks

I'm asking because with stock pads it may have been pad fade in that case. The pad fade feels almost identical to the ice mode except that it keeps getting worse as the heat builds.

I've had both so it was all that much harder to figure out what was going on.

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RCZ

maybe uneven fade is causing one wheel to slow down quicker than the rest causing ice mode?

Mike

stock pads and pad fade = total brake loss in about 4 applications.

I've never had the ice mode, even with the brembos. I think though, there is a big difference stopping from speeds in the 100s and even in the 60s with hot R-compounds than in the 40s-60s with street tires.

I'm pretty sure this is only an issue for autocross guys and not track guys.

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cossie1600

Most of the ice mode are with autox guys. I hit it plenty of times during autox, almost never on the track.

bullitt5897

I find the braking styles to be completely different between the two venues. On the track I never lock up the brakes as I am just slowing the car to entry speed where as in an autoX event you practically have to go from 60-0 to make some of those turns... In any case I am going to go back to 19's and see if that solves my issues.

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Shop Cars: 2013 318whp Nismo VspecII 370z *SOLD*, 2009 1000hp+ 93oct 4.0L TT 370z Fast Intentions STAGE 4 #054