Braking problem - malfunctioning ABS

RCZ · 03-15-2010, 01:44 PM

Well this one has me really bummed. I thought we had solved this problem with brake upgrades. So its an ABS problem after all..

It hasn't happened to me in a while, but quick comment: I remember the first time it happened, it happened fairly quickly. Seemed like there was no warning, however the second time it happened, I felt the brakes gradually get worst and worst and then decided to really get on them when I thought they were about to fail and they did.

What I'm trying to get at is that it gradually built up to the point of failure, rather than being an on/off issue.

Considering that Travis switched his Calipers, rotors, pads, lines and fluid and its still happening AND in my experience it was a gradual failure (please others chime in, gradual or not?).... my first guess would be that it has something to do with heat buildup affecting a sensor in the ABS system.

Thoughts on that theory?

travisjb · 03-15-2010, 01:50 PM

I don't think it is a heat issue, but will know more after this coming weekend when I test with temp paint / strips... when it happened this last weekend, i was 2 laps in... i have a trusted source as well that confirmed it is a variable wheel spin instigated problem - will PM you on this

RCZ · 03-15-2010, 01:53 PM

Sure, if that's the case then we need to figure out how to fix the issue. Problem is that its very difficult to get anything done by Nissan. I mean...over a year in and we still don't have a real fix for the overheating....they aren't going to do anything for us here. I think aftermarket is going to have to take care of this one...hopefully Stillen can figure something out. I hope it is a simple issue rather than a combination of issues which will make it much harder to pinpoint the problem.

Josh@STILLEN · 03-15-2010, 02:25 PM

travis, do you have anyone with access to a Consult that could see if there's any codes in the ABS system?

spearfish25 · 03-15-2010, 02:49 PM

Can anyone confirm that immediately releasing and then reapplying the brakes resolves the issue? I think this was briefly suggested a few pages back. Could be a life saver if it's true and the knowledge disseminated.

travisjb · 03-15-2010, 03:04 PM

Quote:

Originally Posted by spearfish25

Can anyone confirm that immediately releasing and then reapplying the brakes resolves the issue? I think this was briefly suggested a few pages back. Could be a life saver if it's true and the knowledge disseminated.

I believe I tried pumping but may not have fully lifted my foot off the pedal... so can't confirm 100%... we need to try and 'create' the condition in a parking lot so we can isolate the circumstances more precisely

travisjb · 03-15-2010, 03:04 PM

Quote:

Originally Posted by Josh@STILLEN

travis, do you have anyone with access to a Consult that could see if there's any codes in the ABS system?

As it turns out, I have my car at a local nissan dealer today for an unrelated BCM/ECM issue, and I may be able to get them to do this

RCZ · 03-15-2010, 03:31 PM

Don't know if this will help. It appears that Porsche/Lotus also have this problem.

well, ABS Ice Mode finally got me... - Rennlist Discussion Forums

EDIT: Add Corvettes, Camaros, Mazda, Audi....

RCZ · 03-15-2010, 03:32 PM

Quote:

Originally Posted by spearfish25

Can anyone confirm that immediately releasing and then reapplying the brakes resolves the issue? I think this was briefly suggested a few pages back. Could be a life saver if it's true and the knowledge disseminated.

I pumped immediately since I'm used to it from karts, but it didnt change anything.

EDIT: More info

Quote:

"The symptoms being described are a result of the Electronic Brake Distribution (EBD) system operating. This system is also referred to as Dynamic Rear Proportioning (DRP) and is, as the name implies an electronic system which, through the ABS control valve block restricts the line pressure to the rear brakes automatically to a pre-programmed algorithm. You can consider it as an electronically controlled proportioning valve which measures parameters like the rate of deceleration and rate of pedal application and uses this data to anticipate a rear wheel lock-up and then reduces the braking effort at the rear wheels as necessary. If the ABS system is left to do this, it can only react to a wheel as it starts to lock and therefore the car can already start to spin before the ABS can start to work. In extreme circumstances, if the driver brakes very suddenly the EBD system can lock off the pressure to the rear wheels completely; what pressure was at the rear brakes as the EBD system engaged remains there and the rear brakes are still working as a result, but further increases in pedal effort will not increase the braking at the rear of the car because the pressure to the rear brakes cannot increase. When this happens the brake pedal goes hard, as it is now pushing against the front callipers and a closed valve only, instead of against the front and rear callipers. The rear callipers are single piston and therefore quite flexible, so they are a major factor in making the brake pedal feel 'soft'. When the valve closes, the brake pedal pressure no longer flexes the rear callipers, hence the increase in pedal hardness. The front brakes are still working just as well as before the valve closed and will give more braking if the pedal effort is increased, while with the rear brakes working as hard as they can the braking is NOT affected. The problem is the driver feels like braking is reduced (even though it is not) because of the change in pedal feel. If the driver continues to push hard on the pedal, the car will continue to slow as fast as it possibly can in the circumstances. If he increases the pedal effort the front braking effort will increase and the rear effort will remain where it was. If he was to back off the pedal for a fraction of a second, the valve will reopen and the rear brakes will operate as normal again, with the pedal feel going back to normal.

In the case of releasing and re-engaging the pedal the car should not be able to slow any faster than it was with the system engaged unless either 1: the driver triggered the system in the first place by stamping on the pedal too fast or 2: the system triggered because a rear wheel was unloaded when the brakes were applied and would have locked up but is now fully loaded once again and able to sustain a greater braking torque. If the rate of deceleration does improve when the pedal is reapplied then it is telling the driver that he is over braking either in terms of the ultimate ability of the brakes (cause 1 above) or the track condition (cause 2 above) and needs to adjust his driving style to suit. If the system were not fitted or disabled and he continued to drive that way he would be in danger of spinning when applying the brakes.

The suggestion that the system is running out of vacuum is just plain wrong. The system carries an internal reservoir of vacuum sufficient for three full brake applications. As with every servo system ever fitted to a car there is a one way valve which prevents the vacuum being lost when the car is on boost. The only way this reserve can be depleted is if the driver is maintaining boost while applying full brakes, i.e.: left foot braking very badly. In this instance I would argue that depleting the vacuum is probably a good thing as it should provide him with a warning that he is doing something awful to the car and it may reduce the speed of impact when he finally hits something as the brakes fade to nothing!! In normal use the throttle is closed when the brakes are applied, there is therefore no boost and the vacuum is automatically replenished as it is used.

travisjb · 03-15-2010, 03:54 PM

Raul, brilliant! I was just about to cross-post the exact same quote... #8 on the other board... the only problem with the theory is I remember pushing pretty hard on the pedal and not getting more braking response... I'm not certain this is spot on but... Stillen, this is prob the first thing you guys should look in to

RCZ · 03-15-2010, 04:07 PM

Quote:

Originally Posted by travisjb

Raul, brilliant! I was just about to cross-post the exact same quote... #8 on the other board... the only problem with the theory is I remember pushing pretty hard on the pedal and not getting more braking response... I'm not certain this is spot on but... Stillen, this is prob the first thing you guys should look in to

Yup, I saw this posted on several sites...mainly because its the only explanation they have found coming from a credible source.... Lotus to be specific. I saw the explanation of the problem, but nowhere did I find a fix.

Best solution I've seen so far is disconnecting the abs sensor and threshold brake....not a bad suggestion on a dry circuit. Not for newbies.

didymus · 03-15-2010, 04:27 PM

Could this be related to what is discussed in this thread? ie: ABLS?

http://www.the370z.com/nissan-370z-g...etely-off.html

travisjb · 03-15-2010, 06:37 PM

no, different issue

AP - Chris_B · 03-15-2010, 06:50 PM

Quote:

Originally Posted by travisjb

Stillen, this is prob the first thing you guys should look in to

I have seen ABS "ice mode" on the Elise/Exige, working with quite a few drivers who did not like it one bit! Lotus eventually offered the "fix" in a Motorsports ABS module upgrade (something like $10k, IIRC). I don't know if the module is available for the street cars or just the Cup track (not road-legal) cars.

In the short term, it is best to get to the track and practice initiating the braking event. The key is to not stomp on the brake pedal. It can be firmly applied, but the ABS module looks at how fast the system pressure rises. If it senses a huge spike, the algorithms determine that you must be in big trouble and are about to have "a moment". The brake gods then take over and you are pretty much a passenger until you let off the brakes and try again. Of course, now you are in full panic and hit the pedal even harder, spawning another ice mode experience!

The best (at least the most colorful!) description I ever heard from a pro driver about proper braking technique came from Roberto Moreno when he was in the Swift chassis at Long Beach years ago. We were working on aero mods that would lessen the forward center of pressure shift under braking. On the road courses, the suspension would need to be run higher and softer for the bumps, so the car wanted to dive under braking and lift the rear. This lift "unsealed" the underwing tunnels, losing rear downforce. Working day and night in the wind tunnel to come up with solutions, we ended up with a car that had a big advantage going into the heavy braking zones. Roberto was so excited when getting out of the car after the first practice, proudly stating that no one could outbrake him. When I asked him how the car was reacting, he said it was "Perfect, like I am making love to the brake pedal." Uh, use your own judgment when interpreting that last statement.

For the long term, it would be best to continue to go to Nissan with the issue in hopes they offer a way to change it if enough people complain. There is nothing Stillen can do to modify the ABS that doesn't require more lawyers than currently out of work (sorry, under-employed) in southern California. One bad incident on the street in cold weather with a modified module and we'd all be looking for jobs!

Aftermarket brake companies should carry a serious product liability insurance policy (your does, right?), but modifying ABS modules would be a great way to get dropped quicker than the next guy to marry Pamela Anderson.

Chris

P.S. Roberto passed a lot of cars on that race day -- until one Mr. Tracy thought better of giving him enough room to get by. Two cars cannot occupy the same space at the same time!

RCZ · 03-15-2010, 07:02 PM

^ Nor can a car and a wall and thats our big issue right now... luckily my local track has nice braking zone run-off's so the worst I have to worry about is getting dirty or clag on my tires.

Thanks for the input Chris, very helpful! So long story short we are SOL until Nissan decides to (yeah right) help us out with a less safe ABS system.

03-15-2010, 01:50 PM	#47 (permalink)
travisjb A True Z Fanatic Join Date: Jan 2009 Location: GSO Posts: 2,803 Drives: VIR Rep Power: 188	I don't think it is a heat issue, but will know more after this coming weekend when I test with temp paint / strips... when it happened this last weekend, i was 2 laps in... i have a trusted source as well that confirmed it is a variable wheel spin instigated problem - will PM you on this __________________ 2009 370Z #104 For Sale

03-15-2010, 02:49 PM	#50 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1856	Can anyone confirm that immediately releasing and then reapplying the brakes resolves the issue? I think this was briefly suggested a few pages back. Could be a life saver if it's true and the knowledge disseminated. __________________ 2013 Cadillac V-Wagon, RIP Z

03-15-2010, 03:31 PM	#53 (permalink)
RCZ A True Z Fanatic Join Date: Nov 2008 Location: Miami Posts: 6,403 Drives: '09 370Z Rep Power: 1118	Don't know if this will help. It appears that Porsche/Lotus also have this problem. well, ABS Ice Mode finally got me... - Rennlist Discussion Forums EDIT: Add Corvettes, Camaros, Mazda, Audi.... Last edited by RCZ; 03-15-2010 at 03:33 PM.

03-15-2010, 03:54 PM	#55 (permalink)
travisjb A True Z Fanatic Join Date: Jan 2009 Location: GSO Posts: 2,803 Drives: VIR Rep Power: 188	Raul, brilliant! I was just about to cross-post the exact same quote... #8 on the other board... the only problem with the theory is I remember pushing pretty hard on the pedal and not getting more braking response... I'm not certain this is spot on but... Stillen, this is prob the first thing you guys should look in to __________________ 2009 370Z #104 For Sale

03-15-2010, 06:37 PM	#58 (permalink)
travisjb A True Z Fanatic Join Date: Jan 2009 Location: GSO Posts: 2,803 Drives: VIR Rep Power: 188	no, different issue __________________ 2009 370Z #104 For Sale

03-15-2010, 01:44 PM	#46 (permalink)
RCZ A True Z Fanatic Join Date: Nov 2008 Location: Miami Posts: 6,403 Drives: '09 370Z Rep Power: 1118	Well this one has me really bummed. I thought we had solved this problem with brake upgrades. So its an ABS problem after all.. It hasn't happened to me in a while, but quick comment: I remember the first time it happened, it happened fairly quickly. Seemed like there was no warning, however the second time it happened, I felt the brakes gradually get worst and worst and then decided to really get on them when I thought they were about to fail and they did. What I'm trying to get at is that it gradually built up to the point of failure, rather than being an on/off issue. Considering that Travis switched his Calipers, rotors, pads, lines and fluid and its still happening AND in my experience it was a gradual failure (please others chime in, gradual or not?).... my first guess would be that it has something to do with heat buildup affecting a sensor in the ABS system. Thoughts on that theory?

03-15-2010, 01:53 PM	#48 (permalink)
RCZ A True Z Fanatic Join Date: Nov 2008 Location: Miami Posts: 6,403 Drives: '09 370Z Rep Power: 1118	Sure, if that's the case then we need to figure out how to fix the issue. Problem is that its very difficult to get anything done by Nissan. I mean...over a year in and we still don't have a real fix for the overheating....they aren't going to do anything for us here. I think aftermarket is going to have to take care of this one...hopefully Stillen can figure something out. I hope it is a simple issue rather than a combination of issues which will make it much harder to pinpoint the problem.

03-15-2010, 02:25 PM	#49 (permalink)
Josh@STILLEN The370Z.com Sponsor Join Date: Dec 2008 Location: Costa Mesa, CA Posts: 1,197 Drives: 2004 G35 Coupe 6MT Rep Power: 533	travis, do you have anyone with access to a Consult that could see if there's any codes in the ABS system?

03-15-2010, 04:27 PM	#57 (permalink)
didymus Track Member Join Date: Jun 2009 Location: Providence / Boston Posts: 564 Drives: 280 / 370Z Rep Power: 305	Could this be related to what is discussed in this thread? ie: ABLS? http://www.the370z.com/nissan-370z-g...etely-off.html

03-15-2010, 07:02 PM	#60 (permalink)
RCZ A True Z Fanatic Join Date: Nov 2008 Location: Miami Posts: 6,403 Drives: '09 370Z Rep Power: 1118	^ Nor can a car and a wall and thats our big issue right now... luckily my local track has nice braking zone run-off's so the worst I have to worry about is getting dirty or clag on my tires. Thanks for the input Chris, very helpful! So long story short we are SOL until Nissan decides to (yeah right) help us out with a less safe ABS system.

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