Braking problem - malfunctioning ABS

travisjb

That sounds good.

The expensive fluid won't lower temps as you know, but will have a higher b.p. So, you still may have an ABS sensor that gets excessively hot, and as you say, you will only be able to rule out fluid boiling as an individual cause.

Where are you pointing the air if not at the inside of the rotors? How far away is the outlet? Perhaps if you can point them towards the ABS sensor we can test the theory of sensor overheating as a cause.

The other one we need to test is differential wheel spin...

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2009 370Z #104
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ResIpsa

The ducts are pointing (as best I could) to directly under the brake caliper. I connected the end of the tubing to the lower part of the shock absorber. I would guess about 4 to 6 inches from the rotor. The main problem is the shape of our front spindle. It really blocks access to the inside of the rotor. In hindsight, I should have cut off the entire dust shield but I don't have a proper sheet metal shear (and I was getting tired).

I should have taken some pictures but I was not all that anxious to display my ghetto-cooling ducts. And it did take some cutting of the inside fender cover...


Keep in mind that I was retrofitting my fang ram air setup and this limited the length of my brake tubing.

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cossie1600

Yes I understand the difference between the ice mode and brake fade. At autox, there is no way you can generate enough heat or speed to fade the brakes. What I felt was clearly ice mode where the brakes would just pulsate and not stop. The C6 was notorious for thatThe RX-8 rarely got into ice mode compare to the Z and other cars.

Ice mode is normal as to prevent brakes from constantly locking in the snow

travisjb

chris, we need to construct tests for these theories... to rule out (or in) the heat theory, we need to measure temperature on the calipers and rotors and conduct trials... not sure how to test temp of the fluid though

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2009 370Z #104
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ChrisSlicks

I could measure the temperature of the hard brake line at certain points. In theory after a 10 minute sit the line that wraps the fluid should be close in temperature due to conductive heat transfer.

Okay for caliper temps I can use the temperature stickers and probably a portable laser thermometer (should read high enough). I will get some paint for the rotors and will see if 1400F is enough for the pyrometer, the 1800F unit is more expensive.

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ChrisSlicks

Ok picked up an Infrared thermometer from Grainger, it's good up to 1832F. If anything on my car gets that hot I expect spontaneous combustion!

Extech 42512: Dual Laser InfraRed Thermometer

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the_student

Suscribed

AutoX Z

So I finally experienced this at the last event. Last run on the day with a very hot and tired car. Noticed the ABS engage wayyy too early on the second to last corner then coming through the finish had almost no brakes, very strange feeling.

Car has all stock brake components with Hoosier A6's.

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RCZ

^ Sounds like fade? Maybe you glazed the pad?

Sorry to go offtopic folks, but I want to get in on the fun too. Where are you all buying your Carbotech pads at?

sig11

Forged gave me a pretty reasonable price.

ChrisSlicks

Same thing happens to me. I thought it was fade at first, but the ABS ends up pulsing the front brakes, not the rear. If the fronts were overheated you would expect the rear brakes to be doing all the work and locking up as a result.

Something is f-d up in the ABS program (of which heat is an apparent factor). I'll know more this weekend after taking some measurements.

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AutoX Z

No it wasn't brake fade. The brakes were fine all day and the amount of pedal travel/effort required to stop the car never changed the ABS just started engaging well before it should have. What doesn't make sense to me is if it was a straight programing problem the ABS would go into ice-mode from the first stop. The fact that it also seems to be temperature related is very puzzling

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gpa7pk

Go directly to Carbotech - Carbo Tech, Inc.* - they have our pads in stock, can offer a pad bedding service so that you just install their pads and go (I haven't installed mine yet). They are very responsive with fast and reasonable shipping.

sig11

I think you mean Carbotech Performance Brakes

RCZ

ABS systems are supposed to activate when the speed sensor at each corner notices the tire slowing down faster than it is physically possible for the entire car to slow down. When it reaches a threshold, it releases brake pressure to that corner until it senses some acceleration back from that tire, immediately after it lets it decel again until it reaches the threshold and the process starts all over.
I don't think our system is malfunctioning, in fact I think its working too well. It just thinks its going to loose traction immediately after it reapplies pressure. I think the parameters of the ABS system are simply too conservative to be taken on the track, problem is that if they were what we wanted, then we would have inexperienced drivers (read: the same idiots who crash when they turn vdc off) crashing in the rain all the time.

So put yourself in the shoes of the mfg, they would obviously rather a bunch of us enthusiasts bitch that we can't use our cars on the track that well, than people crashing and dying.
It happens to GT3's and Exiges all the same. The only thing we all really have in common is that the ABS system needs to be there to keep people in one piece and needs to undergo rigorous testing to meet standards.

At the same time, I realize that if the system were working properly, it should detect a point in which the tire deceleration can in fact keep up with the car's overall deceleration and stop the ABS system. If the ABS were programmed for big sticky tires such as the ones we have stock, that should minimize the intrusion of the system. It would allow for a more aggressive discrepancy between car decel and tire decel. I think thats too expensive though, to develop a customized ABS system specifically for this car and specifically for us track goers. They would rather probably use the same system as they do in the sentra, maxima and cube. Not to mention the problem again becomes; what happens when that same car is in the hands of soccermom late for practice in the rain?

The only way I can see us getting around this problem is turning abs off or having a system that is designed to allow more aggressive tire compounds. As someone already pointed out, that option is the BMW system that is $15,000.

I wish we had some sort of "Track" button that would switch us to a more aggressive ABS tune. I'm pretty sure Ferrari has such a system implemented within their manetino steering wheel system, but that's why they are $250k.

Anyone ever heard of a way to reprogram your ABS parameters?

In other words, I hope we find something punctual that is specifically causing the ABS to go and remain in icemode, but I have a feeling its just the system doing its job in what it is programed to think is a "complete panic stop". I can guarantee you all that the guys with GT3's out there, who have a little bit more resources than most of us do, (I said most, congrats if that doesn't include you) would have found a fix for this already if it were a hardware malfunction.

Just my .02 and on that note I will also add that I'll be looking for a punctual issue just like you guys. I'm just a little skeptical considering the facts.

EDIT: by this logic...folks with BBK's and stickier tires might be more prone to going into icemode. Maybe we need pads with less initial bite or less brake pressure. I'm just throwing ideas out there that might make someone put two and two together and say "Aha!". Not to mention it should happen less and less and not more and more as our crappy stock pads get hot and begin to fade, but that doesn't seem to be the case either.

Does anyone know what the BMW system replaces? Do they mention any components that hold up better to heat??