997gt3north

Below my post, I have included a bunch of quotes that I found by searching this forum for the words "abs ice mode" - I appear in a few of the treads that show up upon searching.

Final track day of the season - Mosport - ran 5 of 8 possible 25 minute sessions, lots of fun, 2 sessions of the stock OE tires when it was cold and then switched to the R6s - was comfortable doing 1:35-1:36 with the R6s with a passenger in the car (air was cold, grip was fine - it was easy to be fast and leave lots of room for error.

I have always experienced ABS Ice-mode if I over cook it into 5A - easy fix as your speed is slow, release the brakes stab the brakes again - almost always enough time to make turn 5B - if you can't make it - you are going so slow that you just go off and re-enter.

Never in my wildest dreams did I think it could happen in turn #3 (although a poster whose note I include mentioned turn #3 specifically) - coming in at 190kph got to get down to about 100kph - plus 1/2 of the braking is done while turning as the track goes big-time right.

Well, hit the brakes, hard brake pedal (maybe 25% braking) we go straight off and into the tires - body shop says car is very fixable - just body work, etc.

Many would think that I'm crazy for posting this but I think it is paramount to let people know about the seriousness of this issue - it is truly potentially very dangerous and really needs addressed by Bosche / Porsche.

I am not talking about:
- the bumpy brake zone induced ABS float through the brake zone issue
- or the unload the tires (similar to above) (turn 5A Mosport issue)

I'm referring to the instantly hard and firm pedal that only gives you 25% braking force issue - somehow a certain set of circumstances (see notes below) triggers this and the default computer ABS coding puts the brake pressure to 25% or so (I think this is insane) and you can now count me as a victim - I was referred to another individual that is also a victim (it was very expensive for this individual)


So, I am left with a few thoughts / questions

- do we think Porsche / Bosche knows about this issue and is doing nothing? - i.e. is this somehow the best of least preferred outcomes for a street car (i.e. screw the people who might take it to the track we have to protect the street driver first - except for high speed track stuff kills doesn't it?

- the RMS is such an obvious issue and Porsche pretends it is not happening - would they ever admit to this issue?

- does anyone know anyone at Bosche that they can inquire about this?

- does anyone know anyone that damaged a car because of this?

If you would like to email me directly with information on this issue I am contemplating writing an article about it for one of the Porsche Magazines - or would happily ask a regular writer to do so (mail.oneil@gmail.com).


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Below is a compilation of quotes about ABS Ice-Mode I found searching this forum



From Rennlist (997gt3 forum - search ABS Ice mode)

I had this experience as well. (stock PCCB's, Stock tires) It's one of the main reasons I got rid of the car. I'm too chicken to track a car with brakes that don't produce predictable slowing. It only happened to me first session of the day ( but I would defer to mooty's much greater experience with the car on track). Firm pedal (no pulsing ABS feeling, no lockup) but no significant slowing. I've experience the joys of boiled fluid fade, green fade, and pad knockback in other cars. This didn't feel like any of those. I think it may be a problem with the programming on the ABS. It felt like the brakes on my old turbo driving on ice. Hard pedal with no pulsing but no braking action.

I am pretty sure this is a problem with the ABS programing and the brake bias. Under hard braking, it will first go into ABS mode and then beyond that you get a hard pedal and the car will not slow. Fresh pads, old pads, green pads, black pads, old rotors, new rotor, cross drilled, slotted, Castrol srf, you name it, does not make any difference. Like someone mentioned, if you back off and gets back on again, you get your brakes back. It is NOT fade and is NOT fluids boiling because the brakes will be fine at the next corner. That's the way Porsche decided to set up the car. It the track is a little bumpy and you are not perfectly straight when you brake, the tail dances a lot. Some genius at the factory decided to increase the rear bias. Eventually someone will figure out what it is and how to fix it. The Porsche reps I spoke to refused to comment since we are not supposed to take the car to the track. Very annoying. The guys who have GT3s who says they don't have this problem have not braked hard enough. All you have to do to experience this is to go another 20 feet deeper beyond where you normally brake and try it. Promise it will be lots of fun. You basically have to drive around it. The brakes are fine if you just brake at 90%. Since the car does not like trail braking you have no choice but to brake earlier and softer. The upside however is that the car does have much higher mechanical grip so you can actually afford to slow down a bit less and carry a little more entry speed. Still if the factory had done the brakes properly, the car will be even faster in my view. One more thing, for me, it is not long straights, it is usually a downhill bumpy braking zone which triggers this. I never had any problems braking from 165 at the end of the front straights at Pocono. However, Mosport Turn 3 which is at the bottom of the downhill and Watkins Glen at the ankle of the boot which is bumpy as well as downhill is where I get that hard pedal very easily. Turn 1 at the Glen is also downhill but noticeably smoother, I never had the problem. So I don't think it is purely a speed issue. It is when you try to slow in a hurry and the surface is not allowing you maximum grip.

Ice mode is an excellent way to describe this! I think this shall be the official name going forward in my book! Now that you mention it, I had the same twitch at Mosport 8 and I do the same thing, drag the brakes a touch just over the crest, otherwise the tail just goes every which way, although I was probably too worried about the side steps to notice the ice mode. Come to think of it, at Summit Point, the left hander before the carousel is also a hard braking down hill and depending on which side of the track you enter, you can get that ice mode too. I agree with you. It has to be a combination of the rear bias and ABS fighting you when you go over its limit. I think they received so much complaints about the 996 GT3 not having enough rear bias (most guys I know run pagid blacks in the rear and yellows in the front to add more rear bite) that they over compensated for the 997s. If any body know someone at Motorsport, would be great if you can solicit some input on how to fix this.

A couple of weeks ago a took my RS to Sebring for the first time. Going into T9 in dry conditions I had a very similar experience to what Mitch236 reported regarding his steel brakes. namely, when coming hard on the brakes there was less than full retardation rate and theABS was pulsing. I ended up missing the apex by 20 feet or so. Pedal was firm. Did anybody else had this happen with PCCB yet? When I was applying the initial braking more softly, braking was very good. This happened a few times.

Since practically all the brake system hard components are different between steel and PCCB, I think that the problem is rather in theABS controll software. My theory is that since the brake rotors are huge and cooling is improved over earlier cars, when the brakes are hit hard when not fully to temprature, the initial braking is not quite even left and right. The ABS mistakes this for a lockup condition, and therefore regulates pressure i.e. does not allow full braking force. If this is the case the solution may be in a software upgrade from Porsche, but they need to admit there's a problem first...

I'm not the type that enjoys contradicting someone over issues that could be just about anything everyone has stated in this thread but…I've had exactly what you described happen to me several times with my 3.6 GS race car and it wasn’t driver error. It is definitely an intermittent problem. I can't speak intelligently about your PCCB ABSsystem but I will tell you that most if not all professionally campaigned "street type" 997's are running "BMW" (I believe it’s a Bosch system made for BMW) ABS systems. Meaning other than a factory 997 cup car (which by the way doesn't have ABS) as in a Koni challenge GS class race cars. Ask any competent race team campaigning a 997 GS car and they will tell you there is definitely an "issue" with the OEM 997 ABS system in a racing application. The "BMW" ABS modification is approximately ten thousand dollars; they wouldn’t do it if they didn’t need to. So what now since you're not going to rip the ABS out of your brand new RS? Well again I'm not up on PCCB's but I can tell you what I found that the system "didn't like" in a steel application. I found that the more aggressive the brake pad "bite" the more occurrences I had…even after following the manufacturers exact bedding procedures. So for me it was more frequent brake pad changes but less occurrences of the rock solid pedal with no reduction in speed. The other thing I do now is a slight "tap" (as if to wake up the system) then a normal hard brake application. It seems to me like the system doesn't like a hard initial pedal application with OMG grip at the rotor
This "tap" technique was taught to me by a top Rolex driver during a coaching session; he starting doing it after experiencing the same problem and crashing out of a race. I wouldn’t call it a brake check as much as I might call it a test tap…more of a wakeup call to the ABS system…but nothing will slow you down more than going off or hitting something. I found prior to doing it I never really knew if the brakes would "be there" which was a real confidence detractor. The next time you are watching a Koni challenge race and they go to the in car of a 997 try to note the foot work…
his issue is not PCCB / Steel related. It's ABS logic that's at fault. I got around it yesterday by not jumping on the brakes; rather, applying them in a progressive manner. You can't always do that - whic is why I still think Porsche needs to come up with a software fix.

Oldguy, I'm NOT an expert but if you are asking my opinion, I say look at what the pros do. The pro teams are ABSOLUTELY replacing the ABS system on the 997 Koni challenge cars. Additionally, I know several people who have had this problem on the 3.8 S car with steel and PCCB's. Take a look a Synergy Racing's brake package for their 997 race car featured in every Pano or Excellence magazine. I think the stock OEM ABS system "dislikes" aggressive bite racing pads in conjunction with a race car driver application of the pedal in 997's all together. Quirks are only an issue when they are unpredictable, I played with different pads and rotors to try and find a happy place… how many times have you had a long pedal on the track? you deal with it right.…I could absolutely make it happen with Hawk HT10's and several other pads that are excellent on a 996 under hard braking. Additionally, I did not have any of this on my 996 GT3 cup car. Like most people on this forum, I have a new 997 GT3 that I will be using as a track car so I'm hoping for the best possible outcome however until I see the exact same setup on my car being used in a pro racing application I will always remember going off T1 at VIR at a ridiculous rate of speed and use the "test tap".

I am glad to hear someone else is having the same issue with the brakes on the RS as I do. At my first event at Pocono with the RS, I had stock pads and fluids. By the second run of the day, the pedal already felt mushy and I had the same ABS kicking in issue and the car wouldn't stop. Almost like the car was fighting me. With the mushy pedal, at least I felt I was able to stomp on it to make it stop. It was difficult to modulate, nothing like my old 993 which had a much more linear feel. I had to brake early and soft. I was not a happy camper because everything else about the car was fantasic. At the second event, I changed to srf fluids and p50 pads from Motorsport. The mushy pedal issue went away as expected but the ABS issue became much much worse. If you have done Mosport, at the end of the back straight is a fast sweeper. It is a bit bumpy and you sort of have to set the car up with a bit of trail braking to get into the turn. First time I tried it I nearly went off the track backwards. Not only did ABD kicked in, the tail wanted to come out. So it was off brake, counter steer back on brake and counter steer the other way just to keep the car on the track. I was told the bias of the brake is much more to the rear on the 997 GT3 and GT3 RS but whatever electronics they put on that thing, it is doing something very strange with the brakes. I was never able to press the brake pedal beyond half way point (or where it is level with the gas pedal) without triggering some untidy reaction from the car

I've got a disconcerting braking problem at the track that I'd really like to get cleared up. The issue comes up at the end of longer straights when I get into the brakes aggressively. As I get on the pedal, it feels like a rock and I get substantially less braking than I normally do at the exact time that I need it most. The rest of the time, the braking setup is superb, but this is a big issue that has scared the heck out of me several times now. Pressing the pedal harder doesn't help. Sometimes, backing off and getting back on does help. I can prevent it by getting on the brakes earlier and softer, but sometimes that defeats the purpose of trying to get around the track as quickly as possible.

i get that periodically and always at end of long straights, go figure. if i decide to brake late and really jam on the brakes, 5% of the time this will happen. hard pedal, no stopping power. it's not ABS prob, i have experienced those before, totally different. but if you let of pedal and quickly reapply pressure, it's back to normal. it happens with new/old pad and/or new old rotors and any combination there of.

since this has also happened to me in both the gt3 (irons) and the RS (pccb), I can relate to your squeamish feeling of hopelessness- what I will say is that it felt to me like the brakes simply overcame the tire's grip...but like mooty says, if you can catch it quickly then reapply you're fine.

not my case. sometimes i drove all day no problem, by session 4, say lap 5, one hard pedal, then never happen again.. 4 months later, new pad, or old pads, end of end or first session of day.. happens again. there's no consistency on when it happens, EXCEPT always at end of long straights.

In regards to the ABS problem, I had it with the RS at every track I went, I don't recall to have experienced the same issues with my 996 GT3. It's noticeable on bumpy braking areas coming from very high speeds (120+ mph).

I had two rounds of "ice mode" braking there before backing off and braking a little earlier. Was doing over 125 before hitting the braking zone and trying to dump a lot of speed in a short distance

grussell

Sorry to hear that. I too had the same problem on my GT3. I was never able to fix it but fortunately I never had an incident other than going off.

amg6975

First post here, hey everyone... Same thing happens in the Lotus crowd, they solved it by adding a bigger vacuum canister, better check valve and triple checking all connections. It was happening due to vacuum pressure in the stock canister dissipating over long straights under WOT then trying to jump on the brakes with no juice in the brake booster.

WHB Porsche

Is there a motorsports ABS unit that can be used? Not that this is excusable, but it would be good to know that other GT3 users have options.

997gt3north

i believe this theory was postulated by a gt3 / lotus owner and later proved incorrect - could be wrong

i have tracked with him and he stated such in a rennlist post if i'm correct

PointBy

This also has happens in my Audi A4 that I tracked. Specifically, Cal Speedway going into the left hander after the long straight. No vacuum boost leaves a hard pedal and no power brakes. With only mechanical brake torque it's impossible to stop in time. Luckily there, its possible to go through the barriers and not make contact.

Terry L

Paul is correct. The vacuum dissipation was my theory but turned out to be incorrect. I believe that the Lotus factory eventually conceded that the problem was real and came up with the correct explanation - I just don't remember what it was! If I can find it on the Lotus board I'll let you know.

Terry L

Here is what was posted on the Lotus board: 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.

Md11skipper

Turn off the engine while the car sits on a slope after the engine stopped let the car roll down hill, if you have servo support (vacuum) then the check valve which is supposed to keep the vacuum, functions. If you step on the brakes the first time and it feels like there is no vacuum support, then the check valve is leaking. This could be one reason why you did not have brakes available after a long straight because the check valve did not keep the vacuum while you had the throttle open, hope that makes sense.

MarekN

Very interesting and informative. In regards to Bosch/Porsche, we all know that with any specific subject of this type and in such detail, there will be no official communication with us. Maybe some of the guys who get to meet Preuninger and other engineers at the RS previews which are now lined up in Europe may have a chance to bring this up.

I sometimes get this effect also at the end of long straights after full throttle. I have PCCB. I found by trial and error that I have to release the pressure and then re-apply it again and it works just like described above. I partially blamed cold brakes when that happens, but when I tried to heat them up before this one spot where it happens (braking from 180 km to 80 km), it happened anyway. It´s true that at this place I am braking and slightly turning the wheel, which may have the issue with EBD. On the other hand, the road there is glass smooth...

What about turning off the fuses?

YearOne

Given that the GT3 is a track biased car I think they should come with switchable ABS like the F355s did.

grussell

I had this problem with my 2007 GT3 with steel brakes and I have this problem with my 2007 GT3RS with PCCB. It happens during long threshold braking and is unsafe on the track unless you brake early.

I was unable to resolve the issue even after changing to Brembo GTR's. What finally solved the problem was replacing the ABS unit with the 996 Cup Bosch unit.

What I would really like to know is if this issue is fixed in the 997.2 GT3 and GT3RS. If it is not, I will not buy one.

997gt3north

Since the 997.2gt3 has SC in addition to TC (yes both defeatable with push of button) the ABS modules are likely not the same - it may however be very similar to the 997gt2 module / logic as the GT2 comes with both SC + TC (the SC being the rear brake pad killer that we have all heard stories about with abrupt throttle application) - and if you search "ice mode gt2" the same issue comes up so i'm guessing the new car suffers from it as well.

And, the day i went off, there was a 2010gt3 with pccbs - and he said he was having the issue in turn #3 (where it happened to me) so i'm guess that nothing has changed

Paul

NJ-GT

ice mode happens to the Lotus Elise/Exige, the Corvette Z06, the Boxster/Cayman.

Replacing the ABS module with a Motorsports unit is a well known fix by race shops for street cars, not cheap though, I think it is something like $10k.

machina

Could the ABS problem be related to the tire/wheel slip problem so many of us are having?

I have still not found a way to keep my R6's from rotating on my CCW wheels. Hoosier told me to try myers tire paste but it made no difference.

Thinking that if the wheel is rotating in the tire under braking it could be throwing off the ABS control and diminishing braking.

As of my last event I was still turning all 4 wheels in the tires under braking.