Nordschleife

Noah
The only clue is that this was done AFTER everything else was switched off, so no driver aids atall

R+C

IMGT3

The programing algorithms found in the 996 & 997 GT3 are different. ABS Ice Mode, as has been discussed in this thread is (I believe) closely related to the oe equipment spec (specifically tires) that are factored into these multiple scenarios that these algorithms emulate on the 997 street car. Cup, RS and RSR have different variables factored in, such as the use of slicks being common place. Why not on the 996GT3? Can't say, but our drivers 6GT3 rotates between Sport Cups, Michelin Slicks and Hoosiers without experiencing this problem. We have others!

Chuck

Nordschleife

Chuck

The standard Cup car does not have ABS (so easy to change tyres, its all down to driver talent), the R does have a race ABS system and is targeted at non-professional drivers in GT3 class races. The RSR also does not have ABS.

Some race series do allow entrants to retrofit ABS on their GT3 race cars. The Bosch ABS M4 kit can be set up with multiple programs. This link points to the ABS M4 kit manual

http://www.bosch-motorsport.com/cont..._Manual_en.pdf

Required reading for anybody interested in brake issues.

I do not know about the US Cup series, but most (all?) other cup series for current model cup cars do not have ABS.

The MS ABS allows entrants to turn off any or all of ABS, EBD and TC.

R+C

turbo911cm

So the moral of the story, if you have a GT3 and plan on modifying the suspension, tires, wheels, etc. you should also plan on spending more money on an ABS M4 kit as well (plus programming of the kit). If you don't you run the risk of ice mode.

Man if I was a 7GT3 owner I would be pissed!!!!

Those 993's and 996's are looking better and better for track duty.

Terry L

I was shocked to be told recently that 997 Cups don't even have power assisted braking! All that brake force comes from the driver's right leg. Is this correct?

IMGT3

Off course your right! I can only attribute that mistake to staying up too late! Thank you also for the link! Looking forward to hearing your additional comments. Chuck

mooty

yes, feels like brick

Carrera GT

Ha! This is something I've been arguing in favor of since the 964! There's still no better way to get the pedal feel (and unassisted steering feel) that is otherwise dulled or even deleted by "power" systems. The hydraulic amplification of the manual braking system is ample to generate 1000+ brake horsepower; how much more is needed?!

jyoteen

I've been reading this thread with utmost interest. Just very recently, I experienced this ABS ice mode on a sweeper.

Conditions: Dry, night, mostly smooth pavement, Road was a left hand sweeper, on slight camber, headed downhill.

I take this sweeper at least twice a day, and i'm very familiar with the speed and always leave something on the table. I hit the brakes (trail braking) and suddenly, for the first time, the pedal firmed up to the point where I was definitely not decelerating.

I let off the pedal slightly and applied pressure again, trying desparately to slow down, which I did enough to continue on, but the re-application of the pedal freaked the abs/PSM/etc out a bit to much.

We came to almost a stop and then the dash lit up like a christmas tree. I've had this before in another instance, but never bothered to remember the exact circumstances.

I believe it's the wheel speed/ABS sensor. Now, I'm not sure whether it's the sensor ring or the actual ABS unit or another black box in the car. I've had this happen in my S4 too on the track and I chalked it up to freaking the ABS/EBD out and going beyond a certain parameter (yaw/steering angle/braking combination)

Anyhow, I'd add my two cents. BTW, I got home, turned off the car and turned it off and the car didn't seem to think anything else was wrong. The fault hasn't returned, but i'm sure I can try for another round if I want to be brave.

I happened to grab my phone

http://www.youtube.com/watch?v=ki2vo...layer_embedded

Carrera GT

Interesting. I've had instances (in a 2010 car, but not in the 2007) where, after a "mishap" the dash would report variously "SC failure" or "ABS failure" and I've not found an explanation other than once the car has gone through "implausible" events (extreme contradictions between sensors such as wheel rotation and accelerometers) the system decides to throw its electronic hands in the air and quit.

I've not had the ice pedal in street driving. I think the next time I'm at Laguna, I'll be running video and data acquisition, perhaps including a video camera on the pedals, and spend a few sessions trying to repeatedly invoke ice mode as many times as possible to try to make it reveal its root cause. I'm all for going to non ABS and non power-assisted brakes!

FFaust

jyoteen, had you had a chance to get the OBDC read? Wonder if any faults would have been recorded...

911SLOW

Great idea! It's one of the few things "never been caught on tape before". : )

Terry L

I believe the mechanical advantage is around 5-1 from the pure hydraulics. How would you calculate brake force needed from the driver's leg to generate this bhp?

jyoteen

No, not yet. I go into my shop next week and will get a readout for sure. The CEL, ABS and the PSM lights all went on at the same time (and went off after a car restart) so I'm hoping something got recorded.

I'm definitely having the ABS wheel sensors looked at. They're original.

I'll report back. Odd, indeed.

Carrera GT

It's a matter of the work the pads and rotors can produce at say 60 or 100 mph, not the ratio of pedal force to caliper piston clamping force. I'm sure there's some brake design sites or "how it works" pages at some of the vendors like stoptech to explain swept area, heat production, leverage, as well as clamping force, friction coefficients, etc. Perhaps the pad makers like Pagid would have formulas (formulae?) for each of their compounds operating against a given rotor composition or alloy.

Whatever the engineering, while we think of "powerful" engines in the 500hp range and capable of sending the car to 100 mph in three seconds or whatever, the brakes are twice as powerful (or more) and can bring the car back to a halt in a matter of 80 feet (or 120 in the case of a BMW.)

I'm usually trying to threshold brake at the limits of the tires' adhesion and do this with my big toe. I am curious to see what happens if the booster is removed from the channels of communication and I might have to use all my toes to modulate the pedal. Or maybe I'll crash.