BGTV8

In August 2003, Stewart McColl died sa a consequence of an accident in the braking area into turn 4 at Philip Island whilst competing in the Australian Production Touring Car championship in a Volkswagen Golf (I think an R32 from memory, but I may be mistaken).

The coronial enquiry concluded (based on datalogging presented to the court by "specialist engineers" whose attribution does not appear in the court records) that the root cause of the incident leading to the driver death was small bumps in the circuit on drivers left (T4 is an 80kph right hand hairpin) approached at ~200kph that triggered the ABS in such a manner as to present a confusing set of circumstances the the electronic programming of the ABS controller "which were outside the paramaters for which the programming was created". The flag marshalls reported that the nose of the car dipped as the brakes were applied but once past the bumps, the car's rate of deceleration wsa not maintained. The vehicle impacted head-on into an earth filled tyre bank at relatively undiminished speed (data logging confirmed impact speed of 138kph - at whcih speed the driver suffered unspecified "internal injuries" which were the cause of death - such decsriptions are usual for a ruptured aorta).

There were 3 major consequences of the race incident:
1. Volkswagen withdrew their team from the championships forthwith (and have not re-entered as a distributor backed team in the Production Car championship since that date - and IMHO never will) given (my opinion) the issues associated using an OEM ABS system in a rce environment.
2. The circuit was modified to add large areas of gravel traps to pull cars up before they can impact the barriers, AND the earthen bank barriers have been moved further away from the race-track proper.
3. The sanctioning body removed the previously mandtory requirement for ABS-equipped cars to have the electrical system present in its entirety (which forced entrants to leave the ABS intact), by allowing the ABS to be "removed or disabled" provided that the brake lights must remain functional.

I make this comment only because the only time I have experienced "ice-mode" in my Z34 was at Philip Island on entry to T4 on literally "the perfect lap" where I got T2 and T3 absolutely right and and carried 9kph addiional speed thru T3 and kept the car all the way to the left and ran the left-hand side of the car down the LH edge of the track and hit the same bumps as in the McColl incident - about 12-15m into the braking area). I stood on the brakes - right the the threshold of lock-up, did not initially trigger ABS, but when the LH wheels hit the bumps, it this triggered the ABS and the pedal almost instantly went rock-hard and the ABS "went nuts" but the car did not slow. The situation was resolved by lifting off the brakes and re-applying with a shallow entry/deep trail brake and hard right to recover back onto the circuit when enough speed had washed. This was on the 4th lap of a 5lap run so everything was nice and hot. I run Endless 462TR pads front and rear and Direzza tyres (245/40R18 front and 275/35R18 rear). Pads give good initial bite, tolerate heat, have reasonable CoF and don't chew the rotors to death in road driving.

There is no doubt in my mind that "ice-mode" is an unintended consequence of an OEM requirement arising from the EBD implementation.

Whilst I run my Z34 on the track with VDC off, I have not bothered to disable the ABS but if I were to run the car in open competition (eg: full-on race champioships) then there is no doubt that I'd throw the standard brake setup away, go for ALCON/BREMBO/AP calipers and a stepper-motor driven balance bar assembly.

IMHO, the ABS/EBD logic works OK for the road, but is problematic on the track, and there is lots of good info inthe thread for how to best "manage" it - because that's the price of using a "road-car" in a track situation, the fact that it still needs to serve on "the road".

It is worth noting that the factory GT4 race-car (NISMO Fairlady Z RC) is Bosch MotorSport ABS equipped - details on the NISMO.CO.JP site.

For me, I know I have to stay off the bumps in braking areas on the track, and if not avoidable, I have to ease the brake pressure a little - might cost a tenth inlap times, but that is better than being in the fence.

I have my real race car for serious track work in any event.

Bottom line - everyone who tracks a Z34 needs to be aware of what ice-mode is (and this thread is as good a write-up of what it is I've ever seen) and how to react when it happens, andif serious about their track work, lots of ideas about brake balance that can/will help.

My thanks to the key contributors for an entertaining and informative read - a real gem of a thread ..........

RB