Tom Tweed

If you read the article in the June '07 issue of Excellence regarding the building of Synergy Racing's 997CP cars for the Grand-Am GS class, you will see how true this is. The PSM is so fully integrated into the electronic control of the car that it is nearly impossible to disable it totally. Some quotes:
"PSM is beyond complicated: If you touch something, it's like cracking a piece of glass. It just goes in different, unexpected directions."
"Synergy devised mechanisms to mask driver inputs from the system."

From their experiences, it appears that updating the ABS system was required, as well as mechanisms to mask jerky inputs and concurrent throttle and braking inputs, among other things not fully disclosed (probably), to prevent PSM from intervening in detrimental ways in the street 997 under full racing conditions.

They seem to have succeeded fairly well, considering their record in Grand-Am, and the fact that Patrick Long was able to drive one of their 997S cars within 2.5 seconds of a GT3 Cup in a lapping session at VIR.

TT

mdrums

Yes that Excellence article about Synergy is very good. For those racers that want to totally disable PSM I still do not understand why they can not just take it completely out of the car when they gut the car. Somebody in today's age can surely re-program/hack the computer to remove PSM.

Joe Weinstein

I am a long-time serious competitive autocrosser, currently with a 996tt.
To win at autocross it requires absolutely 10/10ths of the car and driver
for the entire 1-minute run, in the most transient and dynamic chassis conditions.
Unless I am racing with slicks in very wet conditions, PSM must be turned off. It
can slow the car by a second in a 60-second lap. I have had it actually shut off the
power for a second during a needfully sharp move. For precise and at-the-limit
zig-zagging, it can interrupt like a lawyer tapping your shoulder while you're having sex.
Joe Weinstein

http://www.sfrscca.org/solo2/Results...nship/asp.html

RonCT

We were talking about road racing. I can easily see how PSM could get in the way of autocross...

cviles

The problem is just how many systems are integrated to make PSM work. And if you any of those components are removed, the computers throw a fit. PSM works with the ABS sensors, the ABS pump, the yaw sensors, sensors for the steering angle and throttle position, the DME to retard engine power when necessary etc. And these are just the ones off the top of my head. I'm sure there's a separate module tied in to all of this that runs the instrument panel and flashes the light at you...

JC in NY

Isn't the PSM computer designed to correct the car when it is outside of it's optimum performance envelope (primarily yaw angle) by using the rear brakes?

So, if a skilled pilot is using the car most effectively, it would stand to reason that it can be left on always even when setting a record lap.

Joe Weinstein

It depends on what the driver is trying to do. The bigger and more separate
the turns are, the more likely it is that PSM would not intrude on a good
driver. In autocross, where you may have to go from absolute max left Gs
to absolute max right Gs, and back again within 100 feet, PSM does over-slow
the car, and winning drivers get through faster and cleanly without it. In other
words, the optimum performance envelope is perhaps too complex in the
general picture for PSM to know, though it does well in the simpler cases.
And PSM does not only operate by applying brakes. It can also shut off the
throttle. Autocross driving is too wild (from the perspective of high and
rapidly changing G-force inputs) for PSM to accomodate. Autocross is
orchestrated instability at a degree that the risks are too high to ever rely on
at higher speeds, and are unnecessary on race tracks except in emergencies
like avoiding flying cars and debris, and those are instances when even in a race,
stability temporarily trumps max performance.
Joe W.