mcbit

I think that it depends on a whole bunch of values rather than on a single parameter.

horsepowerfarm

These two posts are quite accurate, except that acceleration and deceleration are included with slip angle.
I have driven mine over 80,000 miles with PSM off except in the rain, and some times I turn it off in the wet for fun. This car is my 24th 911 variant I have owned (4 were 930's) over the last 44 years. I'm pretty comfortable in them.

993GT

IMO, 996 gen PSM was a good step above everyone else's systems at the time, but technology/technique has improved with time..
again, IMO, 996 PSM allows a fair bit of slip angle before correction, but the correlation between active/passive vs grip/slip is too wide; to say the PSM system should be acting sooner with more progression as slip angle/yaw increases.
I don't want to sound GT2 biased vs TT, but I prefer not having PSM as it somewhat adds a false self-confidence that really shouldn't be there in a performance/hard-driven car. If you've really misjudged/messed-up, PSM MIGHT save a spin, but will be slop-show doing so...a 911 with a proper LSD has the confidence and stability needed to be quick without undue effort...

"02996ttx50

i've always enjoyed their marketing info.

"Porsche equips the 2002 911 Turbo wîth the Porsche Stability Management system (PSM), an innovation the automaker first introduced on the 1999 911 Carrera 4. Úsing data from several sensor inputs, PSM can detect a loss of grip at the front or rear and reduce instability by applying braking to individual wheels and, if necessary, altering engine power. PSM can help keep the 911 Turbo going in the direction the driver steers, especially on slippery roads."

and my other favorite part:

"The PSM system operates so quickly that most drivers likely will not feel it making corrections,"

jumper5836

PSM does a great job of saving you and keeping the car from going off the track fast and rear first. The LSD can and will lock up a rear tire if it spins more quickly then the other side rear tire and it sends more power to the other tire which will cause the the car to spin around so quick its not funny . Believe me i know, done it in the heavy rain under acceleration and was facing backups going 100kph. This is where all wheel drive and individual wheel braking would have kept the car going straight by sending power to front wheels and then braking the spinning wheel. This would have kept the car from spinning.

The more modern 991 PSM is way better though and even works great on non awd 911's, like you've said this is due to better and more gradual progressive control of the 4 corners and what the sensors are reading where as the 996 PSM is crude and intrusive and seem to have no progressive control at all.

487

PSM off on track so it will slide, leave on for street driving.

Smoltz

I am a beginner track driver, did half a dozen or so events with 996TT. PSM On. It has saved me a few times from either a spin or from me having to perform heroics that might have been beyond my skills.

PSM allows a fair amount of rotation before intervening. In my experience enough time to say 'oh ****' and then you see the light and you can breathe. There were a few spots on a few tracks where I felt like it was doing more harm than good or would do something unnecessary but I was usually able to mitigate that and never felt like turning it off would have been worth it.

Compared to my E46 M3's DSC system, PSM is FAR less intrusive.

If I had a trailer for my car and was planning on going racing, maybe I'd go PSM off, but I drive my car to the track and want to be able to drive it home.

"02996ttx50

well, compared to my fwd mildly modded gti the dsc is a lot more intrusive than the psm is in my 96t but i have HAD it with its intrusion into my driving. as i've said, has it "bailed me out "before"? yeah, probably, and once famously when i was in WAY over my head. but i now feel it as more of an intrusive and highly disconcerting complement or impedance ( pick one ) to my spirited driving. but then, i think i "know" the car, and my own limits in it far better also, after these several years. it's a helpful learning/teaching aid as it steps in often before you even knew you NEEDED it to. is how i've come to see it, and something that many outgrow. inclement weather notwithstanding. that's a whole different story. psm and snow/sleet/ice et al coupled with awd! seem like a perfectly reasonable and well considered combo.

but i'm never IN THAT stuff.