I'm not talking about my wife! I recently bought a Y2K 996 C2 coupe and am loving learning to drive it. It is much more technique sensitive than my C5 Vette. Much freer revving, much more difficult to do perfectly smooth upshifts and, especially, downshifts. Yesterday I was turning onto an entry ramp and got on it pretty good. Got the tail out a little and thoroughly enjoyed it. I had the PSM in the engaged position. After reading a little more about the PSM in the owners amnual and on the web, I think I have gleaned that the PSM is more active under braking. But I am still not sure how invasive it is likely to be. Should the PSM have prevented the loose tail feeling? Just what are the practical limits of spirited motoring with the PSM engaged?

Any references would be appreciated.

 

A quote from a review of the 2000 C4, your model year:

"In addition to the all-wheel-drive system, every 911 C4 comes standard with Porsche's Stability Management system (PSM). Using data from multiple sensors, PSM can detect a loss of grip at any wheel and apply braking and/or reduce engine power to reduce instability. The system is designed to keep the car moving in the same direction that the driver steers on slippery surfaces, while lending a "helping hand" during enthusiastic driving on dry surfaces. We never experienced either situation on Mulholland, both because it wasn't raining and because we don't try to find a sports car's limits on public roads. However, we did confirm that, even with all four wheels receiving power, the 911's tail could be rotated just enough to give the car a rear-wheel drive feel. This delighted those of us who appreciate the security of all-wheel drive, but love the thought of gently rotating the car through a corner apex. Not many carmakers can offer both traits in a single vehicle...but Porsche can. Even more exciting was that this slight amount of mischief was allowed even with PSM turned on, giving you at once the thrill of oversteer and the peace-of-mind of stability control. When it comes to dialing in the this hi-tech nanny, Porsche got it right!"

There are a variety of sources dicussing PSM. I thought the above quote answers your specific question. More recent discussions seem to indicate that the PSM is more than brake modulating and reducing power to a particular wheel. It is not simply an anti-lock mechanism. It also increases or redistributes power to the needed wheel(s) to get the car going where it should go. I don't know if this is a delayed realization or it is an improvement on the earlier PSM's. In my experience, I actually heard rather than felt the rapid staccato of the brakes modulating on one corner where I became uncertain and lifted. As soon as I regained my composure and pressed on, the car actually felt like it launched itself around the final curve and into the the straightway. Without PSM, I may have plowed off the curve. Quite a confidence builder. Been nailing that throttle earlier in the curve since. The car literally pulls itself around that corner. A real rush.

Enjoy the car. Attend some DE's. I have no idea where the practical limits are. I can, however, tell you that I have reached the limits of my courage, and the car and PSM seem willing to go way beyond that.

 

"But I am still not sure how invasive it is likely to be. Should the PSM have prevented the loose tail feeling? Just what are the practical limits of spirited motoring with the PSM engaged?"

It's one of the least invasive system in production by any manufacturer. Only Corvette's system is supposed to be as good or better at correcting without taking the car away from you. I get loose tail every so often as well with no PSM. Major tail requires it to be turned off though. That said, the system is supposed to be capable of "learning" the driver. Hence, mine has come on progressively later the longer I've had the car (guess this is because I find PSM more than most). Many will suggest that perhaps I'm becomming a better driver and not getting the car out of balance to the point PSM is programmed to assist. However, I don't think that's the case. Rather, it's probably a little bit of both. That said, perhaps the guy who owned your car before you, "taught" the PSM a thing or two :-)

And yes, the system is a WHOLE LOT more than just braking! FWIW, after putting on a stiffer suspension, I've actually had PSM come on going over dips at higher speed (especially while cornerning).

 

[quote]Originally posted by ben in lj:
<strong>Only Corvette's system is supposed to be as good or better at correcting without taking the car away from you.</strong><hr></blockquote>

Hey Ben,

That's not right. The Corvette's Active Handling SUCKS compared to PSM. The Vette's AH system is very instrusive. I'm not fond of PSM, but I hate AH.

 

I love PSM. I used to do Run what you Brung racing back in my HS and college days. Had a ricer (Yes, I confess. I had a ricer. Don't beat me anymore. <img src="graemlins/crying.gif" border="0" alt="[crying]" /> ). No PSM, no ABS.Bare bones, bare knuckles kind of thing. Tail out cornering, tail wagging, four wheel drifts, entering corners sideways, 180's, 360's. They are all fun, and can be done today when you turn the PSM off. But, they don't increase your speed nor decrease your lap time. PSM is not just a safety net, it is also a performance enhancement. I put it in the same category as sticky racing tires, competition suspension, racing brakes. On the C4S and 996TT, it directs a significant amount of the considerable power to the appropriate wheel to take you quickly around turns. PSM, together with the viscous coupling of the AWD, is what directs up to 40% of the power, not just to the front wheels, but to a specific front wheel. This puts the cars on rails in almost any situation.

In spirited driving, the PSM is so unobtrusive that you don't know it's there. If you are a relatively weaker driver, you will utilize the brake modulating safety net function mostly. The better the driver, the more the performance enhancing function comes out. I believe the PSM goes on in almost every spirited corner one takes. One just doesn't know it.

If it sound like I am enamored with PSM and C4S, I am. I have embraced it. I have just broken the 2000 mile mark on my new C4S, and have claimed a 5 mile segment of twisty mountain road. Several times. This is the benchmark experience to which all my future driving experiences and cars will be compared to. I can't even find the appropriate smiley or Instant Graemlin for it.

 

there are two versions of Corvette Active Handling. '98-00 cars would pull back engine timing first ( like Mercedes ). '01 - '02 cars engage brakes first. The latter is better for enthusiasts. The former saves your brakes if you are driving in slippery / snowy conditions. Chevy answered the gripes from it's Corvette owners who said they have another car when it's snowing ! You also have the option of yaw/TC , yaw only, full off with the C5 system. Porsche system you can never turn off completely, which frustrates some hard core racers.