DUMB QUESTION REGARDING P.S.M.

Rearrange the letters and you get P.M.S. What is P.S.M.? I failed to order it on my new car -'03 c-2 coupe,powerkit,M030,litronics,sport seats,..you get the picture... Will I kill myself? How important is this and what the hell does it do? Thanks -Blustem

Porsche explains PSM: Porsche Stability Management (PSM), which is standard equipment on all-wheel drive models and optional on the Boxster and two-wheel drive Carrera, is designed to stabilize the car when driver loss of control is impending. PSM (5) uses a number of sensors that provide input to a high-tech control unit. The unit continuously checks and compares input from the sensors to determine the vehicle's direction and movement and how it differs from the direction chosen by the driver based on steering-wheel input. If the system senses (3) that the vehicle is deviating from its proper path while accelerating (1) or coasting � by oversteering or understeering (2)� it takes corrective action by selective braking, throttle change (7), and gear change on Tiptronic equipped models. The Driver Feedback Loop: There is also a Special "driver skill" feedback loop associated with the system. If PSM is activated more often, the system monitors controller activity and wheel speed in order to estimate the thermal load at the brakes. If a preset limit is reached, the system will either modify inputs (e-gas manipulation) or outputs (throttle change), as well as gear change if Tiptronic equipped, in order to slow the car down. What this means is that PSM will give a driver skilled enough to keep PSM activations brief and infrequent the full benefit of normal braking and throttle functions. Conversely, with a driver who continually counts on PSM to save the car from disaster, the system will eventually start to retard power and gear selection rather than using the brake functions. In other words, PSM will reduce available power at the limit. Here the more skillful driver gets more of the car's capabilities. RWD vs. AWD: PSM in rear-wheel drive applications uses different parameters than in all-wheel drive models. True, there is no electronic method of dividing power back to front or side to side in any AWD Porsche (except the 959). However, there is a difference between the two PSM systems. The drive system on an all-wheel drive Porsche (which has more weight up front) relies on momentum to create slip, which therefore increases forward power delivery � and thus the creation of more understeer when compared to a rear wheel drive car. In order to achieve similar handling characteristics, the RWD PSM output functions, such as brake activation times, are slightly different than those of the 911 C4 and Turbo.

Assuming you drive with some degree of sensability, I doubt you will "kill yourself" without it. It is a very valuable feature if you ever push the limits of traction. This includes acceleration. Without PSM you have an open differential and there is no option to order any sort of limited slip. Great if you like to leave one wheel tire marks on the road, but I think not ordering PSM really limits the useable performance capability of the car.

Rear to front torque division.. Have no idea if PSM will do this but on the Toyota Sequoia if both rear wheels slip then the system will apply moderate, modulated braking to the rear this "forcing" engine torque to the front. If the VC is "stiff" enough at the moment to handle the extra torque..... The "ABS vs no ABS" thread has additional info.

What's the "preset limit" that PSM can go on? Is it reset each time the car is started? I've had the light go on a couple of times. Am I possibly losing performance?

You probably had the PSM working too hard or too often. Some systems will shut down because the ABS pump/motor, the heart and soul of PSM, is beginning to overheat.

[quote]Originally posted by Viken: <strong> Porsche explains PSM: Porsche Stability Management (PSM), which is standard equipment on all-wheel drive models and optional on the Boxster and two-wheel drive Carrera, is designed to...</strong><hr></blockquote> Viken, what is the source of this quote? This is the first time I've ever seen anything to suggest that the system might have some "lerning" to it. This doesn't exactly sound like learning but it does sound like adabtability of a sort. Also notable that the system seems to start life giving full authority to the driver and then take it away. You would think a truely adaptable system would work in the other direction. Guess it is more about preserving the system than the driver. But interesting nonetheless. S.

I asked my Porsche service manager about the PSM system "learning" and "remembering". He says that it has some "fuzzy logic" that is used to provide some minor anticipation but also said it would be very minor and not really noticible. Certainly not to "slow down" the car after you try breaking the wheels loose in rapid succession. More like a millisecond earlier in a break loose sideways movement. He says he would be amazed if anyone could really tell because the system is so fast anyways - I can attest to that. And if you turn it off, it is not remembering or fuzzy or anything. Keep on flashing...

[quote]Originally posted by FixedWing: <strong>Viken, what is the source of this quote? This is the first time I've ever seen anything to suggest that the system might have some "lerning" to it. This doesn't exactly sound like learning but it does sound like adabtability of a sort....</strong><hr></blockquote> Didn't I type above that this came from Porsche? Why, you don't trust them either?