PSM on a 996, what does it actaully do?

I guess what I mean is I've read the manual but I can't work out if it's actually spoiling my fun or not? I can't really detect it doing anything apart from some TC light flshing when I boot it and the grip gets a bit scrabbly. Is it actually cutting power at that point or dabbing brakes??

Both. It uses brakes and cutting power to certain wheels to restore grip. The great Walter Rohrl is only fractionally slower round the 'Ring with PSM on, and reckons most drivers would be quicker with it on. It is one of the best stability control systems, and on the whole allows you a good deal of slippage if it can tell you are 'having fun'. If it senses an unexpected loss of control it cuts in quicker. You can of course switch it off altogether if you think you're 'ard enough...

I don't have it and as yet have not had any 'moments'.

Approach turn (at least 90 degrees) in say 2nd at 2/3'rd rev's Brake to load the nose, turn in, then boot it...... Keep your foot flat and then..... :drive:

What is doesn't do is rewrite the laws of physics - you can still park backwards into a ditch at very high speeds if you want to try hard enough.

what's going on, technically? wheel slip detected, brake applied or power reduced, simple as that?

No throttle applied on manual cars however tiptronics can do. The PSM has yaw meters that allow it to gauge what angle/direction the car is travelling and if it's in a state of under/oversteer apply the brakes individually accordingly. On wet roads/ice the PSM uses ABD (automatic brake differential) and ASR (anti-slip regulation) to maintain stability.

Glad someone brought his topic up. I was driving along the A57 Eastbound on Sunday afternoon, road damp, entered a large roundabout at about 60mph in 4th gear to take a right hand turn. Tail started to slide out to the left and before I knew it, I was perpendicular to the roundabout itself, with the car at a standstill. Spectacular viewing for the onlookers; I was a bit shaken up though as it's the first time this has happened to me. If I'd had PSM, then perhaps this would not have happened. Perhaps if I'd braked enough before entering the roundabout and changed down to 2nd or 3rd I might have avoided this too. ~ Maxie

As Damian said, PSM compares yaw angle with speed and steering angle and makes a decision as to whether you are out of control or not! :hand: If it thinks you are understeering or oversteering excessively (i.e. unlikely to recover based on what you are doing with the throttle and steering wheel) it will firstly take over the throttle control, and then if necessary apply braking to an individual wheel to bring the car back into line / engage the electronic traction control to stop an inside wheel spinning. In a 4WD Porsche, it will also transfer more torque to the front wheels if appropriate - and this feels really WEIRD! :? It's like someone suddenly grabbed the front of the car and yanked it back into line... And Maxie... Yes PSM would have prevented that, but wouldn't have been half as entertaining for the onlookers! :lol:

The best way I found of working out what PSM does was an airfield day, followed by a couple of track days. Gives you a great chance to play around with the car, push it to its limits, and find out when PSM will kick in and correct you. I noticed that with PSM on, track laps feel stiff and constrained and I feel a little like I am fighting the car. With it off, the car is free and feels so much more alive and fun (it also slides more & corners slower which is 100% down to my lack of driving ability). Interestingly, lap times didnt differ much. When I lap with PSM on (1 lap per day max), it kills my brakes. You come back in and they are damn hot even after cool down laps. That is an indication of what PSM thinks of my driving ability... PS - I would never turn PSM off on a normal road, for reasons which I hope are obvious and too lengthy to list.

As someone said above, you can't rewrite the laws of physics with or without PSM !!! :hand:

an article that goes some way to explaining PSM http://www.deter.com/porsche/PSM.txt

PSM - Follow-up from noob - engine lugging with little rain Just purchased my 2002 996 C2 a few weeks back. Roads were a bit damp today - and had a few high speed runs from on-ramp to motorway... Winding it through 2nd, 3rd, then hitting 4th and feeling like the car was lugging only when I hit 4th... A bit unsettling and unpredictable - keeping the accelerator pegged to the floor - it just felt odd. In heavier rain earlier in the day I was overtaking on a small country road and had the same feeling, but much less throttle... Of course, as I learn the car, sometimes I'm simply wondering if that's normal. Driven many BMW 6's and 8's - but the traction control feels very different in them to what I experienced today. I'm hoping this is just PSM figuring out that I'm spinning a back wheel... but it seemed odd to hit 4th gear and have that happen - guess at 5k rpms, it's still trying awfully hard to spin the tires. Also this could all be exacerbated by the new Michelin's with about 150 miles - perhaps they still need to get scrubbed in... A bit of useless anxiety perhaps - :?: - but any confirmation of the slogging/lugging in a straight might be welcome confirmation to me. Cheers -

Welcome 'edoug' :thumbs: Did the orange PSM light flash in the instrument cluster when you felt it 'lugging'? If not, that is not PSM that caused it (or your PSM light is knackered) Excuse my ignorance on specification, but is yours a facelift 996? As, IIRC, only the C4 had PSM as standard on pre-facelift cars, so are you sure you actually have PSM? :? If you have a split coil pack (very common on older 996s) it may be water causing a misfire that is causing the sensation :?:

edoug, I don't think this is PSM kicking in. It is a lot less intrusive than other marques and doesn't come into play until (I believe) you get the back out at about 7% (other systems will come on much earlier than this). Also, when you switch it off, it stays off, unless you brake when the system thinks you're out of control. Could you be a bit more descriptive, is it not putting the power down properly? Does the engine pull smoothly? Wattie is right, you'll see the light flash when it comes on and I've certainly had mine on when accelerating hard in a straight line and go over a bumpy road....but I can feel the rear wheels losing grip when this happens.