Hi Tom,
It makes me sick, but this will be the first PCA DE event at Sebring I have missed in over 2 years. I am hoping that at the last minute things will work out and we can go. My wife and I drive the Ocean Jade tip TT #01 ("bitch green" as my buddies call it). We are focusing on a trip to Barber Motorsports Park in Alabama July 14/15 for 2 days driving with Chinmotorsports. We have a group of motorhomes/campers going up for the weekend (Brad (Lotus/911TT), Wynn (GT3), Chip (GT3), Dave and Amy (911)). Let me know if anyone wants to join us. Its supposed to be a beautiful track and a great motorcycle/automobile museum.
PS: I am going to leave the PSM on (I don't want to pay for ripping up the manicured grounds or backing through the pretty bushes)

 

Oh, yes, know the car well, another one I cant keep up with!!!! Been meaning to stop by and say hi, I will next time. Lot of my buddies are also going to Barber, I'll be at a NASA race in Carolina.
Well, I'll probably see ya in Sept or Nov at Sebring, good luck!

 

The PSM-thing at the track has been a hot topic for many years in my circles. A part of the problem comes from DSC, the BMW version of PSM. As I understand it, DSC kicks in much sooner, preventing any sort of aggressive driving in a track environment. BMW people mostly manage the track events I attend here in Southern California, and the BMW track-types are very vocal about disabling DSC during track time.

I am in complete disagreement with PSM on the Turbo. It doesn't kick in as soon. I am not a good driver and if PSM is kicking in, I have done something very bad. The Turbo is a very heavy, stable car on a track and I shouldn’t be sliding the thing around corners. At the speeds I’m at (<140MPH or so), PSM does not kick in during tail braking. That being said, I am confused by the comments above about ‘driver assist’. You KNOW when PSM kicks in – the whole car vibrates as the computer takes control stabilizing the car. It isn’t necessary to look down and see of the RED PSM light illuminated. If you don’t feel the shaking, PSM isn’t helping you.

I leave PSM ON, always. If it kicks in during a track session, I need to figure out how to be smoother. MY last track event during the rain at Willow Springs, I didn’t trigger it once.

If you are a good enough driver to erroneously trigger PSM during a track session, you shouldn’t be driving a Turbo – get a GT2/3 or, better yet, haul a REAL track car to the facility.

 

Hi Mike,
I'd be interested in the response of others to the vibrating observtion. I think you can feel it kill the power coming out of a corner, and slows the car if you are about to kick it into an angle. I haven't had a whole lot of vibration that I've noticed.
In other cars, Benz for example, you can't disable it from the seat as the button just changes how much it interracts, not if it interracts. You can tell if you try a countersteer drift, because you can't hold the drift, the car cuts out of it.
In the Porsche, you can definitely tell on or off, but if you are reacting, it just doesn't intrude much. It's just that you cant accelerate as hard, and it slows you more than you dialed in. But vibration... anybody?AS

 

I keep it on... I'm too new to dare try without it. 1-2 seconds won't matter at my stage... I have 5 seconds to improve in other areas like braking, angle of approach, etc. hehe

 

AS, Mike's description I assume is in response to doing something VERY bad in the car, I again would assume a near off road or spin. Luckily, I have never felt that level of interaction Mike. I must admit the most I ever notice is in a high speed sweeper you will sometimes feel a slight touch of pad to rotor, almost a reminder of angle and yaw but the "whole car vibrating" I have never heard of and seems something that may happen at the extreme, maybe.
I think "if you are good enough to trigger PSM during a track session" and you feel it intrusive and not necessary, that would be when I would recommend to turn it off. Selling the car to get a REAL track car may not be necessary. And I think most of us (AS, Lewis, myself, JP) all do have REAL track cars that we trail and even RACE.
Mike, you sound like a better driver than you give yourself credit for because the way I analyze your PSM experience you never feel it and push the car to the very limit and to the edge and then the PSM really kicks fully on to control an agricultural experience!......tom

 

Tom makes a great point. If you can drive on a wet track and not trigger the psm, you're doing something right. I haven't had my tt out in the rain at the track, but every other car I've raced in the rain goes out of shape much quicker, especially when you cross the usual racing line by extending the straights with ultra-late apexing. When i was at Bondurant, I spent about 90 laps in the rain, and cramped my pectoral muscles from all the countersteering. I have never felt that before. If the car had psm, it would have never been silent. (Since their Mustang Cobras don't, I got to see most of the corners thru the side windows.) But driving a tt on track in rain would be expected to trigger psm alot.AS

 

werd. from my track experiences my exact sentiments. if you can trigger the PSM at will during a track sess you are near the limit, unless there is something wrong with PSM and it's interevening too early.

Even if you were to get a GT2 or GT3 and push at the same threshold it will just be a matter of time untill you lose it. Just make sure if you are to push it to the limit there is enough run off.

 

Actually, no. The Turbo is a good (but not great) track car, but it is stellar in wet track conditions. The weight, plus the 4-wheel drive keep the car planted firmly. It is amusing to follow the M3’s at ButtonWillow. The M3’s tail wags all over and the driver seems to be in a continuous fight for stability. The only problem with the Turbo is that water drips in from top left corner of the driver side windoe onto my left leg. (Windows must be open at the events I attend.) I slow down a little and pay more attention to the lines and braking, but PSM is not kicking in. Maybe I’m too conservative?

The only time we see PSM kick in is during braking on uneven pavement.

 

This thread leads me to a broader question: Does anybody know of technical papers describing PSM?
-sensors: Where? What is measured? How?
-physics? Slip angle? Stability models?
-computer? What processor? MIPS?
-throttle? Braking differently at 4 wheels?

I’m not talking about the marketing crap – real technical papers. PSM is cloaked in folklore as to what it does, doesn’t do, and how, so we are all guessing. More technical information would be very helpful to clarify some of these points. While I’m on my soapbox, the ‘N’ crap falls into this category also. Absent a precise technical description of what the definition of ‘N’ is, I continue to assume it is a marketing gimmick without merit.

Note: The apparent power reduction accelerating out of turns is probably the turbos respooling and not PSM. I suspect you let the RPM’s drop too far during braking and the turbos fell out of boost range.

Also, both Turbos I have owned ‘lurch’ a little at 3700RPM, maybe that is what you are feeling?

 

Mike........per your comments on driving in the wet, can I ask what track tires you are running?
I never put slicks or Rs on the 993 and often drove it in the wet...amazed at how much better control I had than other (pretty good) cars.

With the few times I've had to drive the 996 home from the track in the rain (with treadless SportCups) I've pretty much decided to not track the 996TT in the wet. If money was involved I might feel different but I have a hard time enjoying wet on the track anymore.

On the PSM 'technical papers'.......I'm sure you've seen the old Jack Miller artical.....not technical but a good 'no-BS' read pn PSM & the track.

 

As Tom said some of us here run REAL race cars but track the TT as well, personally I track my Turbo when instructing at Porsche events and take my car for fun and some hot laps...

First of all if you're trail braking with effect you MUST have your PSM off as its there exactly to prevent the car from rotating... Please take a look on the RACING sub forum thread where its being discussed under the title: "what a pro driver showed me at the Glen .. opinions?" here's what I wrote:

From my racing experience and instruction my perception is that trail braking is useful on 2 types of cars, rear or mid engined cars and FWD cars that said I must say a properly set up front engined/ RWD car shouldn't benefit from this. I must say that in my limited Porsche tracking experience (I haven't been driving 911's for ages as some of here..) I'm positive that trail braking is only usefull in some types of turns (where you suffer from understeer on the exit from unloaded front axle) but when needed this is HIGHLY beneficial shaving tenth's on each turn but you have to be quick coming on the power again to induce the desired neutral behaviour on the exit. I only mention this on DE's when in the presence of a highly experience group or in the presence of a talented and dedicated individual (after he shows general comfort and ability with car control and advanced techniques such as heel n' toe) as I reckon this can lead to a serious accident.

If you're getting to know a new track or the track is particularly dangerous (very high speed sweepers, walls, etc) then certainly leave it on but for the Pole Position lap time the PSM has to be off although I reckon there should be a quick button at the wheel (as the Ferrari 430) that would unable the PSM quickly and I would turn it off for the slow to medium turns and turn it on again for the long sweepers.

On more thing, PSM is acting upon the car stability and you might not be noticing EVEN WHEN OFF (as it acts when braking) the PSM in not letting you see the mistakes your doing with a potential dangerous side effect which will take place when you drive for instance a GT3 and do some lift off snap oversteer...(Then you hear people saying "there's somethig wrong with this car... it just spun it without notice!) please read another thread on RACING sub forum where ONE rear rotor caught fire w/ PSM off (for correcting stability the whole time)...

 

I generally leave it on.....particularly on larger type tracks. On an autocross course you don't need to worry about it as much because you're the only one generally on the track at the time and you're not going fast enough generally to do real harm. And on a larger track my experience is that when you first go out especially after a long time away from the higher-speed corners you need to re-learn your senses to situations that just don't come up on the street.

I agree with all that is said about smoothness keeping the car out of the PSM.

When mine HAS gone on there is a variety of things that it can do including throttling back.

Just a personal experience; one year ago I took my wife's C4S to Long Beach for the first swap meet they had to replace the old Dunkle Brothers get together. It was raining and exiting the freeway I decided to goose the throttle and have a little fun slide through a corner. Well I must have done it exactly in a grease patch as the car went sideways left very quickly and corrected (over corrected in all liklihood actually) and the tail swung right just as quickly and I nearly lost it again on that side.....this one experience has had me wondering ever since; where was PSM in all of this? I was too busy to notice if the throttle or brakes were modulated besides what I was trying to do. However all this does prove you can spin the little critter even with PSM.

 

Don't run with track tires, and would NEVER run in the rain with slicks. The last day at Willow Springs in the rain was with a new set of Pirelli Pzero's.

The closest I have come to track tires is Michelin Pilot Sport Cup tires. I would never run those things on wet pavement, but thoroughly enjoyed the extra grip on the (dry) track. The wear was too short for day-to-day use, and my local Porsche shop gave me grief for not have ‘N’ rated tires on the car. That is another story …

 

I leave it ON! If I do something stupid it'll let me know, and if I leave if OFF how would I know Seriously, why would anyone want to leave it OFF? If having it ON is good enough for Hurley Haywood, it's good enough for me. And that guy can drive! Very smoothly.