ronmart

BTW, MJones - I saw the GT3 ad again in the Porsche Travel Club 2006 Brochure and apparently the Masters Course in Germany uses GT3's.

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have you ever seen your psm light come on?
i slide every day and have yet to get that thing to light!
maybe mines broke?

ronmart

In every day driving with the sports button on, no. I've done 4 wheel drifts and haven't seen it come on.

With the sports button off on regular streets, I've only seen it come on once when someone else was driving my car.

At the skills event I saw it come on a few times, especially on the autocross and skidpad, but it felt like an entirely different car with it off because I was actually able to drift the rear end when it was switched off.

BiggerTwin

I don't know what PDE policy is but at Skip Barber you are responsible for $10,000 in damage if you crash a car. For another $100 you can reduce your exposure to something like $2,000. At these prices, especially in the wet, I had no problem with PSM.

Alan

MJones

On track PSM is always ON, the button is disabled...PSM on the 997 has a wider slip angle than did the 996. If all of your inputs are right there is no PSM intervention, you wont even know that you have it.
The car will rotate nicely in 5 and 14...no intervention. I did get a PSM flicker cresting the t4 hill at a bit over 90mph, and it's a known area since the car gets really light and the tires actually spin.

On the figure 8 Skid Pad (no grip, like black ice) PSM is off to practice car control and vision.

I've been behind someone who went a bit wide exiting 8a and it saved him...without it would not have been pretty. There was someone who did a big spin across the track after 4 who was off line and tried to bring it off the grass. There was a guy who went wide at the tunnel turn, two wheels off, tried to bring it back, spun across the track and buried the nose in the tire wall and put a wrinkle in the roof of the 997. I was in attendance for all of the above incidents.
PSM will not get in your way if all of your inputs are correct..Does not get in my way nor in the way of drivers doing hot laps.
Why would you want to turn it off ???


The PSM parameter (Slip Angle) is actually quite wide..
PSM deliberately waits until the last moment to intervene, particularly at low speeds of up to around 70 km/h / 45 mph, enabling more agile driving behaviour in tight corners.

There is only one corner turn 5, hairpin where you are in the mid 40mph range. Watching people go thru that corner the spoiler for most retracts which indicate a speed of <37mph ....Exiting the bottom of the Museum complex (7, 7a, 7b) is another slow area for alot.

You gotta drive Barber to appreciate never resting and technical it is. Not really Hi-speed in the MPH sense but Hi-speed in how you navigate it's undulating corner complexes.

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was hoping mjones would input his knowledge!
this was the best description i could find on the way psm works:

Recognizing that even street drivers expect excitement from their
Porsches, PSM allows approximately seven percent slip angle before
intervening. Five to seven percent is generally agreed to be the limit
for modern, high performance tires. The biggest difference between PSM
and the other systems on the market today (Mercedes Benz, BMW, Jaguar,
etc.) is that PSM is programmed to allow a good deal of slip, as you can
see. All of these other systems clamp down the moment any slip (i.e., fun
driving) is detected.
We wanted the car to perform like a Porsche not a family saloon, so the
system has been designed for minimal intrusion," explained Thomas Herold,
the Carrera 4 Project Manager. "Its limits are really high and you can
reach the same lateral g-force number with the system in or out on a
steady state cornering circle. Thus, if you are a good driver, you can
keep the power on in a drift and even adjust the car’s attitude on power
in a corner without interference. But if you lift off suddenly or brake,
and the car is in danger of destabilizing, the system will reach out and
save you.
If you are smooth, there is no interference from the
system. But if you are ragged, the system will be cutting in all the time
to stabilize the car".
even when turned off to ensure your safety, PSM remains present in the
background and will only intervene under heavy braking where at least
one front wheel requires ABS assistance

i'm sure ive gone over 7% though and it hasn't intervened.
maybe because the speed wasnt over the threshold needed
or because i stayed on the throttle?

see ron! you just have to smooth out that ragged driving of yours!

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damn! we need to complain if that's true!!!
only problem is if they switch to gt3's for masters at barbers all you guys
are gonna wanna trade for one after taking the class!

MJones

ICON ...Great find...and it is so true..
If it comes on your overdriving the car.

I've been on many crazy "Hot Laps at Barber" and there is NO intervention.

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thanks brian!
i should have mentioned the text came from
"A racer’s perspective By Jack Miller"

allegretto

I have to admit to confusion here. What is a "7%" slip angle? I understand slip angle and yaw, but 7% of what specifically? I'm used to these in units of degrees, not %-ages.

What I mean is, is it saying that the numerator is the difference between wheel axis and vehicle axis and the denominator is...?

Or...?

MJones

Slip angle of a tire:
Definition: The angular difference between the direction in which a tire is rolling and the plane of its wheel. Slip angle is caused by deflections in the tire's sidewall and tread during cornering. A linear relationship between slip angles and cornering forces indicates an easily controllable tire.

My PSM % slip angle theory:
Since PSM monitors many perameters ABS sensors (which measure the speed of each wheel), engine speed (RPM), throttle position (via E-Gas), gear selection, lateral acceleration (side to side), yaw (the car spinning in a circle), and steering wheel position.
Perhaps the computer is caculating an imaginary "friction circle" where a % of limit is more appropriate than a specific degree of angle given all the perameters monitored.
You are within or exceed a % of total perameters of the PSM algorithm

PSM can not monitor "Grip"

Interesting that on the PDE skid pad with PSM ON if you are very very delicate with your inputs you can drift the car slightly, but it is so hard since you are on "black ice" conditions with no grip but is achievable for short periods.

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but what is a 100% slip angle for reference? 90 degrees or 180 degrees?

OCBen

I would guess that slip angle is always an acute angle and not an obtuse one. So I'd say 90 degrees is your 100% slip angle.

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is that what you tell your boss? "i would guess"

OCBen

Sorry Boss.
Let me rephrase that for you. ... "In all probability..."