How Does PSM Work

[guyh]

Interested in how it works, in particular does it apply brakes, so on a track day will you get undue brake wear if you don't switch off PSM ? (I have a Gen 2 Cayman S)

Guy

[SaucyBoy]

Here's an explanation by 996alott on the first page (Refers to the 996 turbo)

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[daveyb662]

Thanks Saucy for that link.

Made interesting reading. Good info!

[spyderman8]

It can certainly result in extra brake wear on track and I believe Porsche even recommend turning it off on the 997.1 GT3. I did a gymkhana recently at Millbrook and had to turn it off - intervened far too much to allow proper control of my 986. Haven't yet turned it off on track though - should have last time I was at Silverstone - just don't have enough balls to yet!

[guyh]

Break wear on my gen2 Cayman S has been higher than I would expect and this maybe why. My first track day was at a wet Bedford and the PSM constantly cut in to spoil fun, I do trail brake too so guess that's not helping.

Guy

[daveyb662]

spyderman8 said:

It can certainly result in extra brake wear on track and I believe Porsche even recommend turning it off on the 997.1 GT3. I did a gymkhana recently at Millbrook and had to turn it off - intervened far too much to allow proper control of my 986. Haven't yet turned it off on track though - should have last time I was at Silverstone - just don't have enough balls to yet!

Is gymkhana a good way to explore the limits of your car?
I would be interested in doing this. Any more info? Did a quick Google, but seems they related to driving a Caterham rather than your own car...

[spyderman8]

daveyb662 said:

Is gymkhana a good way to explore the limits of your car?

I did it with CAT Driver Training at Millbook in Bedfordshire. You are correct - they really want you to use their Caterhams - which I hated. They let my use my Boxster instead, but to be honest I'm not interested in deliberately losing grip - more finding where the grip limit is and still maintain control. It was still interesting trying to fling my Boxster round cones on a concrete surface. Poor tyres!

http://www.catdrivertraining.co.uk/

Edited by spyderman8 on Tuesday 27th December 23:09

[daveyb662]

Thanks for the info...I much like yourself want to explore the limits - not jus deliberately lose grip.

I will contact them and discuss options.

So is the surface bad on the tyres? I have jus recently had all four done so that may be a bit of a put-off if I am honest!!

Thanks again.

[spyderman8]

I dont blame you - I had new tyres at the beginning of this year too!

The pad they use is concrete so it's not as bad as Tarmac I believe. They do courses far more suitable for our needs at Bruntingthorpe and they can be done in their Subaru Imprezza or Boxster - TBH that's what I should have done in the first place.

[Pope]

PSM is not one system; it incorporates the following:

ABS - Anti-Lock Brake
ABD - Automatic Brake Differential
ASR - Anti-Slip Regulation
EBD - Electronic Brake Force Distribution
EDTC - Engine Drag Torque Control
DOA - Drive-Off Assistant
MBU - Engine Brake Torque Assistance
SC - Stability Control
TC - Traction Control

and in later vehicles:

EBR - Enhanced Braking Readiness
EBA - Emergency Brake Assist

The ABD is responsible for pushing drive across the axle away from a spinning wheel to the one with the most grip - electromechanically mimicking a conventional mechanical LSD - In the case of a Cayman this will be braking the (spinning)rear wheel during hard acceleration in order to minimise wheelspin along with control over the engine performance VDC/EDTC/MBU/ASR (throttle position, fuelling and ignition timing) and is where the brake wear appears. The PSM has full control over the throttle valve as well as the braking system and if necessary can over-ride the driver's inputs to maintain stability.

Trail braking into a corner loads the front for a better turn in but may decrease the available grip at the rear when the power is reapplied - giving the ABD and associated systems more work to do.

Essentially PSM is allowing any driver to extract the most from the dynamics available in a given situation, switching it off or removing it altogether leaves it all down to the driver and his/her skill.

The SC/TC system on GT3's is far less involved with the handling side compared to PSM concentrating mostly on torque application without loss of traction - predominantly by applying the rear brakes.

Worth noting that Porsches 'Ring time was only 3 seconds faster PSM OFF

PSM explanation here (early system, now on PSM9.0+
www.usuarios.multimania.es/cporschecat/angles/tecn...

HTH

Edited by Pope on Wednesday 28th December 16:31

[monthefish]

More info here.

[daveyb662]

spyderman8 said:

I dont blame you - I had new tyres at the beginning of this year too!

The pad they use is concrete so it's not as bad as Tarmac I believe. They do courses far more suitable for our needs at Bruntingthorpe and they can be done in their Subaru Imprezza or Boxster - TBH that's what I should have done in the first place.

Just called Bruntingthorpe, they allow you open time on the circuits at a very good rate, so may well consider going down some day soon...now just need to find some insurance!!

[doneitnow]

spyderman8 said:

I dont blame you - I had new tyres at the beginning of this year too!

The pad they use is concrete so it's not as bad as Tarmac I believe. They do courses far more suitable for our needs at Bruntingthorpe and they can be done in their Subaru Imprezza or Boxster - TBH that's what I should have done in the first place.

Isn't Concrete worse for wear on tyres than Tarmac?

[threesixty]

spyderman8 said:

It can certainly result in extra brake wear on track and I believe Porsche even recommend turning it off on the 997.1 GT3. I did a gymkhana recently at Millbrook and had to turn it off - intervened far too much to allow proper control of my 986. Haven't yet turned it off on track though - should have last time I was at Silverstone - just don't have enough balls to yet!

997.1 gt3 doesn't have psm?

[Trev450]

doneitnow said:

Isn't Concrete worse for wear on tyres than Tarmac?

Its much more abrasive so I would say so definately.

[911p]

daveyb662 said:

Thanks for the info...I much like yourself want to explore the limits - not jus deliberately lose grip.

I will contact them and discuss options.

So is the surface bad on the tyres? I have jus recently had all four done so that may be a bit of a put-off if I am honest!!

Thanks again.

The surface at Millbrook isn't bad on the tyres at all, the whole place was built to mimmick actual road surfaces, and we barely lost any tread when we did a CAT DT course there recently. It's not an aggressive surface such as at Bruntingthorpe which will destroy your tyres; in fact CAT DT won't even let you use your own car at places where your tyres will lose significant tread.

[spyderman8]

threesixty said:

997.1 gt3 doesn't have psm?

Sorry - you are correct - only has TC. Was probably thinking of the SC & TC features on the Gen.2 that can be switched individually.

[Sunnysidebb]

I did a full afternoon at Bruntingthorpe with Ken, Toby, Steve and a few others in November. Weather was fine and track dry. I was out pretty much most of the time topping 200 mph at times. I did many laps hitting over 195 on the long straight and 150 on the short straight. I was taking Boeing 747 bend at over 100 mph. Anyway just to show I wansn't hanging around. I started with 2 new rear tyres and 2 almost new fronts. I finished the day with at least 50% remaining. I was very surprised and delighted to find i had some tyres left at all. The 911tt drifts beautifully at 100.lol

[monthefish]

911p said:

we did a CAT DT course there recently.

Did you get much from it?

[911p]

monthefish said:

Did you get much from it?

Pick up this months Total 911 I did a whole two page writeup on it. Page 86.