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    PSM advice

    I have had the back end of my 997S wander three times now, not so that I saw the world through my side window but I certainly had to steer into the skid. Clearly all my fault, accelerating too quickly out of sharp bends, fairly low temperatures (c3 degrees celsius) on summer tyres and mildly damp roads.
    What surprised me was that there was no intervention by the PSM, I caught it all three times, after the first two I wondered if the PSM had activated and I had not noticed, but tonight I am in no doubt it did not intervene. Is this because things had not got bad enough, ie the angle was not great enough? or should I have the dealer check.
    What sort of action is going on before the PSM takes charge?
    (I have RTFM gives only general advice, and it was certainly on all three times)

    Re: PSM advice

    Not sure but were you in sport mode? That may have delayed PSM activation.

    Re: PSM advice

    I have PASM rather then -20mm but I was not in sport mode,

    Re: PSM advice

    I had to go an empty lot and force it to work. Otherwise, the tail breaks all of the time at low speeds. I'm a little afraid to push it going fast, fearing that I may not catch it. But, I shouldn't be doing that sort of stuff on the streets anyway.

    jb

    Re: PSM advice

    If you are wondering if PSM is working, just do a standing start on a wet road and see if the PSM light flashes and the throttle gets cut off by the PSM when the rear starts to skid. Its very noticeable in that situation.

    PSM allows something like 7% tire slip before it activates in normal mode so either it wasn't enough to activate it or it was very smooth when it can on (can happen depending on the situation and what PSM has to do) and you didn't notice its action. PSM isnot only more permisive but also very smooth compared to BMW's DCS or MB's ESP.

    Re: PSM advice

    If PSM determined sliding would be a faster solution out of that corner, it would have allowed it as long as the steering was pointed to the direction you wanted to go. Try to remember whether the front brake of the outer side wheel induced you to counter steer when you caught the rear.

    Re: PSM advice

    I've had very similar experience myself with my new S. I must admit the first time it caught me out was on a damp road when I floored it in second gear. What caught me out was that I was pointing fairly straight but the back end stepped out by quite a bit. I was in 'sport' mode and I feel I caught it before PSM stepped because I lifted slightly aswell. Must admit I had to check my trousers afterwards - it was a narrow road

    I used to have a C4S and in that you could just floor it anywhere and it would just grip and go. I suppose with more power and rear wheel drive I will have to be a bit more respectful of the S!

    It's funny you posted this - I was going to post exactly the same thing tonight aswell!

    Wolvy

    Re: PSM advice

    The Drivers in the "Porsche Driving Experience" say that a 30 degree slip angle is allowed before PSM intervetion in Sport
    mode. Even in normal mode, the car has to be pretty out of shape before activation. That's why we all accept it ;
    as enthusiasts. Revvv

    Re: PSM advice

    Quote:
    Revvv said:
    The Drivers in the "Porsche Driving Experience" say that a 30 degree slip angle is allowed before PSM intervetion in Sport
    mode. Even in normal mode, the car has to be pretty out of shape before activation. That's why we all accept it ;
    as enthusiasts. Revvv



    When did you last attend PDE?
    Were there 997's?

    Re: PSM advice

    Quote:
    Revvv said:
    The Drivers in the "Porsche Driving Experience" say that a 30 degree slip angle is allowed before PSM intervetion in Sport
    mode. Even in normal mode, the car has to be pretty out of shape before activation. That's why we all accept it ;
    as enthusiasts. Revvv



    A slip angle of 30*? that seems quite a bit slip angles would be the limit for cornering. I also heard the 7% "tire slip" figure which would reffer instead to the limit of longitudinal slip of the tire it allows I guess such as in a standing start. Frankly I love how Porsche has designed the PSM, its just as should be for street driving.

    Re: PSM advice

    OK guys thanks for the help, I obviously didn't go far enough, there's always next time!

    Please Save Me!

    It's a wonderful thing that it allows you to play beyond or close to beyond your capabilities yet will bring the car back for you when you have an "Oh...SH*T!" moment.

    With Sport Chrono set on sport and a damp surface and cold tires it can be a lot of fun. It's one of the reasons why I got rid of the C4S and I'm on the "waiter" list for a 997S.

    Re: Please Save Me!

    Quote:
    Le Chef said:
    It's a wonderful thing that it allows you to play beyond or close to beyond your capabilities yet will bring the car back for you when you have an "Oh...SH*T!" moment.



    I agree that PSM is essential. Bear in mind though, that PSM will not always save your bacon. It cannot violate the laws of physics. In slippery, low traction, conditions the car may go out of control, PSM or not.

    Re: Please Save Me!

    Forgive my ignorance, but some of you talk about PSM as a device that "reads" where youre supposed to be going in terms of direction, others describe it as intervening when a tire is 7% out of sync...or something.
    Can anyone explain to me exactly what PSM does? (Other than the antispin-thingy)
    I have it on my measely Boxster S, and it seems to allow me about a meter (3 feet) of slide in a corner before it steps in.
    How much that is in terms of percent I dunno, but it seems to be working just fine.
    What John a describes sounds like a VERY laidback safety precaution...one that almost isnt worth a lot in the real world?
    I mean...who needs it, if you have to catch an unintended slide yourself?
    Sounds like only John's routine and cat-like reflexes saved him from ending up in some exotic place with his car.

    I mean, a slide or broadside can only happen if you steer and either accellerate too fast or decellerate too fast at the same time.
    How PSM would counter the latter, I dont know, but it should be a fairly easy task for the electronics to reduce accel. and thus avoid the slide.

    Re: Please Save Me!

    Quote:
    DrPhil said:
    Forgive my ignorance, but some of you talk about PSM as a device that "reads" where youre supposed to be going in terms of direction, others describe it as intervening when a tire is 7% out of sync...or something.
    Can anyone explain to me exactly what PSM does? (Other than the antispin-thingy)


    Here is the offical link
    Quote:

    I mean...who needs it, if you have to catch an unintended slide yourself?


    because people complainted PSM come in to early in 996 reducing the fun.

    Re: PSM advice

    Quote:
    Revvv said:
    The Drivers in the "Porsche Driving Experience" say that a 30 degree slip angle is allowed before PSM intervetion in Sport mode.


    Are you really talking about slip angle? Because 30 degree seems a lot.

    Here is the definition of slip angle.
    Slip angle is a term used to describe a particular type of flex in tires. Slip angle is a measurement of how much the tire's contact patch has twisted in relation to the wheel. NOT the different between tire and car direction.

    Re: PSM advice

    It is the fact that you counter-steered which caused the PSM not to intervene. Had you failed to counter-steer then it would have intervened. The system is looking at your steering angle and comparing it to the yaw rate of the car. You steered into the slide which told the system that the back was basically going where you wanted it to go. Had the rotation continued unchecked then it would have intervened.

    Basically, the system will allow a competent driver to do reasonable things. Even in my 996 Turbo I was able to leave it on at the Nürburgring and the only time I would see the PSM light was when a wheel got airborne and somehow confused the system. Even then it would only rarely intervene in any sort of big way.

    I will also bet that your slides were at slower speeds. At higher speeds, where you tend to counter-steer less, and where the rate of rotation can be higher, I think you will find the PSM being more active. That's my experience anyway.

    Porsches system on the newer cars (starting with my 996 Trubo) is in my opinion just incredible. Other cars force the driver to turn the stability system off to have any fun. Porsche allows it to remain on. This is ultimately safer as you still have some sort of safety net if things do go terribly wrong.

    I also like that the new sport system has varying degrees of aggressiveness which are driver adjustable. This means that it one can still count on the car to intervene early on a dark wet night when a deer runs in front of you. My presumption is that there is occaisionally going to be a price to pay for really late intervention so that early intervention should be favoured unless trying to drive aggressively.

    Definitely one of the best parts of a Porsche these days. So when are we going to see it on the GT2/GT3 series?

    Stephen

    Re: PSM advice

    John A i am wondering if your PSM is working properly as i have only had my C2S for 1 week ,done 100 miles, and have noticed the PSM light flashing up on a number of occasions already.Like Carlos said if you floor it from a stand still in damp conditions you should get enough spin to bring on the PSM light.
    I must say this car must be treated with respect as i have also had the back swing out on me,i had switched the PSM off and beleive me it makes a difference The car is awesome and i love the fact that you can get the back out but i will now respect my C2S just that little bit more

    Re: PSM advice

    I've been getting the back out in mine a little bit when it's safe to do so. It's been raining quite a lot here recently and I love just dabbing the throttle a little more than I should to provoke a bit of tail wagging. I thought the PSM was quite noticable even with Sport Chrono selected.

    Re: PSM advice

    Introducing the new 911 Carrera and Carrera S, Porsche also hails the advent of a new generation of Porsche Stability Management (PSM). In terms of both longitudinal and lateral dynamics, PSM ensures a very high standard of active safety when driving to the extreme now combined with even greater agility and driving pleasure so typical of the brand. The new tyres, further refined control quality, and optimised ABS components also serve in this context to make stopping distances even shorter than before. New ABS sensors offer the input for this superior management and control, determining wheel rotation no longer by conventional pulse wheels, but rather by multi-pole seals fitted directly on the wheel bearings. The improved signal obtained in this way can now be used for more precise processing and control purposes, linear solenoid valves serving to adjust brake pressure with almost infinite precision, that is much more precise than with conventional shaft valves. This the driver will feel, inter alia, by the reduced pulsation of the pedal when applying brakes in the ABS mode. This greater performance is matched by an appropriate decrease in weight, a new hydraulic pump serving to build up the brake pressure required so quickly that the system no longer needs a pre-charging pump with all its connections, which reduces system weight by 3 kilos or 25 percent.

    To ensure even more agile handling and behaviour in bends, PSM intentionally intervenes at a later point at low speeds of up to approximately 70 km/h or 50 mph. And as in the past, the driver still has the option to switch off PSM, meaning that it will only be active when he applies the brakes. The difference is that now the system is only reactivated by forcefully pushing down the brake pedal and thus exceeding the ABS control threshold on at least one front wheel. This gives the sporting driver greater freedom in his style of motoring, since PSM no longer intervenes when applying the brakes only slightly, thus allowing him to brake even more smoothly and with a neutral effect in bends.
    The operation and intervention of Porsche Stability Management also changes in response to the sports button, providing greater agility and driving dynamics. Accelerating out of a bend, for example, the car is even faster and more dynamic thanks to the higher anti-spin control threshold allowing more slip on the drive wheels when giving gas. The system thus consciously accepts greater swerve action at the rear - particularly on slippery surfaces - without endangering driving safety. The other PSM activation thresholds are likewise raised to a higher level allowing a bigger deviation between the actual and the desired movement of the vehicle before PSM cuts in. The result, clearly, is greater agility when driving to the limit in lateral dynamics. Raising the ABS intervention limits, in turn, the system allows the driver to apply the brakes with more neutral behaviour when entering a bend. A further point is that PSM allows more drag momentum from the engine whenever the driver takes his foot off the gas pedal, ensuring a smoother load change for taking bends with a tighter angle and in more dynamic style. And for even greater agility, all the driver has to do is switch off PSM with the sports mode active.
    -
    -

    Re: PSM advice

    Thanks gian61,

    That is certainly it, i have done as Carols suggested when we had a little snow this week and the PSM activated on acceleration, I was just not in enough trouble for it to activate!!

    Re: PSM advice

    P.S: With Sport Chrono switched on "sport",
    PSM is reactivated by forcefully pushing down the brake pedal and thus exceeding the ABS control threshold on both front wheel!
    -

    Re: PSM advice

    I find PSM very quick to react and quite violent in its action. I sorted that out last night by turing it off and now I can slide around roundabouts to me hearts content.

    Re: PSM advice

    FWIW my PSM (in my measely Boxster S) works perfectly and instantaneously.
    Just went for a cruis today with frost and very slick streets, and it reacted immediately when applying too much throttle in a corner.
    I have no idea how it will assist you if you enter a corner too fast, let go of the throttle and start oversteering..? It cant apply accelleration to the wheels..can it? Does it simply brake the appropriate front wheel?
    Argh!

    Re: PSM advice

    PSM didn't apply some accelleration to wheels by E-gas,
    somewhere in case of oversteering it apply brake force to internal front wheel,
    during understeering it apply brake to esternal rear wheel.
    -

     
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