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On track with or without PSM - Porsche Stability Managemnt

Do you turn off PSM on track?

  • I never turn PSM off on track

    Votes: 0 0.0%
  • Yes, I always turn PSM off

    Votes: 0 0.0%
  • I sometimes do turn PSM off but more On than Off

    Votes: 0 0.0%

  • Total voters
    0

Pip1968

Well-known member
Joined
26 Oct 2009
Messages
1,490
I was just pondering what most people as track goers generally do. I was at the Nordschleife over the weekend and was very lucky generally with the weather. Whilst I was there though another GT3 Mk I (Guards Red and German plated I believe) bit the dust with what I think was front end and side damage. It happended just after the sharp right at Kallenhard on the approach to "Miss-Hit-Miss" Wehrseifen.

Clearly a 996 being a non PSM GT3 some would say it is already at a disadvantage. Obviously PSM will not save you from every eventuality but......

So whilst I personally have no choice with a 996 GT3 who amongst the 997 and 991 track day enthusiasts turn PSM off? I am interested to hear those that rarely do and those that sometimes do as I am sure very few are black and white.

To keep some continuity I also turn off the DSC (BMW equivalent of PSM) on my BMW e46 M3 CSL when I go to the Nurburgring.

Pip
 
The 997.1 doesn't have PSM just a very basic traction control, which is about as much use as a chocolate tea pot. I alway run with it off.
 
I've grown up on the 996 platform. I turn everything off on the 997.2 as I do not rely on the aids and aim to drive to the mechanical grip of the car.

I also turn everything off as I do not enjoy the feeling of a second driver in the car as well as to reduce the load on the rear brakes. They can overheat and wear out quicker with all the added work taking place. Rear calipers can also discolour from additional heat.
 
All 996 GT, no systems.

997.1 has TC - Traction Control
997.2 has SC and TC - The Stability Control is different to the Stability Management (PSM) on the non GT Cars

The 997.2 has a modified PSM stability management system designed for the GT3, but has the option to deactivate the elements of both Stability Control (SC) and Traction Control (TC) in separate steps.

This gives the driver maximum control and crucially these functions are not reactivated automatically even under the most extreme driving conditions, but only at the touch of a said button. So no Porsche Management of the Stability Control, which is why it's just SC and TC and no PSM button, since PSM is designed to automatically reactivate.

Stability control (SC): will brakes individual wheels (front and/or rear) and/or cut engine power to correct for understeer or oversteer when cornering.

Traction control (TC): will brake individual drive (rear) wheels and/or cut engine power to prevent unnecessary wheel spin when accelerating.

For the 991 models, the systems moved up to Electronic Stability Control (ESC) and Traction Control (TC) and again no PSM Button, since PSM is designed to automatically reactivate.


FYI on PSM -Porsche Stability Management on non GT Cars

PSM is an automatic control system for providing stability at the limits of dynamic driving performance, and is a standard feature of every 911. Sensors work continuously to monitor the driving direction, speed, yaw velocity and lateral acceleration of the car. Using this information, PSM computes the actual direction of motion. If this direction deviates from the desired course, PSM initiates braking interventions targeted at individual wheels – recognisable by the flashing indicator light in the dash – in order to stabilise the vehicle.

Under acceleration on wet or low-grip road surfaces, PSM improves traction using the ABD (automatic brake differential) and ASR (anti-slip regulation) functions. The control interventions are smooth and precise, giving an agile response. When 'Sport' mode is selected on the optional Sport Chrono Package Plus, the PSM intervention threshold is raised to enable greater driver involvement – particularly at speeds of up to approximately 70 km/h / 45 mph.

The integrated ABS shortens the braking distance even further and the braking inputs are smooth and precise, thereby enhancing comfort.
An enhanced PSM system, now also available in rear-drive models, is characterised by two additional functions: the precharging of the brake system, and brake assist.

If the driver suddenly releases the accelerator pedal, the PSM automatically readies the braking system. With the braking system having been precharged, the brake pads are already in light contact with the brake discs. Maximum braking power is therefore achieved much sooner.

When sudden braking is detected – i.e. if the pressure on the brake pedal exceeds a predefined level – the brake assist function uses the PSM hydraulics to apply maximum brake pressure to all four wheels.

If you want a purely active driving experience, you always have the option to deactivate PSM. It is automatically reactivated, for your safety, only if either of the front wheels (in sport mode, both of the front wheels) requires ABS assistance. The ABD function, however, remains active at all times.

In conclusion, PSM offers a high level of driving stability and safety – and typical Porsche agility at the same time.
 
^thanks for that. Really helpful.

FWIW, on Sunday at the track, I left the PSM activated, as the track was wet. The car was very stable under braking, and the system only engaged on one section (a lowish speed slippery bit) to restrain me as I crossed the old dry (rubbered) line in the transition from one corner to the next, so I didn't feel that it was too intrusive.

In fact, I was grateful as I am no 'driving god', I'm not running a GT, and I was probably pushing too hard for the conditions. I do check brake disc/caliper temps on my return to the pits (a laser thermometer is wonderful for tyre and brake temps) and my rears were not overheating (which I assume would happen if you lean on the systems for the whole session).
 
A little long, and not mine, but makes interesting reading, particular the Thomas Herold comments at the end.


PSM monitors the 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. This enables the PSM to detect oversteer and
understeer. It basically determines the slip angle of the front and rear
tires, or more simply, when the car is not going where the steering wheel
is pointed. Oversteer is minimized by automatically applying the brake on
the outer front wheel in a bend, slowing the rotation of the car;
understeer is minimized by applying the brake on the inner rear wheel,
speeding the car’s rotation. No driver will be able to do that until
Porsche develops a car with four brake pedals. However, PSM is not only a
braking system. If you lift off the throttle in a low traction situation
(wet, snow, etc.) and the back of the car gets loose, PSM will increase
the engine speed (blip the throttle) to keep the car in line. Also, if
traction is low, PSM can use engine braking (EDC â€' engine drag torque
control) to slow the car. PSM can calculate the amount of available
traction by comparing wheel speeds at all four corners of the car.

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.

However, if you require more fun, you can turn the PSM off. When you
"turn it off," you are taking only the outputs offline. The PSM system is
still collecting data from the ABS system, the yaw sensor, the lateral
acceleration sensors and the steering wheel position sensor. If you have
PSM off, and the levels of slip are exceeded, and you do not touch the
brakes, the car will continue to slide. If you have not exceeded the
levels of slip allowed, and apply the brakes (no matter how hard), PSM
will not active its outputs. However, if you have exceeded the levels,
AND apply the brakes (no matter how hard), PSM will activate until the
car has regained control or you get off the brakes, at which point PSM
stops outputting. PSM assumes that since you hit the brakes that you are
not comfortable with the level of sliding and that you want it to help.
This answers the question, posed by Mike Furnish on the PCASD forum, that
inspired this article, "what happens in a spin when you put both feet
in?" Presuming that you put in the correct two pedals, PSM will activate.

So what about PSM and racing? At this point in my career, PSM is an asset
to my racing. It has allowed me to more confidently explore the limits of
traction on the first few laps at a new track, particularly in scarier
corners, e.g., Turn 8 at Willow Springs. I was very happy to have it at
Phoenix International Raceway, a track with concrete barriers everywhere.
When PSM activates you can feel it, much like you can feel ABS. It will
show you where you are losing traction while keeping you on the track if
the loss was unintentional. When it engages, it may slow you down where
you might not want it to later, i.e., where you really do want more
oversteer, but on those first few practice laps, who cares? You can
actually throttle steer the car quite well with PSM on as long as you are
smooth, the yaw is not excessive, and the corner is fast enough to allow
smooth inputs. This in itself is a good training tool. So PSM is good for
practice, but what about when it matters, during timed laps?

In a time trial situation, it would depend on the course whether it would
matter if PSM were on or off. On a tight road course, you would most
likely want it off. On an autocross track, you want it off for sure. If
you had sufficient presence of mind on a road course you could turn it on
and off depending on the corner. You could make sure it’s off for Turn 2
and 4 at Willow Springs, turns where throttle steering comes into play.
You could turn it on for Turn 8, the last place on earth you want to see
your tail catching up with you. I've never done this, but it illustrates
the point.

So far, so good. Since you can turn PSM off, why wouldn’t you want to buy
it, even for a car you intend to race? It seems like the best of both
worlds. However, remember above where I said that when PSM is off, it is
still collecting data and if you hit the brakes when the levels of slip
are exceeded, it will intervene. That could be a negative in one racing
technique, trail braking, where you are obviously on the brakes and
turning. There are two reasons to trail brake, one in which PSM is
neutral or even a positive, and one in which it can interfere with the
driver’s intention. The first is when you are trail braking to lengthen
the straight or to maintain a higher speed through the first part of a
turn. In this case, you want the car to stay on its directed path. If
things are going as intended, PSM is very unlikely to engage even though
you are on the brakes. If it does, it is probably because you lost rear
traction in a pretty big way. By engaging it didn’t cost you time since
your intention was to slow down anyway and it may have saved you from
spinning. The second use of trail braking serves a different purpose. If
you are trail braking to induce some oversteer intentionally to tighten
the corner, PSM could interfere in the same way as when it is on and you
lift to oversteer. While I have a lot of experience throttle steering the
car, with PSM on and off, I don’t brake to loosen the rear of my 996 C2.
Lifting is normally sufficient. However, I have seen this technique, in
the form of left-foot braking, used in a friend’s 993 C4 in Turn 4 at
Willow and Turn 5b at Spring Mountain and presume it would be useful in
the newer 996 C4. Since the 993 does not have PSM, I cannot tell you to
what extent it would have interfered. If you are smooth, probably very
little, if at all. But, this is one possible negative to weigh against
the aforementioned positives. I think it’s worth it, but let me give the
last word to Porsche.

"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."

"The difference is small around the Nurburgring for a skilled test
driver," he explained. "Within one second a lap in fact. This is the way
the car is made. 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, so an aggressive driver will be slower with the
system on."
 
crash7 said:
A little long, and not mine, but makes interesting reading, particular the Thomas Herold comments at the end.


PSM monitors the 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......etc etc"

Interesting read that and does de mystify it well. I turn TC and PSM off on a circuit as I don't care for the 'second driver" having a go either :). They never seem to do what you expect them to! Im no driving god but do want to feel what the car is up to from my inputs not the cars. Road driving is generally far less predictable so leave it on mostly apart from smokey burn outs leaving waitrose car park.
 
An interesting read. So it appears that PSM is never really off even if switched off as it will engage if you brake and the car is anyway unstable.

I should have added another dimension to the poll to see if those track day attendees that have opted for the 'automatic' version of the GT3 are also more likely to keep all the aids switched 'On'. They are presumably less bothered about driver involvement and instead seek the easist solution to a quick lap time. :?:

Pip
 
Pip1968 said:
An interesting read. So it appears that PSM is never really off even if switched off as it will engage if you brake and the car is anyway unstable.

I should have added another dimension to the poll to see if those track day attendees that have opted for the 'automatic' version of the GT3 are also more likely to keep all the aids switched 'On'. They are presumably less bothered about driver involvement and instead seek the easist solution to a quick lap time. :?:

Pip

The article quoted's reference is the 996 C4, so quite an ancient analysis and i doubt the systems are the same today. It says PSM will engage if you are outside its defined limits AND stand on the brakes. A fair assumption that you're not intending the car to do such so a an option worth having id think.

I really dont think it lessens driver involvement unless beeing backwards in the armco makes you feel more invloved :floor:

Its an optional driver aid, same as decent tyre or decent suspension or brakes.
 
Pip1968 said:
An interesting read. So it appears that PSM is never really off even if switched off as it will engage if you brake and the car is anyway unstable.

I should have added another dimension to the poll to see if those track day attendees that have opted for the 'automatic' version of the GT3 are also more likely to keep all the aids switched 'On'. They are presumably less bothered about driver involvement and instead seek the easist solution to a quick lap time. :?:

Pip

Pip, as I wrote in my response, the 997.2 GT3 onwards has SC and TC which can be controlled by the driver and remain off, which is why PSM is not found on the GT3 or RS. Its Stability Control without the Management.
 
997.2 GT3 - everything off. I hit the anchors fairly hard and trail brake a lot on track and if you do that in the dry with PSM on then the system feels like it is resisting weight transfer on turn in and also obliterates your rear brakes.

(Background : when I first got the 997 I ran with it on for a couple of trips {confidence issue at the time having destroyed its 996 GT3 predecessor in a crash that PSM would likely have caught} and I managed to warp rear disks {the internet has people who deny that this is even possible} and consume rear pads at the same rate as front {which again should not happen on a GT3}. Turning it off resolves all of the issues and makes you able to balance it more like a 996, which is what I prefer).
 
Senoj said:
I really dont think it lessens driver involvement unless beeing backwards in the armco makes you feel more invloved :floor:

Its an optional driver aid, same as decent tyre or decent suspension or brakes.

We will agree to disagree here Senoj. Tyres and suspension are passive 'intervention' (Aside from the active dampers PASM which will again lesson the involvement) whilst TC is an active intervention. It affects your input to correct the situation when it deems things are going 'wrong'. If not why have the ability to turn it off on GTs???

Why drive at all on track if you dont want the risk of ending up in the armco. Why do people drive with Cup tyres and risk aquaplaning or ending up in the armco (weather is never a certainty). Why drive the Nordschleife when on most of the track there is little run off - if you are risk averse then stick to disused flat runways in the dry.

The whole point for many is driver involvement. Man and machine verses track. No aids, good tyres and geometry/suspension set up. The easy option is all weather tyres in an 'auto' GT3 RS with all systems 'ON' but I dont think you can say that this is the most involving/interactive solution on the basis that you may not end up in the armco.

I would argue that the more aids the less the driver skill. Already you see the younger generation who think they are driving gods just because they are able to lap a track quickly in a safety enhanced car (TC/PASM, rear parking camera/sensors, auto wipers, automatic headlights, crossing a white line warning system et cetera et cetera). Take away those items are they are out of their comfort zone. They have become lazy and cosseted by these aids.

Don't get me wrong Senoj each to their own and you are probably 'lucky' in that you have experisnced the pre 'safety' car era although prefer aids to involvment and what you perceive as increased risk.

I think the 996 GT3/RS are the last of the fully interactive and most driver involving Porsche.

Pip
Ps I did text you (obviously and old number) and send a PM to be able to get you that drink. I also popped into the Dorint bar on Sunday but did not see you. I hope that you had a 'safe' couple of days on track.
 
I recently had a conversation about driver aids with two pro drivers, both of which instruct.

They commented on how amateur track day drivers love the 'hero button' and think it makes them better drivers and more involved when they switch everything off, aka being a hero.

Their take was that if your smooth driver aids do not intervene both also commented that F1 cars and most GT race cars now a days all utilise driver aids.

Each to their own!
 
I found that it's the yaw sensors that do you on the track. Just after the apex they try and tie you in knots!!
The Cat driving course made me decide how capable My car is when it works with me
 
crash7 said:
I recently had a conversation about driver aids with two pro drivers, both of which instruct.

They commented on how amateur track day drivers love the 'hero button' and think it makes them better drivers and more involved when they switch everything off, aka being a hero.

Their take was that if your smooth driver aids do not intervene both also commented that F1 cars and most GT race cars now a days all utilise driver aids.

Each to their own!

That is a generic comment which makes sense but I think less specific to some of the people here.

I rather not burn through rear brakes at a high rate, discolour rear calipers, etc. There are no prizes for a lap time and therefore it is all about personal experience. As someone commented above, the 996 has the purest experience before the later cars introduced interventions. Those of us who have been fortunate to experience the joys of a 996 are aiming to extract an evolution of that experience in the newer cars.

Many coaches tend not to run a personal GT3 for multiple years and probably move on from the car before bits need replacing (or someone else foots the bill).

For all out laptime, yes a PDK with full aids is probably quicker and in time one can drive in 'sync' with the aids.
 

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