Switching off PSM?
Discussion
Okay maybe I am sad and have nothing better to think about, but does anyone know what actually switches off when you choose to disengage PSM? Call me old fashioned but I like to know what is happening when I push a button.
I have a 2003 996TT but I guess the same basic system applies for all 996/997 PSM systems.
The flowery language from the brochures says abilty to control fuel, throttle, apply braking to wheels individually, as well as channelling power to wheels with grip.
What I am not sure of is if PSM is turned off are some of these components unaffected e.g;
a) any impact on the ABS system ? I understand it is still engaged but does the driver get more control with PSM off ?
b) what impact on power distrubtion through the four wheel drive system? Is ayone familiar with what impact PSM has (if any) on power distrubtion ? What are the differences when PSM is on v. off ?
Or indeed if anyone knows of other changes in the way the car will drive ........ perhaps not noticeable on the road, but on track ?
I have a 2003 996TT but I guess the same basic system applies for all 996/997 PSM systems.
The flowery language from the brochures says abilty to control fuel, throttle, apply braking to wheels individually, as well as channelling power to wheels with grip.
What I am not sure of is if PSM is turned off are some of these components unaffected e.g;
a) any impact on the ABS system ? I understand it is still engaged but does the driver get more control with PSM off ?
b) what impact on power distrubtion through the four wheel drive system? Is ayone familiar with what impact PSM has (if any) on power distrubtion ? What are the differences when PSM is on v. off ?
Or indeed if anyone knows of other changes in the way the car will drive ........ perhaps not noticeable on the road, but on track ?
IIRC there are differences in what PSM can do with 4WD and without. On the Turbo I believe it can vary power delivery from 90% rear, 10% front to 60% rear, 40% front - Daz will confirm or deny I'm sure.
2WD PSM obviously can't do that...but it CAN brake wheels individually.
If you switch PSM off then ABS is still active but traction is controlled solely by your right foot and the car will be allowed to both understeer and oversteer based on corner entry speed and right foor on the exit.
Personally I am happy to leave PSM switch ON on a Track Day as it doesn't actually cut in unless the car is already sliding significantly...basically the light only goes on when you've stuffed it up - rather than cutting in and preventing any fun like on some cars...
Obviously if you want slide the car about on a drift day you're going to have to switch it off.
Great system. Not foolproof. But great. And it has never yet got in the way of any of my evil plans on track. When I finally go drifting for a laugh with Captain Sideways I'll remember to disable it.
2WD PSM obviously can't do that...but it CAN brake wheels individually.
If you switch PSM off then ABS is still active but traction is controlled solely by your right foot and the car will be allowed to both understeer and oversteer based on corner entry speed and right foor on the exit.
Personally I am happy to leave PSM switch ON on a Track Day as it doesn't actually cut in unless the car is already sliding significantly...basically the light only goes on when you've stuffed it up - rather than cutting in and preventing any fun like on some cars...
Obviously if you want slide the car about on a drift day you're going to have to switch it off.
Great system. Not foolproof. But great. And it has never yet got in the way of any of my evil plans on track. When I finally go drifting for a laugh with Captain Sideways I'll remember to disable it.
As far as I know, turning PSM off does not affect the 4WD transfer of power, as that is a mechanical rather than electronic system.
PSM off prevents the car from controlling throttle and brake, although as you say it still allows ABS to function
Oh, and turning PSM off is noticeable but mainly as Don says when you've overcooked it...
>> Edited by willr on Monday 1st August 12:06
PSM off prevents the car from controlling throttle and brake, although as you say it still allows ABS to function
Oh, and turning PSM off is noticeable but mainly as Don says when you've overcooked it...
>> Edited by willr on Monday 1st August 12:06
In a 997S the PSM button turns the car from 'fun' into 'ultra fun'
With it engaged the car is a little boring particularly on track where it is far too nannying. Turn it off and the car becomes awesome allowing you to stick down as much power as you like. Unfortunately turning PSM off is also like turning your wallet upside down while open as your tyres dissapear like ice in a boiling kettle.
With it engaged the car is a little boring particularly on track where it is far too nannying. Turn it off and the car becomes awesome allowing you to stick down as much power as you like. Unfortunately turning PSM off is also like turning your wallet upside down while open as your tyres dissapear like ice in a boiling kettle.
When you switch PSM off it is re-activated under braking (and then deactivated when foot is lifted off the brake again).
Sorry I disagree with Steve Rance, in the wet a car with PSM is significantly safer than one without, and having the option to turn off for track is excellent. If I could have it in my GT3 I would in an instant, it would significantly extend the driveability in the winter, and stop me worrying about downpours as much while wearing R-compound boots.
Sorry I disagree with Steve Rance, in the wet a car with PSM is significantly safer than one without, and having the option to turn off for track is excellent. If I could have it in my GT3 I would in an instant, it would significantly extend the driveability in the winter, and stop me worrying about downpours as much while wearing R-compound boots.
I have only used the car once on track, and my (brief) experience was that PSM only kicked in as Don says, when you have pushed it that little bit too far, rather than it being intrusive.
I have just checked the sales material that Porsche put out, and it says ''it (PSM) is also particularly valuable under acceleration when the REAR wheels do not have equal grip, where it improves traction and keeps the car on line''
Questions arise, 1. does that mean it acts like traction control ? 2. there is no specific mention of traction control but surely applying a brake to a spinning wheel cannot be good ? 3. What about the front wheels, does it not apply to them ?
Is the system essentially the same as electronic stability control but Porsche are trying to wrap it up in fancy language to make it sound more than it is, or is there something more involved?
It seems to work though, and the fact it can be kept switched on for track without completely destroying all the fun appears to be a good thing... I think !
>> Edited by mogv8 on Monday 1st August 14:34
>> Edited by mogv8 on Monday 1st August 14:37
I have just checked the sales material that Porsche put out, and it says ''it (PSM) is also particularly valuable under acceleration when the REAR wheels do not have equal grip, where it improves traction and keeps the car on line''
Questions arise, 1. does that mean it acts like traction control ? 2. there is no specific mention of traction control but surely applying a brake to a spinning wheel cannot be good ? 3. What about the front wheels, does it not apply to them ?
Is the system essentially the same as electronic stability control but Porsche are trying to wrap it up in fancy language to make it sound more than it is, or is there something more involved?
It seems to work though, and the fact it can be kept switched on for track without completely destroying all the fun appears to be a good thing... I think !
>> Edited by mogv8 on Monday 1st August 14:34
>> Edited by mogv8 on Monday 1st August 14:37
A well driven car without it will be quicker than with it fitted. Modern chasis are relatively forgiving even with the generally high power outputs of most sports cars. The 911 is not that difficult to drive in the wet. In the GT battle it was one of the fastest cars in difficult conditions on scrubbed Pilot cups. This was against cars wwith much higher outputs and every driver aid known to man. I wouldn't say it was that easy putting the times in but any reasonable driver could have kept it on the island.. If porsche can come up with a system that overcomes aquaplaning.... Well that's a different story
))
)) mogv8 said:
I have only used the car once on track, and my (brief) experience was that PSM only kicked in as Don says, when you have pushed it that little bit too far, rather than it being intrusive.
How do you know you pushed it a little too far if you didn't turn it off?
I have done several wet trackdays in mine and the car is a lot slower with PSM on than with it off. PSM is constantly being far too conservative in the wet. Turn it off and try again and you will find the car will take the same bend a lot faster and feel much more fun while doing so. Admittedly with it on you don't have to worry about full on 3rd gear broadsides but hey that is just part of the fun
Interesting views:
My experience is that PSM is not overly conservative in the wet. Whilst being somewhat tongue in cheek about being good in the wet I have overtaken a good few more powerful cars with it chucking it down in my Boxster S - PSM equipped. Not that the PSM light was going much - more that I think it gives one a psychological boost knowing that it will step in and help if you stuff it up...so you try harder.
I can vouch for the system, as can derestrictor, where it kept us on the black stuff on the exit of Copse...
As to it "coming on under braking" - well this is its ABS functionality as I understand it and you cannot turn this off.
Whilst 4WD is a mechanical system I understood that PSM could "interfere" with it? Happy to be corrected by an owner of a 4WD PSM equipped vehicle...
The purists will always argue that a car without electronic aids is better. I drive a TVR (no ABS, no "PSM", no nothing and 260bhp per tonne) and IMHO whilst not having the aids is OK, I'm old enough to take responsibility for my actions, but PSM is a good enough system NOT to pee me off whilst definitely being of assistance...
My experience is that PSM is not overly conservative in the wet. Whilst being somewhat tongue in cheek about being good in the wet I have overtaken a good few more powerful cars with it chucking it down in my Boxster S - PSM equipped. Not that the PSM light was going much - more that I think it gives one a psychological boost knowing that it will step in and help if you stuff it up...so you try harder.
I can vouch for the system, as can derestrictor, where it kept us on the black stuff on the exit of Copse...
As to it "coming on under braking" - well this is its ABS functionality as I understand it and you cannot turn this off.
Whilst 4WD is a mechanical system I understood that PSM could "interfere" with it? Happy to be corrected by an owner of a 4WD PSM equipped vehicle...
The purists will always argue that a car without electronic aids is better. I drive a TVR (no ABS, no "PSM", no nothing and 260bhp per tonne) and IMHO whilst not having the aids is OK, I'm old enough to take responsibility for my actions, but PSM is a good enough system NOT to pee me off whilst definitely being of assistance...
jjr1 said:
[quote=mogv8]I have only used the car once on track, and my (brief) experience was that PSM only kicked in as Don says, when you have pushed it that little bit too far, rather than it being intrusive.
''How do you know you pushed it a little too far if you didn't turn it off?''
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The answer is the car tells you when it kicks in, (a light on the dash) and it only happened once which was tail out in the wet. In terms of being quick the tail was certainly too far out to be good, well before the PSM light flickered.
On this basis I don't think it impacted on lap times negatively (in case you wondering -yes I have driven on track enough times in other cars with no more than a slip diff, so I usually know how to find the limit). I only left PSM on as the track was so narrow. Hopefully next time there will be more space.
The one thing that did intrude where I thought I could have improved lap times was ABS, which seemed to kick in earlier than I thought it should, but the surface was a little bumpy, so I put it down to that.
>> Edited by mogv8 on Monday 1st August 15:50
I can't argue about the abs being a pain as it gets very easily confused by bumps on a track which can be a little scary if you leave braking very late.
We will just have to agree to disagree about PSM though as there are clearly two camps very much divided on whether it is intrusive or not. I personally couldn't care less if I had it in the car or not as I just turn it off as soon as I want to go fast.
We will just have to agree to disagree about PSM though as there are clearly two camps very much divided on whether it is intrusive or not. I personally couldn't care less if I had it in the car or not as I just turn it off as soon as I want to go fast.
On a different note, some stability/tractions systems also work by applying the brakes on individual wheels. On track, I'd have thought that could lead to overheated brakes on an already hard worked set of brakes.
Does Porsche's PSM system work in this way or just reduce the throttle?
Does Porsche's PSM system work in this way or just reduce the throttle?
I had the dubious honour of demmoing the Mitsi Evo 5 to the press at Donnington. Very trick, loads of power and an utter waste of time on the circuit. Didn't need a driver only someone to point it. You could feel the diffs and traction systems working. All very clever but the car refused to let me put the power down when I wanted to.. Apparently it knew better. On a lap it was no quicker than the MK1 Elise that I drove there a week earler. Except the elise didn't root it's tyres, loose 2nd 3rd and 4th gears, its brakes and spew it's coolant all over the pits..
)
) Well, if it works on the brakes, then I would have thought having PSM engaged on a dry track is a bad thing, leaving aside any other arguements on handling. On a wet track, overheating brakes wouldn't be such an issue so leaving PSM engaged would be OK (and maybe useful) if that was your preference.
On a 2wd 996 the psm will brake individual wheels. I overcooked it at Goodwood , was going slightly too fast and was drifitng wide. As soon as I had realised it I had overcooked it, you could feel the individual wheels brake and tug you back on line.
(it wont over heat the brakes if your not relying on it all the time - hence I would leave it on. Its not very intrusive)
It save me for a gentle off into the gravel. No doubt.
On my first 996tt, I too thought that you could pust it and push it and wow what a super car, best 4x4 psm and all that. When I really over cooked it, there is nothing that will save you. hence a close encounter with 2 trees.
If you havnt got grip, neither has the psm. It will only save an error upto a limited point. So on the road drive carefully and dont rely on the psm to save you, drrive with the aim of not seeing the psm light.
>> Edited by superlightr on Monday 1st August 16:35
(it wont over heat the brakes if your not relying on it all the time - hence I would leave it on. Its not very intrusive)
It save me for a gentle off into the gravel. No doubt.
On my first 996tt, I too thought that you could pust it and push it and wow what a super car, best 4x4 psm and all that. When I really over cooked it, there is nothing that will save you. hence a close encounter with 2 trees.
If you havnt got grip, neither has the psm. It will only save an error upto a limited point. So on the road drive carefully and dont rely on the psm to save you, drrive with the aim of not seeing the psm light.
>> Edited by superlightr on Monday 1st August 16:35
Every Porsche owner needs to learn how to apply the throttle hard to get themselves out of a rear end slide induced by breaking late into the corner,
I thought thats why we bought them
PSM off....unless your feeling bit off weather, its raining, there is a risk of aqua-planing down the main straight (happened at Cadwell), tyres have had it, or the car is having a bad handling day.
I thought thats why we bought them
PSM off....unless your feeling bit off weather, its raining, there is a risk of aqua-planing down the main straight (happened at Cadwell), tyres have had it, or the car is having a bad handling day.
PSM only works by braking and varying power to the wheels, so if you are not applying power then it can't vary this, also it can't apply power for you.
On a 4wd car the power can vary (on a 996/997) from 5% to 40% (front), so this combined with PSM can work very well.....provided you are applying throttle.
With a Tiptronic/4wd system, PSM will engine brake deploying load to each corner if necessary.
Damian
On a 4wd car the power can vary (on a 996/997) from 5% to 40% (front), so this combined with PSM can work very well.....provided you are applying throttle.
With a Tiptronic/4wd system, PSM will engine brake deploying load to each corner if necessary.
Damian
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