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Jun 2, 2008 8:03:58 PM
- rantanplan
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Jun 2, 2008 8:19:12 PM
- Trundle_GT3
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Re: Question about PSM and understeer
Quote:
ResB said:
Does switching PSM off on the 997 assist with understeer particularly on the track?
In a word NO
If you are experiencing alot of understeer most likely you are overdriving the car. If the car is not turning the reaction that most do is to turn the wheel more...which is the wrong correction.
Leave PSM on, its parameters are quite wide.
Do yourself a favor and attend a high performance driving school (PSDS) to better learn vehicle dynamics and car control. Money well spent!
Jun 2, 2008 8:27:46 PM
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Carlos from Spain
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Re: Question about PSM and understeer
Like Antonio says, with PSM off you will decrease the understeer since it will allow for oversteer to occur, controlled or uncontrolled.
PSM tries to control the car when the car looses it "pose", but if its too much for the PSM to counter (laws of physics still apply) and the car is going to go, instead of letting whatever happen, it will try to induce understeer (the least bad of the scenarious) so that it is easier to recuperate control by simply lifting the throttle, otherwise you can spin through ovesteer, get snap-oversteer, etc. Thats why you get so much understeer with PSM, artificially induced understeer, i.e. in situation were you should be getting oversteer like too much throttle coming out of a bend, you still get understeer with PSM.
I have found though that with Sport Chrono ON, if you are progressive you can get a reasonable amount of oversteer without the PSM getting to the point of inducing understeer. SO that it doesn't get in the way much. Have you tried the sport button?
PSM tries to control the car when the car looses it "pose", but if its too much for the PSM to counter (laws of physics still apply) and the car is going to go, instead of letting whatever happen, it will try to induce understeer (the least bad of the scenarious) so that it is easier to recuperate control by simply lifting the throttle, otherwise you can spin through ovesteer, get snap-oversteer, etc. Thats why you get so much understeer with PSM, artificially induced understeer, i.e. in situation were you should be getting oversteer like too much throttle coming out of a bend, you still get understeer with PSM.
I have found though that with Sport Chrono ON, if you are progressive you can get a reasonable amount of oversteer without the PSM getting to the point of inducing understeer. SO that it doesn't get in the way much. Have you tried the sport button?
Jun 2, 2008 8:39:14 PM
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ResB
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Re: Question about PSM and understeer
Quote:
rantanplan said:
u will only be able to truely find out what ur carrera s is capable of when switching the PSM off. otherwise u wont be able to feel the car to the same extend..and yes, it will definately overstear, but thats the purpose;) right..?
To a degree yes. I have and do often turn PSM off when I'm feeling spontaneous and yes, there is a big difference. We would all like to be able to get the back end out and release huge drifts, but to be honest I'm not that concerned with this.
I'm going to have a mess around on the track over the next few weeks and experiment a little, focussing on the driving enjoyment as opposed to being the quickest I can.
I just wondered if turning PSM off it helped with understeer just like the CSL does apparently.
Quote:
Trundle_GT3 said:Quote:
ResB said:
Does switching PSM off on the 997 assist with understeer particularly on the track?
In a word NO
If you are experiencing alot of understeer most likely you are overdriving the car. If the car is not turning the reaction that most do is to turn the wheel more...which is the wrong correction.
Leave PSM on, its parameters are quite wide.
Do yourself a favor and attend a high performance driving school (PSDS) to better learn vehicle dynamics and car control. Money well spent!
I am experimenting with trail braking and weight transfer through the bends and I believe I'm getting better and also more confident with the cars characteristics. However, I really do need some tuition.
So couldn't agree with you more.
Jun 2, 2008 8:44:27 PM
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ResB
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Carlos from Spain
Re: Question about PSM and understeer
Quote:
Carlos from Spain said:
Like Antonio says, with PSM off you will decrease the understeer since it will allow for oversteer to occur, controlled or uncontrolled.
PSM tries to control the car when the car looses it "pose", but if its too much for the PSM to counter (laws of physics still apply) and the car is going to go, instead of letting whatever happen, it will try to induce understeer (the least bad of the scenarious) so that it is easier to recuperate control by simply lifting the throttle, otherwise you can spin through ovesteer, get snap-oversteer, etc. Thats why you get so much understeer with PSM.
I have found though that with Sport Chrono ON, if you are progressive you can get a reasonable amount of oversteer without the PSM getting to the point of inducing understeer. SO that it doesn't get in the way much. Have you tried the sport button?
I have and do like the more responsive actions of the car when the Sport button is depressed and PASM is on. Certainly exiting curves feels quicker on the track.
Jun 2, 2008 8:48:37 PM
- ADias
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Re: Question about PSM and understeer
Quote:
Trundle_GT3 said:Quote:
ResB said:
Does switching PSM off on the 997 assist with understeer particularly on the track?
In a word NO
If you are experiencing alot of understeer most likely you are overdriving the car....
Or... his alignment could be way off...
Jun 2, 2008 9:00:50 PM
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Carlos from Spain
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Re: Question about PSM and understeer
True that if you are getting severe understeer constantly it means that you are pushing the car too much causing PSM to kick in excesively and you should "go slower to go faster" or a grip problem like worn tires, alignment being way off, etc. But that is not what I think ResB is complaining about, I think he is complaining of the character of the car's handling being so much prone to understeer due to PSM 
The rpoble is that with PSM "on" ALL you get is understeer, you can't get oversteer so its normal to complain of it being prone to understeer with it ON even if the car is OK, and if its not, you still get understeer so that wouldn't change things.
With PSM off you would be getting both depending on the situation, but with it ON you get understeer, and more understeer.
The rpoble is that with PSM "on" ALL you get is understeer, you can't get oversteer so its normal to complain of it being prone to understeer with it ON even if the car is OK, and if its not, you still get understeer so that wouldn't change things.
With PSM off you would be getting both depending on the situation, but with it ON you get understeer, and more understeer.
Re: Question about PSM and understeer
Quote:
ADias said:Quote:
Trundle_GT3 said:Quote:
ResB said:
Does switching PSM off on the 997 assist with understeer particularly on the track?
In a word NO
If you are experiencing alot of understeer most likely you are overdriving the car....
Or... his alignment could be way off...
Alignment is fine.
Checked after the Mini issue at the Ring this year. I should say I'm managing my understeer, but I should be a lot quicker...
Jun 2, 2008 9:12:50 PM
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ResB
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Carlos from Spain
Re: Question about PSM and understeer
Quote:
Carlos from Spain said:
True that if you are getting severe understeer constantly it means that you are pushing the car too much causing PSM to kick in excesively and you should "go slower to go faster" or a grip problem like worn tires, alignment being way off, etc. But that is not what I think ResB is complaining about, I think he is complaining of the character of the car's handling being so much prone to understeer due to PSM
The rpoble is that with PSM "on" ALL you get is understeer, you can't get oversteer so its normal to complain of it being prone to understeer with it ON even if the car is OK, and if its not, you still get understeer so that wouldn't change things.
With PSM off you would be getting both depending on the situation, but with it ON you get understeer, and more understeer.
Absolutely. So, if disabling PSM induces the possibility of oversteer, then the answer must surely be yes, understeer will be less, but to what extent will only be found out on the track.
I'm seriously going to look at tuition and hopefully try to relay any results back to the forum. I think the findings will be quite interesting.
Jun 2, 2008 11:17:44 PM
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Carlos from Spain
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Re: Question about PSM and understeer
Quote:
ResB said: So, if disabling PSM induces the possibility of oversteer, then the answer must surely be yes, understeer will be less, but to what extent will only be found out on the track.
Spot on
I have done a few of those PSM vs no PSM courses were you drive through curves with ice, emergency braking with right tires on wet, instructor pulling the emergency brake on you at mid corner, etc and it really drives the point home on what PSM does, how the car ahndles with it on vs off, and how to react with it on vs off. Really usefull IMO.
Jun 3, 2008 3:10:59 AM
- U Boat Commander
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Jun 3, 2008 4:11:17 AM
- Silver Bullet
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Re: Question about PSM and understeer
"if disabling PSM induces the possibility of oversteer, then the answer must surely be yes, understeer will be less, but to what extent will only be found out on the track."
While there seems to be a logic in that, it really doesn't make sense and I don't think it is true.
Under and oversteer happen under different circumstances, so how PSM handles one dosen't really influence the other.
The 911 tends to understeer because it is much easier to have the front wheels slip than the rear, and that in turn is due to the fat rear wheels and most of all, the rear weight bias. Most people think that 911's oversteer, but the natural tendancy is actually understeer.
Understeer is made worse by over driving the car, as a previous post has suggested.
TO minimize understeer, remember the slow in and fast out rule (using trail braking as part of the slow in), and secondly, treat the gas pedal like a dial rather than an on/off switch. Finally, smooth weight transfers rather than jerky ones help to eliminate understeer.
When you do feel understeer, come off of the gas, slow down, and let the car turn.
PSM doesn't cause understeer; believe it or not, it actually helps correct it by doing what I outlined above.
While there seems to be a logic in that, it really doesn't make sense and I don't think it is true.
Under and oversteer happen under different circumstances, so how PSM handles one dosen't really influence the other.
The 911 tends to understeer because it is much easier to have the front wheels slip than the rear, and that in turn is due to the fat rear wheels and most of all, the rear weight bias. Most people think that 911's oversteer, but the natural tendancy is actually understeer.
Understeer is made worse by over driving the car, as a previous post has suggested.
TO minimize understeer, remember the slow in and fast out rule (using trail braking as part of the slow in), and secondly, treat the gas pedal like a dial rather than an on/off switch. Finally, smooth weight transfers rather than jerky ones help to eliminate understeer.
When you do feel understeer, come off of the gas, slow down, and let the car turn.
PSM doesn't cause understeer; believe it or not, it actually helps correct it by doing what I outlined above.
Jun 3, 2008 5:03:49 AM
- ADias
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Re: Question about PSM and understeer
Quote:
Silver Bullet said:...
TO minimize understeer, remember the slow in and fast out rule (using trail braking as part of the slow in), and secondly, treat the gas pedal like a dial rather than an on/off switch. Finally, smooth weight transfers rather than jerky ones help to eliminate understeer.
When you do feel understeer, come off of the gas, slow down, and let the car turn.
PSM doesn't cause understeer; believe it or not, it actually helps correct it by doing what I outlined above.
Excellent explanation on driving dynamics. It applies to other cars too, like my Vette. Most drivers these days drive digitally - brake full on or off, throttle full on or off. The art is smoothness and analog controls.
Re: Question about PSM and understeer
Porsche are organising courses that are called ' driving and mastering you car with no electronic assistance ' ( translated from french ) . I will be attending one of then at the end of the month at the Paul Ricard ( Le Castellet) track.
On my car with sports chrono on I can induce oversteer to quite some extend.
I do find that understeer does not come in before the PSM kicks in. And if PSM kicks in it means I have been too fast comming into the corner. ( this with sports chrono ON, with sports chrono OFF the car is not drivable fast on the track, as it kicks in way too early and then their is loads of understeer, not even mentioning the ABS kicking in so early that one can not make a proper late braking )
One often wants to come into the corner too fast.....
On my car with sports chrono on I can induce oversteer to quite some extend.
I do find that understeer does not come in before the PSM kicks in. And if PSM kicks in it means I have been too fast comming into the corner. ( this with sports chrono ON, with sports chrono OFF the car is not drivable fast on the track, as it kicks in way too early and then their is loads of understeer, not even mentioning the ABS kicking in so early that one can not make a proper late braking )
One often wants to come into the corner too fast.....
Jun 3, 2008 7:43:26 AM
- rantanplan
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Gnil
Jun 3, 2008 10:00:17 AM
- Ferdie
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Re: Question about PSM and understeer
Quote:
Silver Bullet said:
Finally, smooth weight transfers rather than jerky ones help to eliminate understeer.
Not only that, it minimizes load-change reactions on such a rear-engined vehicle as well. Other than that, great write-up.
Res, the PSM system minimizes both under- and oversteer on a car by selective brake applications. However it is more effective in the later. Have you driven a Boxster fast? I suppose you would not experience the same habit, as its weight distribution is more adequate. The understeer you mentioned is due to the 911's layout and, as said above, requires an appropriate driving style.
Jun 3, 2008 11:55:01 AM
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Carlos from Spain
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Re: Question about PSM and understeer
Quote:
Silver Bullet said:Under and oversteer happen under different circumstances, so how PSM handles one dosen't really influence the other.
PSM doesn't cause understeer; believe it or not, it actually helps correct it by doing what I outlined above.
It does because when the car tends to understeer (coming in too fast into a corner for example) the PSM will correct it but if its overwhealming it will understeer regardless of PSM. However, if the car is in another situation were oversteer is induced (too much throttle or too early on the exit of a corner or trailbraking into a corner for example), PSM again will correct it but if its if its overwhealming, you will not oversteer however, PSM will induce understeer so that if it goes, at least it doesn't go in oversteer since that would be much more dangerous because you spin.
So while PSM helps correct under and oversteer, if it can't it will only allow one to occur for safety reasons.
For example, there is ice or mud in a corner at the track and you floor violently the throttle at mid corner. Without PSM in a RWD car you will instantly go into oversteer and likely spin. Yet if you try this with PSM "on" you will not oversteer, you will always run wide with understeer no matter what, time and time again. You won't spin, you simply let off the throttle, open up the steering angle a bit and regain control. Thats the PSM inducing understeer rather than allowing you to spin. Thats why with PSM all you notince when you loose traction is understeer. Unless you activatre the sport button in sport chrono cars, in that case there is a significant amount of oversteer allowed and PSM is much harder to kick in, usually not at all even at the track unless you make a mistake.
In fact I will likely be doing this PSM on vs off tests tomorrow at the track, if I'm able to get some video I will upload it.
Jun 3, 2008 12:59:24 PM
- cibergypsy
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Carlos from Spain
Re: Question about PSM and understeer
Quote:
Carlos from Spain said:Quote:
Silver Bullet said:Under and oversteer happen under different circumstances, so how PSM handles one dosen't really influence the other.
PSM doesn't cause understeer; believe it or not, it actually helps correct it by doing what I outlined above.
It does because when the car tends to understeer (coming in too fast into a corner for example) the PSM will correct it but if its overwhealming it will understeer regardless of PSM. However, if the car is in another situation were oversteer is induced (too much throttle or too early on the exit of a corner or trailbraking into a corner for example), PSM again will correct it but if its if its overwhealming, you will not oversteer however, PSM will induce understeer so that if it goes, at least it doesn't go in oversteer since that would be much more dangerous because you spin.
So while PSM helps correct under and oversteer, if it can't it will only allow one to occur for safety reasons.
For example, there is ice or mud in a corner at the track and you floor violently the throttle at mid corner. Without PSM in a RWD car you will instantly go into oversteer and likely spin. Yet if you try this with PSM "on" you will not oversteer, you will always run wide with understeer no matter what, time and time again. You won't spin, you simply let off the throttle, open up the steering angle a bit and regain control. Thats the PSM inducing understeer rather than allowing you to spin. Thats why with PSM all you notince when you loose traction is understeer. Unless you activatre the sport button in sport chrono cars, in that case there is a significant amount of oversteer allowed and PSM is much harder to kick in, usually not at all even at the track unless you make a mistake.
In fact I will likely be doing this PSM on vs off tests tomorrow at the track, if I'm able to get some video I will upload it.
Carlos, aquí tienes a un aficionado que estará esperando ansiosamente tus vídeos en la pista. Gracias.
Jun 3, 2008 1:46:16 PM
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Carlos from Spain
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Jun 4, 2008 2:33:41 AM
- 996toomey
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Carlos from Spain
Re: Question about PSM and understeer
I leave my button on and it never intercedes unless I make a major mistake where I would probably spin without PSM on.
If you are driving correctly and want to reduce understeer and help turn in consider changing front lower control arms and putting a more aggressive alignment on the car.
I have done this as well as rear toe links and my car is very balanced and will oversteer, understeer or turn in very well based on throttle input.
If you are driving correctly and want to reduce understeer and help turn in consider changing front lower control arms and putting a more aggressive alignment on the car.
I have done this as well as rear toe links and my car is very balanced and will oversteer, understeer or turn in very well based on throttle input.
Jun 4, 2008 3:41:18 AM
- cibergypsy
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Carlos from Spain
Re: Question about PSM and understeer
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Carlos from Spain said:Quote:
cibergypsy said:Carlos, aquí tienes a un aficionado que estará esperando ansiosamente tus vídeos en la pista. Gracias.
Thank you ciberypsy, that is perfect spanish, is it your mother tongue?
Yes, it is indeed my vernacular. Thanks for the compliment!
Jun 5, 2008 7:12:13 AM
- rantanplan
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Re: Question about PSM and understeer
Quote:
rantanplan said:
Carrera S oversteering...
you can see some nice oversteering when clicking the link above...
Jun 5, 2008 7:00:44 PM
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Carlos from Spain
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Re: Question about PSM and understeer
I'm back. I didn't have a change to make any videos from the inside, and those I have from the outside do not ilustrate the point. I had a chance to experiment in a tight tecnical track with the various models of the line up from a Cayman to a 997TT.
My personal objective was to develop more that sensitivety at dancing at the edge of the grip without loosing it through smoothness of the controls (throttle-steer-brake) through the various combinations of curves of the track. So I would force some mistakes and test and try different approaches. At first until getting used to each car's dinamics and grip I used PSM on, when I induced oversteer the car either went wide or if the overteer was severe and throught throttle (some parts of the track were intentionally very wet) the PSM would would just drop the car dead were it was, very annoying feeling BTM. So those would be the two reactions I would get with PSM upon inducing oversteer (I did it through lift-off oversteer coming into the curve, or throttle oversteer coming out of the curve)
Then later once familiar with the grip and the cars I switched the PSM OFF. Mainly because PSM does not let you learn from your mistakes, it takes it over from you quickly and thats it. Wereas with PSM off you can encounter all sorts of situations and you learn to deal with them and avoid them more and more as you get smoother and more sensitive.
The 997TT was the toughest because of the lag, and the fact that it was a Tip. The throttle delay did not allow you to aplly exactly the amioun you wnat and when you wanted it so you found yourself with times were you needed just a blip (like in between an "S" curves) and you didn't get it, or were you got none to too much all of a sudden out of a curve were you needed less and oversteered. There was a Carrera 2 manual with worn rears that was the most fun of all to drive, it was the sportiest character and more "alive". The fastest around this very tight and tecnical track was the 997C4S because it was the easiest to drive at the edge, got the power quickly to the ground (short gears track) and was easiest to control, not as much fun but safer and controlable reaction in this type of track. Cayman was very balanced and neutral chasis, no flaws at all, but lacked power, and also wasn't as fun to drive as the rear engined brother IMO.
I'll see if I can post some pictures in another thread next week and maybe some videos. Specially one from someone I cannot mention but... ever seen a two ton Cayenne GTS drifting through the corners with the tires screaming?
My personal objective was to develop more that sensitivety at dancing at the edge of the grip without loosing it through smoothness of the controls (throttle-steer-brake) through the various combinations of curves of the track. So I would force some mistakes and test and try different approaches. At first until getting used to each car's dinamics and grip I used PSM on, when I induced oversteer the car either went wide or if the overteer was severe and throught throttle (some parts of the track were intentionally very wet) the PSM would would just drop the car dead were it was, very annoying feeling BTM. So those would be the two reactions I would get with PSM upon inducing oversteer (I did it through lift-off oversteer coming into the curve, or throttle oversteer coming out of the curve)
Then later once familiar with the grip and the cars I switched the PSM OFF. Mainly because PSM does not let you learn from your mistakes, it takes it over from you quickly and thats it. Wereas with PSM off you can encounter all sorts of situations and you learn to deal with them and avoid them more and more as you get smoother and more sensitive.
The 997TT was the toughest because of the lag, and the fact that it was a Tip. The throttle delay did not allow you to aplly exactly the amioun you wnat and when you wanted it so you found yourself with times were you needed just a blip (like in between an "S" curves) and you didn't get it, or were you got none to too much all of a sudden out of a curve were you needed less and oversteered. There was a Carrera 2 manual with worn rears that was the most fun of all to drive, it was the sportiest character and more "alive". The fastest around this very tight and tecnical track was the 997C4S because it was the easiest to drive at the edge, got the power quickly to the ground (short gears track) and was easiest to control, not as much fun but safer and controlable reaction in this type of track. Cayman was very balanced and neutral chasis, no flaws at all, but lacked power, and also wasn't as fun to drive as the rear engined brother IMO.
I'll see if I can post some pictures in another thread next week and maybe some videos. Specially one from someone I cannot mention but... ever seen a two ton Cayenne GTS drifting through the corners with the tires screaming?
Jun 6, 2008 5:26:03 AM
- Silver Bullet
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Carlos from Spain
Re: Question about PSM and understeer
"if the car is in another situation were oversteer is induced (too much throttle or too early on the exit of a corner or trailbraking into a corner for example), PSM again will correct it but if its if its overwhealming, you will not oversteer however, PSM will induce understeer so that if it goes, at least it doesn't go in oversteer since that would be much more dangerous because you spin"
There is no opinion here or on any Porsche Forum that I value more than Carlos', but I have to disagree with this one.
What Carlos seems to be saying is that in an oversteer situation (real wheels slipping), PSM will correct by inducing understeer (front wheels slipping). All 4 wheels would then be slipping. That is, PSM would induce a 4 wheel drift, which is the most dangerous situation in driving.
In my experience, PSM is very good at dealing with oversteer and the correction, while it can be abrupt and unpleasant (especially to have control snatched away from you when you may be comfortable with the slide), has not lead me to feel any understeer.
Another word about over and understeer and PSM: unless you are a very very good driver, your lap times will almost certainly be better with PSM on than off. That is because both over and understeer slow you down, and PSM helps to manage them. If you are brave enough to push yourself with a timer, give it a try: most people will find exactly what I just wrote. Only the best (most experienced drivers) are faster with PSM off. Warning though: pushing yourself on a dry track with PSM of can be a dangerous thing to do. A slicked skid pad is the best place to demonstrate this because it can all happen at much slower speeds. There is a nice exercise at the Porsche Sport Driving School that illustrates this.
There is no opinion here or on any Porsche Forum that I value more than Carlos', but I have to disagree with this one.
What Carlos seems to be saying is that in an oversteer situation (real wheels slipping), PSM will correct by inducing understeer (front wheels slipping). All 4 wheels would then be slipping. That is, PSM would induce a 4 wheel drift, which is the most dangerous situation in driving.
In my experience, PSM is very good at dealing with oversteer and the correction, while it can be abrupt and unpleasant (especially to have control snatched away from you when you may be comfortable with the slide), has not lead me to feel any understeer.
Another word about over and understeer and PSM: unless you are a very very good driver, your lap times will almost certainly be better with PSM on than off. That is because both over and understeer slow you down, and PSM helps to manage them. If you are brave enough to push yourself with a timer, give it a try: most people will find exactly what I just wrote. Only the best (most experienced drivers) are faster with PSM off. Warning though: pushing yourself on a dry track with PSM of can be a dangerous thing to do. A slicked skid pad is the best place to demonstrate this because it can all happen at much slower speeds. There is a nice exercise at the Porsche Sport Driving School that illustrates this.
Jun 6, 2008 8:45:02 AM
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ResB
- Rennteam Pro
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- Loc: Yorkshire, where roads are twisty... , United Kingdom
- Posts: 2858, Gallery
- Registered on: Jan 19, 2006
- Reply to: Silver Bullet
Re: Question about PSM and understeer
I will give it a go next time I'm on the track. I'm hoping that with PSM off, my times/experience of the track will be quicker/more involved. Having said this though, currently with PSM on, the car has not stepped out of line insofar as oversteer is concerned, perhaps because PSM allows the car to understeer more, so I wonder if I have more room in the corner before I feel the back end starting to go, therefore giving rise to better lap times. (Or at least keeping up with my mate 
)
On reflection I have to say, with PASM/Sport mode engaged I still had quite a bit of understeer, but the car did feel better particularly on exit from any bend.
I need to explore this topic a little more at the track and I'll log it with the performance box if I can get away with it. Should be interesting getting the results I'm sure.
)On reflection I have to say, with PASM/Sport mode engaged I still had quite a bit of understeer, but the car did feel better particularly on exit from any bend.
I need to explore this topic a little more at the track and I'll log it with the performance box if I can get away with it. Should be interesting getting the results I'm sure.
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