PSM and autocrossing the boxster S
12-30-2002 | 11:01 PM
#16
Instructor
Joined: May 2002
Posts: 233
Likes: 0
From: Toronto, Canada
As far as I know, PSM does NOT interfere with the antilock brake function at all, they are separate systems, even though PSM accesses the brakes to do its thing. Antilocks are always on! So when disabled, it will not interfere with any movements (even though it is still "watching and learning" as it were) at all. Yes, yaw is one of the motions it will react to.
I understand PSM will invoke itself, even when turned off, when a set of extreme parameters are exceeded but I have never been there and I suspect not many will. The temporaryness of turning it off is really a function of the ignition. It re-engages when the car is started so you have to turn it off every time.
Quite frankly, I rarely experience it, but the reason I am so avid a fan is a few month ago, on a cool and damp morning, I hit a slippery spot on a turn and was heading for the curb, with no hope... then PSM stepped in and saved my 18" Turbo rim. Is it a good thing? You betcha!
I understand PSM will invoke itself, even when turned off, when a set of extreme parameters are exceeded but I have never been there and I suspect not many will. The temporaryness of turning it off is really a function of the ignition. It re-engages when the car is started so you have to turn it off every time.
Quite frankly, I rarely experience it, but the reason I am so avid a fan is a few month ago, on a cool and damp morning, I hit a slippery spot on a turn and was heading for the curb, with no hope... then PSM stepped in and saved my 18" Turbo rim. Is it a good thing? You betcha!
12-31-2002 | 10:24 AM
#18
Racer
Joined: May 2001
Posts: 284
Likes: 0
From: Seattle
[quote]Originally posted by craigg:
<strong>As far as I know, PSM does NOT interfere with the antilock brake function at all, they are separate systems, even though PSM accesses the brakes to do its thing. Antilocks are always on! So when disabled, it will not interfere with any movements (even though it is still "watching and learning" as it were) at all. Yes, yaw is one of the motions it will react to.</strong><hr></blockquote>
Craig, I don't think anyone suggested that ABS would be disabled when PSM is disabled. Horrors!
(I'm half joking, some folks would surely rather track their car without ABS.)
However, the rather sparse info I've found on PSM seems to indicate that it isn't completely disabled when disabled. E.g., Porsche says of PSM on the 911:
[quote]<strong>the [PSM] system can also be disabled, leaving only the automatic brake differential in place.</strong><hr></blockquote>
Meaning that PSM is not completely disabled. (ABD is not ABS.)
I've also heard that under braking some of PSM's higher functions wake up, but I may be confusing that with another system. My quest for info continues...
Curt
<strong>As far as I know, PSM does NOT interfere with the antilock brake function at all, they are separate systems, even though PSM accesses the brakes to do its thing. Antilocks are always on! So when disabled, it will not interfere with any movements (even though it is still "watching and learning" as it were) at all. Yes, yaw is one of the motions it will react to.</strong><hr></blockquote>
Craig, I don't think anyone suggested that ABS would be disabled when PSM is disabled. Horrors!
(I'm half joking, some folks would surely rather track their car without ABS.)However, the rather sparse info I've found on PSM seems to indicate that it isn't completely disabled when disabled. E.g., Porsche says of PSM on the 911:
[quote]<strong>the [PSM] system can also be disabled, leaving only the automatic brake differential in place.</strong><hr></blockquote>
Meaning that PSM is not completely disabled. (ABD is not ABS.)
I've also heard that under braking some of PSM's higher functions wake up, but I may be confusing that with another system. My quest for info continues...
Curt
01-04-2003 | 10:36 PM
#19
Thread Starter
Rennlist Member
Joined: Jul 2001
Posts: 1,723
Likes: 52
From: USA
Thanks to all who responded - I'm a little more confused now. The original intent of my question was "PSM in autocrossing." Yes I am a novice but I would like to get more of a "seat of the pants" feel of car control. I agree that PSM would be good to have for road use, it's really not that expensive. My understanding is that PSM comes on by itself under heavy braking or when the car is really out of shape - even when you have turned it off! This is why I think it might not be useful in autocrossing. I have an E36 M3, when you turn off traction control, it stays off no matter what. Is this not the case with Porsche? How does the Boxster manage wheel slippage without PSM, it does not have a limited slip differential as far as I know like the M3. As you can see I am still confused. I am delaying my Boxster S purchase till I get some more info from you guys. Thanks
01-05-2003 | 11:50 AM
#21
Addict
Rennlist Member
Rennlist Member
Joined: Nov 2002
Posts: 3,802
Likes: 0
Riz,
Read the posts again, then buy the Boxster S with the PSM and experiment with it 'til your hearts content at autocrosses. You'll be be faster with it untill you learn how to be faster without it , if ever.
Enjoy and have no regrets
Read the posts again, then buy the Boxster S with the PSM and experiment with it 'til your hearts content at autocrosses. You'll be be faster with it untill you learn how to be faster without it , if ever.
Enjoy and have no regrets
01-29-2003 | 05:25 PM
#22
Track Day
Joined: Nov 2002
Posts: 17
Likes: 0
From: Cheshire, UK
The website says it all.
Both Boxster models are available with Porsche Stability Management (PSM). This optional driver aid provides added control in difficult road situations. To do that, the system uses a series of sensors to monitor direction, speed, yaw velocity (rotation around vertical axis) and lateral acceleration.
PSM then uses these values to calculate the actual direction of travel. If the car begins to oversteer or understeer, PSM applies selective braking on individual wheels to keep the car on line. If braking isn't enough, PSM can access engine management via the engine drag torque control system. Ignition, fuel injection and throttle position can then be modified to stabilise the car at an optimum speed. PSM can also compensate for loss of stability caused by sudden mid-corner changes in relative wheel loadings. Traction is also significantly improved on even the most inconsistent road surfaces. In critical situations, PSM provides that extra security which can sometimes make all the difference. The agility of the car is fully maintained, enabling a more dynamic ride than that offered by comparable systems. For those occasions where you'd rather enjoy your Boxster unassisted, the system can also be disabled.
I gave a friend (ex racer) a shot of the boxster S at work, slightly damp road going on to the motorway accelerating hard hit a cnage of camber big tailslide he over corrects and just catchs the armco barrier, £2500 poundsworth of damage.
I've got it on the M3 and its a god send particularly after a long day at work. There has been quite a few times I've wished I had it on the Boxster, when I've been tired, its been wet(and or dark) and I am having to press on to get to another client or to get home on unfamiliar winding roads.
This car doesn't have PSM, but the new one arriving in March does.
I agree that it also can give you more confidence on the track, I put it on in the M3 if the conditions get slippy. I haven't taken the Boxster to the track because it doesn't have it <img border="0" title="" alt="[Eek!]" src="eek.gif" /> .
Even doing a few laps with it on in the dry and noticing when the PSM is intervening gives you an idea where you need to smooth out to maintain grip and traction, its a good learning tool as well as a safety feature.
On this day it was Icy to start (-4C) and i had traction control on till about 11.00 am, you can still see the frost and ice at the side.
<img src="http://www.geocities.com/mrjumjum/OultonParkdec2002049.jpg" alt=" - " />
Both Boxster models are available with Porsche Stability Management (PSM). This optional driver aid provides added control in difficult road situations. To do that, the system uses a series of sensors to monitor direction, speed, yaw velocity (rotation around vertical axis) and lateral acceleration.
PSM then uses these values to calculate the actual direction of travel. If the car begins to oversteer or understeer, PSM applies selective braking on individual wheels to keep the car on line. If braking isn't enough, PSM can access engine management via the engine drag torque control system. Ignition, fuel injection and throttle position can then be modified to stabilise the car at an optimum speed. PSM can also compensate for loss of stability caused by sudden mid-corner changes in relative wheel loadings. Traction is also significantly improved on even the most inconsistent road surfaces. In critical situations, PSM provides that extra security which can sometimes make all the difference. The agility of the car is fully maintained, enabling a more dynamic ride than that offered by comparable systems. For those occasions where you'd rather enjoy your Boxster unassisted, the system can also be disabled.
I gave a friend (ex racer) a shot of the boxster S at work, slightly damp road going on to the motorway accelerating hard hit a cnage of camber big tailslide he over corrects and just catchs the armco barrier, £2500 poundsworth of damage.
I've got it on the M3 and its a god send particularly after a long day at work. There has been quite a few times I've wished I had it on the Boxster, when I've been tired, its been wet(and or dark) and I am having to press on to get to another client or to get home on unfamiliar winding roads.
This car doesn't have PSM, but the new one arriving in March does.
I agree that it also can give you more confidence on the track, I put it on in the M3 if the conditions get slippy. I haven't taken the Boxster to the track because it doesn't have it <img border="0" title="" alt="[Eek!]" src="eek.gif" /> .
Even doing a few laps with it on in the dry and noticing when the PSM is intervening gives you an idea where you need to smooth out to maintain grip and traction, its a good learning tool as well as a safety feature.
On this day it was Icy to start (-4C) and i had traction control on till about 11.00 am, you can still see the frost and ice at the side.
<img src="http://www.geocities.com/mrjumjum/OultonParkdec2002049.jpg" alt=" - " />
01-31-2003 | 11:12 PM
#23
AutoX
Joined: Jan 2003
Posts: 12
Likes: 0
From: Mission Viejo, CA
I've left PSM on at several track events, and except for some slow 2nd gear tight corners, I've never felt PSM intervene. I don't think I'm any faster or slower with it off or on. However, it does help to keep me on the pavement. Sometimes I wish my Viper had it. It sure makes me more confident in the 4th gear sweepers.
Since autocross is mostly 2nd gear tight stuff I think you might be faster with PSM turned off. Not sure as I'm mostly a track guy, not a cone dodger <img border="0" title="" alt="[Wink]" src="wink.gif" />
PSM is invaluable on the road IMHO. I've been on several canyon runs and have come around a corner to discover a rock in the road or some loose gravel. It's nice to have PSM's ability to accept a sudden steering movement or "gasp" braking in mid-turn to avoid the obstacle.
Porsche's PSM is unlike any I've driven. It really allows a lot of slip before it says "okay, you had enough fun" and starts to reel you back in. I get a kick out of playing around with it. You can turn it off and it stays off but comes back on temporarily when you brake, then turns itself back off again. I think the logic is that if you're cornering at the limit of adhesion and you hit the brakes, you're either really stupid, or you've encountered a panic situation (i.e. rock in the road, see above) and PSM is there to save your rear.
I came close to not ordering it. When I asked my salesperson, he said "well, look at it this way, it only has to save you once..." and it has more than paid for itself. Made sense. I suppose if it was a "track only" car I'd skip PSM.
Since autocross is mostly 2nd gear tight stuff I think you might be faster with PSM turned off. Not sure as I'm mostly a track guy, not a cone dodger <img border="0" title="" alt="[Wink]" src="wink.gif" />
PSM is invaluable on the road IMHO. I've been on several canyon runs and have come around a corner to discover a rock in the road or some loose gravel. It's nice to have PSM's ability to accept a sudden steering movement or "gasp" braking in mid-turn to avoid the obstacle.
Porsche's PSM is unlike any I've driven. It really allows a lot of slip before it says "okay, you had enough fun" and starts to reel you back in. I get a kick out of playing around with it. You can turn it off and it stays off but comes back on temporarily when you brake, then turns itself back off again. I think the logic is that if you're cornering at the limit of adhesion and you hit the brakes, you're either really stupid, or you've encountered a panic situation (i.e. rock in the road, see above) and PSM is there to save your rear.
I came close to not ordering it. When I asked my salesperson, he said "well, look at it this way, it only has to save you once..." and it has more than paid for itself. Made sense. I suppose if it was a "track only" car I'd skip PSM.
