PSM vs TC
04-07-2009, 08:50 PM
#16
Ironman 140.6
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The 986 was available with Traction Control on some of the model years. If memory serves the system was defeatable via a dashboard switch and incorporated both and ABD and retarded the throttle via the ecu to limit rear wheel spin.
PSM has traction control in it's functionality, but also adds throttle position sensors, steering sensors, and yaw sensors that can brake individual wheels to control rear wheel spin and also correct impending spins
http://www.panix.com/clay/cayenne/PSM.html
To the OP I would say this;
- It seems from your post that you are concerned with the Boxster having some difficult handling characteristics due to it's mid-engine design. In fact the Boxster's basic handling is very good at the limit (pretty benign actually) and it is not at all spin prone when compared with other sports cars that can be much more of a handful (the Honda S2000 comes to mind as an example). I do not have it (PSM) on my Boxster and I have never missed it. In fact if you gave me the choice to drive a PSM car on all season tires in the snow, vs. a Boxster w/o PSM or TC on snow tires in the snow I would not even hesitate to choose the car on snow tires.
(for the record, I have PSM on my Carrera, but no PSM (or TC) on my Boxster.)
Good Luck with your search!!
PSM has traction control in it's functionality, but also adds throttle position sensors, steering sensors, and yaw sensors that can brake individual wheels to control rear wheel spin and also correct impending spins
http://www.panix.com/clay/cayenne/PSM.html
To the OP I would say this;
- It seems from your post that you are concerned with the Boxster having some difficult handling characteristics due to it's mid-engine design. In fact the Boxster's basic handling is very good at the limit (pretty benign actually) and it is not at all spin prone when compared with other sports cars that can be much more of a handful (the Honda S2000 comes to mind as an example). I do not have it (PSM) on my Boxster and I have never missed it. In fact if you gave me the choice to drive a PSM car on all season tires in the snow, vs. a Boxster w/o PSM or TC on snow tires in the snow I would not even hesitate to choose the car on snow tires.
(for the record, I have PSM on my Carrera, but no PSM (or TC) on my Boxster.)
Good Luck with your search!!
04-07-2009, 08:51 PM
#17
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Bet,
The only times the TC activates while I'm driving is under hard acceleration on wet roads, usually while turning or moderate acceleration on snowy/ice. Usually the inside rear wheel will lose traction first and the TC will apply brakes to that wheel. If you attempt to drift the rear of the car and brake both rear tires lose the TC will cut power IIRC. You can turn off TC and drift the rear of the car into an oversteer and the TC will not engage unless you let off the accelerator or apply the brakes when it "thinks" you are in over your head. The car feels like it has run out of gas momentarily but the quickly resumes power, hopefully you pointed in the right direction by then.
TCs usefulness for me is mostly in the winter and at relatively low speeds, but it did kick in unexpectedly on an off camber curve where water had pooled. In most cases I have to intentionally push the car to get the TC to engage on dry roads.
Here is a quote from European Car Magazine.
"Our Boxster S was equipped with Porsche's optional traction control ($870), an electronic aid that blends Automatic Brake Differential (ABD) and Anti-Slip Control (ASC). If ABD detects a specific difference in speed between the rear wheels, it applies the brakes to the faster wheel to restore traction. If both wheels are spinning, ASC reduces the engine's power. Aware the electronic safety police were watching over him, the driver was under the assumption the Boxster S was correcting his mistakes--while he made many, the system never even came into use (he wasn't even close). When I turned the traction control off, he slowed down significantly, certain we'd go flying off into space. We didn't.
Pushing the Boxster S to the limit is not for the faint of heart. If you do manage to activate the traction control on a dry road, you're either being chased by terrorists or have done something so stupid you deserve a black flag and a boot to the head. Would I get the TC option? No, but I would get it for the wife and hide the switch so she could never turn it off."
And here is a quote from Dennis Pendersen's website describing traction control and how it works.
http://www.rahul.net/dennisp/boxster...ions.shtml#p37
"P37 Traction Control
This option consists of two systems; both accomplished through enhancements to the ABS system. The first is the Active Brake Differential ("ABD") which is always on at speeds below about 60 mph and is sort of like a conventional "limited slip." The other is the Anti-Slip Regulation ("ASR") which can be turned off with a button but is otherwise always on. Somehow it has become accepted by a lot of Boxster people that P37 is useless. Nothing could be further from the truth. This option is quite useful for people who drive their Boxsters the way Porsche intended them to be driven! Here's what they do:
ABD simply applies braking to the rear wheel on one side if it's spinning too fast compared with the other rear wheel. What's it good for?
Classic example: You park your car at the side of a country road. One rear wheel is on mud while the other is still on the pavement. When you try to get the car moving again, the wheel in the mud spins uselessly while the wheel on the pavement just sits there without contributing anything. You're stuck unless you can somehow find a tow-truck, or some rocks, branches, expensive leather jacket etc. to stick under the spinning wheel for extra traction. Frustrating, huh?
With a limited slip, or ABD in this case, you wouldn't need to worry: As long as one wheel has traction you'll be able to accelerate away from your poorly-chosen parking spot.
ASR comes into play if the ABD isn't enough for the conditions. ASR is much more intrusive and reduces engine power (to the rear wheels of course) when they're both spinning faster than the front wheels. That way it keeps you from spinning the rear wheels uselessly. But that prevents those fun "smoky burnouts" too! Still, it's cool because it allows you to use the car's power more safely and predictably even in heavy rain, gravel, snow etc. Granted, if you're a good driver who pays attention to the car and knows the car's limits on any given surface, you can just turn off ASR (or not order it in the first place) and just back off the throttle yourself instead of relying on the ASR to do it for you. But most of us aren't perfect, and that's where ASR is a major benefit.
I wouldn't consider P37 essential, especially if you always drive within the car's limits. That is, if you don't usually get wheel-spin in your present car, you probably won't ever need this option. But if you often stomp on the gas, even when there's gravel, rain, ice, oil, or whatever, on the road surface, then this might just be the ticket to help keep you out of trouble.
For people who autocross or otherwise race their cars P37 is a "must have" in my opinion, because the ABD gives you more traction when you accelerate out of turns. Many Boxster people mistakenly assume that because the Boxster has more weight on the rear wheels than on the front there is enough traction to prevent wheelspin under power. That is not true! Even with P37, I can break both tires loose under hard acceleration. Yes, I do have to push the car pretty hard to do so, but it is possible, and easier than many think. The fact that I break both wheels loose shows that ABD works great, and does the job of distributing torque to both wheels for maximum traction.
But turn the "TC" button off before your runs, or else the ASR will kick in and slow you down. I believe that's because the ASR control software is written so that there's always a "margin for error" added in. In other words, the ASR backs off power enough to stop wheel spin, then backs off the power a little more so that it won't be caught by surprise in case the traction is reduced even further. That lost power is returned to you after a certain amount of time has elapsed, but until that happens the ASR has slowed you down. See "My Boxster Tests" page for some interesting results comparing 0 to 60 acceleration runs with TC on and off. Also, ASR has some annoying "features:" ASR makes it more difficult to "steer with the throttle," in part because it has a maddening lag between when wheel-spin starts and when the ASR kicks in. And when ASR does kick in it feels like you've just run out of gas! I wish the ASR were more subtle. My wife's BMW has much better traction control, and Porsche should just copy it!"
The only times the TC activates while I'm driving is under hard acceleration on wet roads, usually while turning or moderate acceleration on snowy/ice. Usually the inside rear wheel will lose traction first and the TC will apply brakes to that wheel. If you attempt to drift the rear of the car and brake both rear tires lose the TC will cut power IIRC. You can turn off TC and drift the rear of the car into an oversteer and the TC will not engage unless you let off the accelerator or apply the brakes when it "thinks" you are in over your head. The car feels like it has run out of gas momentarily but the quickly resumes power, hopefully you pointed in the right direction by then.
TCs usefulness for me is mostly in the winter and at relatively low speeds, but it did kick in unexpectedly on an off camber curve where water had pooled. In most cases I have to intentionally push the car to get the TC to engage on dry roads.
Here is a quote from European Car Magazine.
"Our Boxster S was equipped with Porsche's optional traction control ($870), an electronic aid that blends Automatic Brake Differential (ABD) and Anti-Slip Control (ASC). If ABD detects a specific difference in speed between the rear wheels, it applies the brakes to the faster wheel to restore traction. If both wheels are spinning, ASC reduces the engine's power. Aware the electronic safety police were watching over him, the driver was under the assumption the Boxster S was correcting his mistakes--while he made many, the system never even came into use (he wasn't even close). When I turned the traction control off, he slowed down significantly, certain we'd go flying off into space. We didn't.
Pushing the Boxster S to the limit is not for the faint of heart. If you do manage to activate the traction control on a dry road, you're either being chased by terrorists or have done something so stupid you deserve a black flag and a boot to the head. Would I get the TC option? No, but I would get it for the wife and hide the switch so she could never turn it off."
And here is a quote from Dennis Pendersen's website describing traction control and how it works.
http://www.rahul.net/dennisp/boxster...ions.shtml#p37
"P37 Traction Control
This option consists of two systems; both accomplished through enhancements to the ABS system. The first is the Active Brake Differential ("ABD") which is always on at speeds below about 60 mph and is sort of like a conventional "limited slip." The other is the Anti-Slip Regulation ("ASR") which can be turned off with a button but is otherwise always on. Somehow it has become accepted by a lot of Boxster people that P37 is useless. Nothing could be further from the truth. This option is quite useful for people who drive their Boxsters the way Porsche intended them to be driven! Here's what they do:
ABD simply applies braking to the rear wheel on one side if it's spinning too fast compared with the other rear wheel. What's it good for?
Classic example: You park your car at the side of a country road. One rear wheel is on mud while the other is still on the pavement. When you try to get the car moving again, the wheel in the mud spins uselessly while the wheel on the pavement just sits there without contributing anything. You're stuck unless you can somehow find a tow-truck, or some rocks, branches, expensive leather jacket etc. to stick under the spinning wheel for extra traction. Frustrating, huh?
With a limited slip, or ABD in this case, you wouldn't need to worry: As long as one wheel has traction you'll be able to accelerate away from your poorly-chosen parking spot.
ASR comes into play if the ABD isn't enough for the conditions. ASR is much more intrusive and reduces engine power (to the rear wheels of course) when they're both spinning faster than the front wheels. That way it keeps you from spinning the rear wheels uselessly. But that prevents those fun "smoky burnouts" too! Still, it's cool because it allows you to use the car's power more safely and predictably even in heavy rain, gravel, snow etc. Granted, if you're a good driver who pays attention to the car and knows the car's limits on any given surface, you can just turn off ASR (or not order it in the first place) and just back off the throttle yourself instead of relying on the ASR to do it for you. But most of us aren't perfect, and that's where ASR is a major benefit.
I wouldn't consider P37 essential, especially if you always drive within the car's limits. That is, if you don't usually get wheel-spin in your present car, you probably won't ever need this option. But if you often stomp on the gas, even when there's gravel, rain, ice, oil, or whatever, on the road surface, then this might just be the ticket to help keep you out of trouble.
For people who autocross or otherwise race their cars P37 is a "must have" in my opinion, because the ABD gives you more traction when you accelerate out of turns. Many Boxster people mistakenly assume that because the Boxster has more weight on the rear wheels than on the front there is enough traction to prevent wheelspin under power. That is not true! Even with P37, I can break both tires loose under hard acceleration. Yes, I do have to push the car pretty hard to do so, but it is possible, and easier than many think. The fact that I break both wheels loose shows that ABD works great, and does the job of distributing torque to both wheels for maximum traction.
But turn the "TC" button off before your runs, or else the ASR will kick in and slow you down. I believe that's because the ASR control software is written so that there's always a "margin for error" added in. In other words, the ASR backs off power enough to stop wheel spin, then backs off the power a little more so that it won't be caught by surprise in case the traction is reduced even further. That lost power is returned to you after a certain amount of time has elapsed, but until that happens the ASR has slowed you down. See "My Boxster Tests" page for some interesting results comparing 0 to 60 acceleration runs with TC on and off. Also, ASR has some annoying "features:" ASR makes it more difficult to "steer with the throttle," in part because it has a maddening lag between when wheel-spin starts and when the ASR kicks in. And when ASR does kick in it feels like you've just run out of gas! I wish the ASR were more subtle. My wife's BMW has much better traction control, and Porsche should just copy it!"
04-07-2009, 09:12 PM
#18
Drifting
Thread Starter
Aron 
Fantastic articles. Just want I really wanted to know. I think TC would be sufficient for my concerns. Thank you very much. If we were on one of those boards with rep points I would be submitting some points.
Ray, actually I don't have any fears of the handling of a mid-engine car like the Boxster...In fact owned a Boxster in 2000 and currently have a Cayman S (moved from a 996). I love the mid engine layout, quick turn-in and the fact it makes mediocre drivers look good
(like yours truly). However, I also know that with mid engine cars catching and correcting mistakes under adverse road conditions requires some skill and attention. This car is primarily going to be for my wife. Past experience says she doesn't always pay attention and then compound that with the fact she is use to driving a BMW 328i on a daily basis that has a HUGE nanny in DSC (I have seen her activate that system many a times) and I am fearful that she will just punch it and go and think nothing about it (which she can do all day long in the BMW and never get into trouble). I want as much a safety net under less than ideal road conditions that is reasonable to prevent possible issues. Sure the answer should be she should pay attention better but I digress...
Fantastic articles. Just want I really wanted to know. I think TC would be sufficient for my concerns. Thank you very much. If we were on one of those boards with rep points I would be submitting some points.Ray, actually I don't have any fears of the handling of a mid-engine car like the Boxster...In fact owned a Boxster in 2000 and currently have a Cayman S (moved from a 996). I love the mid engine layout, quick turn-in and the fact it makes mediocre drivers look good
(like yours truly). However, I also know that with mid engine cars catching and correcting mistakes under adverse road conditions requires some skill and attention. This car is primarily going to be for my wife. Past experience says she doesn't always pay attention and then compound that with the fact she is use to driving a BMW 328i on a daily basis that has a HUGE nanny in DSC (I have seen her activate that system many a times) and I am fearful that she will just punch it and go and think nothing about it (which she can do all day long in the BMW and never get into trouble). I want as much a safety net under less than ideal road conditions that is reasonable to prevent possible issues. Sure the answer should be she should pay attention better but I digress...
04-08-2009, 01:27 PM
#19
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Brian,
I think you are justified in worrying about your wife in a Boxster. Regardless of how many nannies the car has, it is a car that requires driver involvement at all times. That's not to say that its on a knife edge of instability but an inattentive driver can get in more trouble in the Box than a 328i. If she is activating the DSC in the BMW and is unaware of it then any true sports car is not for her. Get her a newer BMW iX series, a Volvo C70 or a Subaru and she will get home safe and sound.
I think you are justified in worrying about your wife in a Boxster. Regardless of how many nannies the car has, it is a car that requires driver involvement at all times. That's not to say that its on a knife edge of instability but an inattentive driver can get in more trouble in the Box than a 328i. If she is activating the DSC in the BMW and is unaware of it then any true sports car is not for her. Get her a newer BMW iX series, a Volvo C70 or a Subaru and she will get home safe and sound.
04-08-2009, 07:03 PM
#20
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My oversimplified translation:
TC (traction control) - gets you going
PSM (porsche stability management) - keeps you on course
By '10 or so, all cars sold in the US are to have some form of stability management.. and of course it makes it easier to "text" while driving
TC (traction control) - gets you going
PSM (porsche stability management) - keeps you on course
By '10 or so, all cars sold in the US are to have some form of stability management.. and of course it makes it easier to "text" while driving
04-15-2009, 03:06 PM
#21
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One thing I don't like is once I've done that, I stand on the gas to accelerate out of the corner... and get nothing. time passes. Frustratingly long time passes. Then FINALLY, after maybe a half second or so, PSM lets go and the engine roars back to life. What, exactly, is PSM doing while I'm tossing my car around like this?
(Not that I'm saying that works, obviously...)
04-17-2009, 12:59 AM
#22
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Just a quick word on the car's propensity to spin,
I pretty much learned how to drive properly in a 986 Boxster. Before my '00 986, I had never driven a high performance car. I did some DE events and really did some stupid things while learning how to drive properly. The car never let me down and never once has it spun, despite me driving very badly at first.
I've just gotten back to the Boxster via my '04 and I'm back on the track again. My first track day with the new car, I did a ride along with a great instructor from SCCA, the first thing he said was "you can go into a corner in this thing backwards and still come out OK, you CANNOT do it wrong in a Boxster." That made me laugh. Seriously, the car is so stable and composed at the limits that I think that PSM would be a real shame. I have PSM on my Cayenne, but that's an SUV, totally different story. I can say from my Cayenne experience that PSM is great, but is definately a buzzkill. When it steps in, all the fun stops. The other problem is that it is way more conservative than I am so it kicks in way before I think it really needs to. In a ginormous SUV, this is a very good thing. In a Boxster?? Nah.
How about you go ahead, buy the Boxster for your wife and give her some DE days as a "new car present."? Knowing how to drive properly is better insurance than any electronic doodad.
A
PS: That being said, the TC sounds nice for snow. I'm in NorCal so we don't have to worry about such things...
I pretty much learned how to drive properly in a 986 Boxster. Before my '00 986, I had never driven a high performance car. I did some DE events and really did some stupid things while learning how to drive properly. The car never let me down and never once has it spun, despite me driving very badly at first.
I've just gotten back to the Boxster via my '04 and I'm back on the track again. My first track day with the new car, I did a ride along with a great instructor from SCCA, the first thing he said was "you can go into a corner in this thing backwards and still come out OK, you CANNOT do it wrong in a Boxster." That made me laugh. Seriously, the car is so stable and composed at the limits that I think that PSM would be a real shame. I have PSM on my Cayenne, but that's an SUV, totally different story. I can say from my Cayenne experience that PSM is great, but is definately a buzzkill. When it steps in, all the fun stops. The other problem is that it is way more conservative than I am so it kicks in way before I think it really needs to. In a ginormous SUV, this is a very good thing. In a Boxster?? Nah.
How about you go ahead, buy the Boxster for your wife and give her some DE days as a "new car present."? Knowing how to drive properly is better insurance than any electronic doodad.
A
PS: That being said, the TC sounds nice for snow. I'm in NorCal so we don't have to worry about such things...
04-19-2009, 04:53 PM
#24
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04-28-2009, 04:16 PM
#25
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I will disagree a bit with the TC comment. We've got it on our 2000 S, and it does interfere at speed if you apply too much throttle in a corner. Noticeable on the track in certain turns. If you try to power too much coming out of a corner, the light flashes, and the car mysteriously slows. I believe TC is utilizing the ABS system to clamp the brakes to stop the inside wheel from spinning. I'm not certain if any throttle modulcation is occuring, but I don't think so. As mentioned earlier, TC tries to mimic LSD by using brakes to slow the spinning wheel, whether from a start on slippery surface, or powering thru a corner.
04-28-2009, 04:39 PM
#26
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TC can also close the throttle back up, and with electronic throttle control you'll never feel it. The car just doesn't go. Kinda like you're describing?
