Does PSM fight understeer? If so, how?
12-31-2009, 10:29 AM
#1
Weathergirl
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Does PSM fight understeer? If so, how?
Was driving to work on 2" of fresh snow and mostly empty roads, so I was trying to familiarize myself with what the traction control and PSM will do in various circumstances.
It's really great at managing braking while turning and keeping everything as straight as possible. Power oversteer was limited pretty abrutptly too.
One thing that was strange, though: entering a tight turn under power, the front end would push wide, and the PSM didn't seem to do anything to stop it. Shouldn't it be braking the inside rear or something?
It's really great at managing braking while turning and keeping everything as straight as possible. Power oversteer was limited pretty abrutptly too.
One thing that was strange, though: entering a tight turn under power, the front end would push wide, and the PSM didn't seem to do anything to stop it. Shouldn't it be braking the inside rear or something?
12-31-2009, 11:30 AM
#2
Rennlist Member
You need a certain amount of throttle input to get the PSM to do it's thing (at least that's what I've found).
Think about it - if you're coasting, or braking, and getting understeer, the most that the car can do is really ABS work: just release the brake at a specific wheel. But, under power, it can use the greater speed differential between the powered wheels and the wheels under braking to control the alignment of the car.
I was just playing in the snow, too.
Think about it - if you're coasting, or braking, and getting understeer, the most that the car can do is really ABS work: just release the brake at a specific wheel. But, under power, it can use the greater speed differential between the powered wheels and the wheels under braking to control the alignment of the car.
I was just playing in the snow, too.
12-31-2009, 12:25 PM
#3
Still plays with cars.
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PSM is supposed to brake the inside front wheel to cure understeer. Not sure why it did not work on snow.
12-31-2009, 08:21 PM
#4
Drifting
Was driving to work on 2" of fresh snow and mostly empty roads, so I was trying to familiarize myself with what the traction control and PSM will do in various circumstances.
It's really great at managing braking while turning and keeping everything as straight as possible. Power oversteer was limited pretty abrutptly too.
One thing that was strange, though: entering a tight turn under power, the front end would push wide, and the PSM didn't seem to do anything to stop it. Shouldn't it be braking the inside rear or something?
It's really great at managing braking while turning and keeping everything as straight as possible. Power oversteer was limited pretty abrutptly too.
One thing that was strange, though: entering a tight turn under power, the front end would push wide, and the PSM didn't seem to do anything to stop it. Shouldn't it be braking the inside rear or something?
Might be the key words.
Rear engine rear drive, what would you have the PSM do...??
The only thing the PSM might do is what early Porsche owners learned to NEVER do.
12-31-2009, 08:26 PM
#5
Drifting
The normal stability control reaction to understear is to instantly dethrottle the engine and brake both rear wheels. But that's not exactly a good idea in a rear engine rear drive Porsche.
12-31-2009, 09:13 PM
#6
Still plays with cars.
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Sorry guys, I must have been dreaming - PSM brakes the inside REAR wheel to counter understeer. For PSM to intervene, it gets input from the steering angle sensor (how far is the steering wheel turned) and lateral acceleration sensor. Comparing the two allows the system to determine whether the car is under or oversteering.
When I drive on a track (including ice tracks in winter) PSM is always off so I can't comment from experience. PSM makes pendulum turns impossible and that's half the fun of running on a snow/ice track!. I wonder if on a very slippery surface the lateral acceleration sensor did not provide enough difference between the steering angle and itself to intervene.
When I drive on a track (including ice tracks in winter) PSM is always off so I can't comment from experience. PSM makes pendulum turns impossible and that's half the fun of running on a snow/ice track!. I wonder if on a very slippery surface the lateral acceleration sensor did not provide enough difference between the steering angle and itself to intervene.
