What does PSM really do?
10-08-2007, 02:34 PM
#16
Racer
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Yes. From memory: if PSM is off and the car is not in sport mode then it comes back on when ABS is engaged for one wheel; in sport mode, PSM does not come back on until ABS is engaged for two wheels.
10-08-2007, 02:41 PM
#17
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My impression is that most of the people who say we should turn PSM off, have not actually driven a 997 to the point where it requires help from a stability management system. I suspect that most of them may be familiar with other similar systems, but not this one. My sense is that if you keep your car well balenced, PSM will not be the limiting factor in attaining low lap times. It's when you get things out of kilter that PSM steps in to help, and when it does, you'll most likely be very glad. I'd love to see a pro-level driver run laps with and without PSM. I'll guess that there would be no difference in times.
10-08-2007, 04:37 PM
#18
Burning Brakes
There are such comprehensive comments coming in about this I wonder if I may pose another related question which I raised a year ago and never had answered to my satisfaction:
When we turn the 'sport' function on, what exactly happens in the engine? I don't mean that ".....throttle response is sharper, etc..." but what is the engine combustion doing differently? Is the mixture enriched? Increased? And why, if this results in sharper performance, is the engine not programmed to operate like that all the time?
When we turn the 'sport' function on, what exactly happens in the engine? I don't mean that ".....throttle response is sharper, etc..." but what is the engine combustion doing differently? Is the mixture enriched? Increased? And why, if this results in sharper performance, is the engine not programmed to operate like that all the time?
10-08-2007, 04:56 PM
#20
Burning Brakes
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Sport "on" simply remaps the throttle to respond faster (more progressive actuation). The air/fuel mix does not change - that would destroy emissions compliance.
Sport "on" also raises the PSM activation threshold to allow more yaw/slip before activation. That's according to the 997 tech manual; no idea how to quantify the "relaxation effect". I do know that I can get the tail out further in the C4S when Sport is "on".
I find that the sharper throttle diminishes control; I'm more likely to prod the pedal with my toe when Sport is on, whilst Sport off works better with a conventional foot placement (heel flat against the pedal). So, one might venture that the sharper setting promotes bad driving posture... :-)
-d
Sport "on" also raises the PSM activation threshold to allow more yaw/slip before activation. That's according to the 997 tech manual; no idea how to quantify the "relaxation effect". I do know that I can get the tail out further in the C4S when Sport is "on".
I find that the sharper throttle diminishes control; I'm more likely to prod the pedal with my toe when Sport is on, whilst Sport off works better with a conventional foot placement (heel flat against the pedal). So, one might venture that the sharper setting promotes bad driving posture... :-)
-d
10-08-2007, 04:57 PM
#21
Burning Brakes
10-08-2007, 05:15 PM
#22
Rennlist Member
10-08-2007, 06:19 PM
#23
Unique Title
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This is a 997 forum though, and the system in these cars is quite different. It's much more compliant and hardly intrusive so long as you remain in control of the car. Sport Chrono allows the system to be relaxed further. PSM is just like time at the track: A tool to help people become better drivers. Like all tools, you haveto learn how it works and how to use it to use it well. Pay attention to when it activates and figure out why. If you can predict exactly when and why the system will intervene before you do something, then think about turning it off. Until then, well you get a lot more seat time if you don't wreck your ride.
I've heard a lot of people say they turn their stability control systems off because "they just slow me down". That vast majority of those guys ended up flatbedding their cars home after stuffing them into a wall. This isn't a hypothetical: Last summer at RA a guy bragged about how he turned the system off in his 350Z because it was only slowing him down and he totaled his car that afternoon. He wasn't hurt, but a little electronic help could have saved his car and his weekend. I've not seen him at the track since.
My experience has been that when I'm driving well, I never hear a peep from PSM on the street or at the track. I usually have to screw up pretty good to need its help, but then I'm glad I have it. I analyze my mistake, learn from it, and go for another lap.
10-08-2007, 06:22 PM
#24
Rennlist Member
There are such comprehensive comments coming in about this I wonder if I may pose another related question which I raised a year ago and never had answered to my satisfaction:
When we turn the 'sport' function on, what exactly happens in the engine? I don't mean that ".....throttle response is sharper, etc..." but what is the engine combustion doing differently? Is the mixture enriched? Increased? And why, if this results in sharper performance, is the engine not programmed to operate like that all the time?
When we turn the 'sport' function on, what exactly happens in the engine? I don't mean that ".....throttle response is sharper, etc..." but what is the engine combustion doing differently? Is the mixture enriched? Increased? And why, if this results in sharper performance, is the engine not programmed to operate like that all the time?
10-08-2007, 06:26 PM
#25
These debates are always the same. I have been trying to come up with a good way to address the problem, because it seems like people are talking "past" each other. In order to be a very good driver, you need two distinct skills.
First, you need to be able to drive the car right at the edge of the limit, and keep it there, lap after lap after lap. This will make you fast.
Second, you need to be able to catch the car if and when you momentarily exceed the limit. This will make you safe.
PSM will not interfere whatsoever with the former skill. PSM will prevent you from learning the latter skill. So long as you are always using PSM, you may not care. However, once you go from a PSM car to a non-PSM car, you need to realize that you may not have adequate experience with the lattter skill.
I hope this provides a more useful framework to discuss the problem.
I started track driving in a 996 with PSM. I never turned it off. I rarely had PSM activate. I had learned the former skill rather well, or perhaps I never really pushed close enough to the limit that it really mattered.
Then I bought a n/a 944 racecar that didn't even have PSM. Although I rarely spun, I was forced to learn the latter skill.
Now that I have a club coupe, I will leave PSM on if and when I take it to the track again. I have nothing to prove to anyone, and it definitely will not "slow me down"
First, you need to be able to drive the car right at the edge of the limit, and keep it there, lap after lap after lap. This will make you fast.
Second, you need to be able to catch the car if and when you momentarily exceed the limit. This will make you safe.
PSM will not interfere whatsoever with the former skill. PSM will prevent you from learning the latter skill. So long as you are always using PSM, you may not care. However, once you go from a PSM car to a non-PSM car, you need to realize that you may not have adequate experience with the lattter skill.
I hope this provides a more useful framework to discuss the problem.
I started track driving in a 996 with PSM. I never turned it off. I rarely had PSM activate. I had learned the former skill rather well, or perhaps I never really pushed close enough to the limit that it really mattered.
Then I bought a n/a 944 racecar that didn't even have PSM. Although I rarely spun, I was forced to learn the latter skill.
Now that I have a club coupe, I will leave PSM on if and when I take it to the track again. I have nothing to prove to anyone, and it definitely will not "slow me down"
10-08-2007, 07:08 PM
#26
Race Car
From your nick and your avatar, I'll assume you're talking about PSM in the 996. I've heard complaints about the system being overly aggressive in those cars so I'll agree there's a place to disabling the system.
This is a 997 forum though, and the system in these cars is quite different. It's much more compliant and hardly intrusive so long as you remain in control of the car. Sport Chrono allows the system to be relaxed further. PSM is just like time at the track: A tool to help people become better drivers. Like all tools, you haveto learn how it works and how to use it to use it well. Pay attention to when it activates and figure out why. If you can predict exactly when and why the system will intervene before you do something, then think about turning it off. Until then, well you get a lot more seat time if you don't wreck your ride.
I've heard a lot of people say they turn their stability control systems off because "they just slow me down". That vast majority of those guys ended up flatbedding their cars home after stuffing them into a wall. This isn't a hypothetical: Last summer at RA a guy bragged about how he turned the system off in his 350Z because it was only slowing him down and he totaled his car that afternoon. He wasn't hurt, but a little electronic help could have saved his car and his weekend. I've not seen him at the track since.
My experience has been that when I'm driving well, I never hear a peep from PSM on the street or at the track. I usually have to screw up pretty good to need its help, but then I'm glad I have it. I analyze my mistake, learn from it, and go for another lap.
This is a 997 forum though, and the system in these cars is quite different. It's much more compliant and hardly intrusive so long as you remain in control of the car. Sport Chrono allows the system to be relaxed further. PSM is just like time at the track: A tool to help people become better drivers. Like all tools, you haveto learn how it works and how to use it to use it well. Pay attention to when it activates and figure out why. If you can predict exactly when and why the system will intervene before you do something, then think about turning it off. Until then, well you get a lot more seat time if you don't wreck your ride.
I've heard a lot of people say they turn their stability control systems off because "they just slow me down". That vast majority of those guys ended up flatbedding their cars home after stuffing them into a wall. This isn't a hypothetical: Last summer at RA a guy bragged about how he turned the system off in his 350Z because it was only slowing him down and he totaled his car that afternoon. He wasn't hurt, but a little electronic help could have saved his car and his weekend. I've not seen him at the track since.
My experience has been that when I'm driving well, I never hear a peep from PSM on the street or at the track. I usually have to screw up pretty good to need its help, but then I'm glad I have it. I analyze my mistake, learn from it, and go for another lap.
My comment was not about whether it makes your car faster or slower, but that it is nothing more than a "sissy" control at a track. Put rails around the track and you can be even faster.
Great safety feature for the occasional tracker, but if you want to learn to drive your car to the limit and become a more solid driver.....remove PSM completely. Racing is about the driver's abiity and not the car's. Driver to YOUR limit and not the cars.
10-08-2007, 07:09 PM
#27
My comment was not about whether it makes your car faster or slower, but that it is nothing more than a "sissy" control at a track. Put rails around the track and you can be even faster. Great safety feature for the poor drivers, but if you want to learn to drive your car to the limit and become a more solid driver.....remove PSM completely. Racing is about the driver's abiity and not the car's.
Great safety feature for the poor drivers, but if you want to learn to drive your car to the limit and become a more solid driver.....remove PSM completely. Racing is about the driver's abiity and not the car's.
10-08-2007, 07:19 PM
#28
Race Car
10-08-2007, 07:21 PM
#29
10-08-2007, 07:22 PM
#30
Rennlist Member
One of the most startling discoveries for me with the 997 was how much more useful PSM is. If I'm driving smoothly I can leave it on and my times aren't really impacted at all. I turn it off when I autocross, largely so I have some chance to work on that second skill you mention, but doing so doesn't improve my times in any way. When I pull off a good, clean lap I won't have done anything to trigger the PSM. It's only when I screw up that the setting becomes a factor.