Threshold behavior with PSM, have you ever spun your 996tt?
11-04-2016, 08:45 PM
#31
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porsche had to incorporate psm ( and why wouldn't they!?.. as it has saved lives, I'm sure ) for the 996 turbos to accomodate the bankers and lawyers who first bought the cars. psm tamed them enough ( with the addition of psm ) to service this segment of the market. they arguably also became less "special" by the sheer numbers of the numbers of turbos built.
i can imagine that somewhere in their collective mindset in zuffenhausen they were not to soon forget that even guys like vasek polak were killing themselves in 993 turbo's.
my take on psm and it HAS saved me ( as i was learning the car..) is that it looks great on PAPER ( and actually is pretty cool stuff to have in a millisecond pinch )
but it sure sucks to have the brakes stabbed when you really DONT want them stabbed
some good info on "it" here:
PSM monitors the ABS sensors (which measure the speed of each wheel), engine speed (RPM), throttle position (via E-Gas), gear selection, lateral acceleration (side to side), yaw (the car spinning in a circle), and steering wheel position. This enables the PSM to detect oversteer and understeer. It basically determines the slip angle of the front and rear tires, or more simply, when the car is not going where the steering wheel is pointed. Oversteer is minimized by automatically applying the brake on the outer front wheel in a bend, slowing the rotation of the car; understeer is minimized by applying the brake on the inner rear wheel, speeding the car�s rotation. No driver will be able to do that until Porsche develops a car with four brake pedals. However, PSM is not only a braking system. If you lift off the throttle in a low traction situation (wet, snow, etc.) and the back of the car gets loose, PSM will increase the engine speed (blip the throttle) to keep the car in line. Also, if traction is low, PSM can use engine braking (EDC � engine drag torque control) to slow the car. PSM can calculate the amount of available traction by comparing wheel speeds at all four corners of the car.
Recognizing that even street drivers expect excitement from their Porsches, PSM allows approximately seven percent slip angle before intervening. Five to seven percent is generally agreed to be the limit for modern, high performance tires. The biggest difference between PSM and the other systems on the market today (Mercedes Benz, BMW, Jaguar, etc.) is that PSM is programmed to allow a good deal of slip, as you can see. All of these other systems clamp down the moment any slip (i.e., fun driving) is detected.
However, if you require more fun, you can turn the PSM off. When you "turn it off," you are taking only the outputs offline. The PSM system is still collecting data from the ABS system, the yaw sensor, the lateral acceleration sensors and the steering wheel position sensor. If you have PSM off, and the levels of slip are exceeded, and you do not touch the brakes, the car will continue to slide.
If you have not exceeded the levels of slip allowed, and apply the brakes (no matter how hard), PSM will not active its outputs. However, if you have exceeded the levels, AND apply the brakes (no matter how hard), PSM will activate until the car has regained control or you get off the brakes, at which point PSM stops outputting. PSM assumes that since you hit the brakes that you are not comfortable with the level of sliding and that you want it to help. This answers the question, posed by Mike Furnish on the PCASD forum, that inspired this article, "what happens in a spin when you put both feet in?" Presuming that you put in the correct two pedals, PSM will activate.
So what about PSM and racing? At this point in my career, PSM is an asset to my racing. It has allowed me to more confidently explore the limits of traction on the first few laps at a new track, particularly in scarier corners, e.g., Turn 8 at Willow Springs. I was very happy to have it at Phoenix International Raceway, a track with concrete barriers everywhere. When PSM activates you can feel it, much like you can feel ABS. It will show you where you are losing traction while keeping you on the track if the loss was unintentional. When it engages, it may slow you down where you might not want it to later, i.e., where you really do want more oversteer, but on those first few practice laps, who cares? You can actually throttle steer the car quite well with PSM on as long as you are smooth, the yaw is not excessive, and the corner is fast enough to allow smooth inputs. This in itself is a good training tool. So PSM is good for practice, but what about when it matters, during timed laps?
In a time trial situation, it would depend on the course whether it would matter if PSM were on or off. On a tight road course, you would most likely want it off. On an autocross track, you want it off for sure. If you had sufficient presence of mind on a road course you could turn it on and off depending on the corner. You could make sure it�s off for Turn 2 and 4 at Willow Springs, turns where throttle steering comes into play. You could turn it on for Turn 8, the last place on earth you want to see your tail catching up with you. I've never done this, but it illustrates the point.
So far, so good. Since you can turn PSM off, why wouldn�t you want to buy it, even for a car you intend to race? It seems like the best of both worlds. However, remember above where I said that when PSM is off, it is still collecting data and if you hit the brakes when the levels of slip are exceeded, it will intervene. That could be a negative in one racing technique, trail braking, where you are obviously on the brakes and turning. There are two reasons to trail brake, one in which PSM is neutral or even a positive, and one in which it can interfere with the driver�s intention. The first is when you are trail braking to lengthen the straight or to maintain a higher speed through the first part of a turn. In this case, you want the car to stay on its directed path. If things are going as intended, PSM is very unlikely to engage even though you are on the brakes. If it does, it is probably because you lost rear traction in a pretty big way. By engaging it didn�t cost you time since your intention was to slow down anyway and it may have saved you from spinning. The second use of trail braking serves a different purpose. If you are trail braking to induce some oversteer intentionally to tighten the corner, PSM could interfere in the same way as when it is on and you lift to oversteer. While I have a lot of experience throttle steering the car, with PSM on and off, I don�t brake to loosen the rear of my 996 C2. Lifting is normally sufficient. However, I have seen this technique, in the form of left-foot braking, used in a friend�s 993 C4 in Turn 4 at Willow and Turn 5b at Spring Mountain and presume it would be useful in the newer 996 C4. Since the 993 does not have PSM, I cannot tell you to what extent it would have interfered. If you are smooth, probably very little, if at all. But, this is one possible negative to weigh against the aforementioned positives. I think it�s worth it, but let me give the last word to Porsche.
"We wanted the car to perform like a Porsche not a family saloon, so the system has been designed for minimal intrusion," explained Thomas Herold, the Carrera 4 Project Manager. "Its limits are really high and you can reach the same lateral g-force number with the system in or out on a steady state cornering circle. Thus, if you are a good driver, you can keep the power on in a drift and even adjust the car�s attitude on power in a corner without interference. But if you lift off suddenly or brake, and the car is in danger of destabilizing, the system will reach out and save you."
"The difference is small around the Nurburgring for a skilled test driver," he explained. "Within one second a lap in fact. This is the way the car is made. If you are smooth, there is no interference from the system. But if you are ragged, the system will be cutting in all the time to stabilize the car, so an aggressive driver will be slower with the system on."[/B]
i can imagine that somewhere in their collective mindset in zuffenhausen they were not to soon forget that even guys like vasek polak were killing themselves in 993 turbo's.
my take on psm and it HAS saved me ( as i was learning the car..) is that it looks great on PAPER ( and actually is pretty cool stuff to have in a millisecond pinch )
but it sure sucks to have the brakes stabbed when you really DONT want them stabbed
some good info on "it" here:
PSM monitors the ABS sensors (which measure the speed of each wheel), engine speed (RPM), throttle position (via E-Gas), gear selection, lateral acceleration (side to side), yaw (the car spinning in a circle), and steering wheel position. This enables the PSM to detect oversteer and understeer. It basically determines the slip angle of the front and rear tires, or more simply, when the car is not going where the steering wheel is pointed. Oversteer is minimized by automatically applying the brake on the outer front wheel in a bend, slowing the rotation of the car; understeer is minimized by applying the brake on the inner rear wheel, speeding the car�s rotation. No driver will be able to do that until Porsche develops a car with four brake pedals. However, PSM is not only a braking system. If you lift off the throttle in a low traction situation (wet, snow, etc.) and the back of the car gets loose, PSM will increase the engine speed (blip the throttle) to keep the car in line. Also, if traction is low, PSM can use engine braking (EDC � engine drag torque control) to slow the car. PSM can calculate the amount of available traction by comparing wheel speeds at all four corners of the car.
Recognizing that even street drivers expect excitement from their Porsches, PSM allows approximately seven percent slip angle before intervening. Five to seven percent is generally agreed to be the limit for modern, high performance tires. The biggest difference between PSM and the other systems on the market today (Mercedes Benz, BMW, Jaguar, etc.) is that PSM is programmed to allow a good deal of slip, as you can see. All of these other systems clamp down the moment any slip (i.e., fun driving) is detected.
However, if you require more fun, you can turn the PSM off. When you "turn it off," you are taking only the outputs offline. The PSM system is still collecting data from the ABS system, the yaw sensor, the lateral acceleration sensors and the steering wheel position sensor. If you have PSM off, and the levels of slip are exceeded, and you do not touch the brakes, the car will continue to slide.
If you have not exceeded the levels of slip allowed, and apply the brakes (no matter how hard), PSM will not active its outputs. However, if you have exceeded the levels, AND apply the brakes (no matter how hard), PSM will activate until the car has regained control or you get off the brakes, at which point PSM stops outputting. PSM assumes that since you hit the brakes that you are not comfortable with the level of sliding and that you want it to help. This answers the question, posed by Mike Furnish on the PCASD forum, that inspired this article, "what happens in a spin when you put both feet in?" Presuming that you put in the correct two pedals, PSM will activate.
So what about PSM and racing? At this point in my career, PSM is an asset to my racing. It has allowed me to more confidently explore the limits of traction on the first few laps at a new track, particularly in scarier corners, e.g., Turn 8 at Willow Springs. I was very happy to have it at Phoenix International Raceway, a track with concrete barriers everywhere. When PSM activates you can feel it, much like you can feel ABS. It will show you where you are losing traction while keeping you on the track if the loss was unintentional. When it engages, it may slow you down where you might not want it to later, i.e., where you really do want more oversteer, but on those first few practice laps, who cares? You can actually throttle steer the car quite well with PSM on as long as you are smooth, the yaw is not excessive, and the corner is fast enough to allow smooth inputs. This in itself is a good training tool. So PSM is good for practice, but what about when it matters, during timed laps?
In a time trial situation, it would depend on the course whether it would matter if PSM were on or off. On a tight road course, you would most likely want it off. On an autocross track, you want it off for sure. If you had sufficient presence of mind on a road course you could turn it on and off depending on the corner. You could make sure it�s off for Turn 2 and 4 at Willow Springs, turns where throttle steering comes into play. You could turn it on for Turn 8, the last place on earth you want to see your tail catching up with you. I've never done this, but it illustrates the point.
So far, so good. Since you can turn PSM off, why wouldn�t you want to buy it, even for a car you intend to race? It seems like the best of both worlds. However, remember above where I said that when PSM is off, it is still collecting data and if you hit the brakes when the levels of slip are exceeded, it will intervene. That could be a negative in one racing technique, trail braking, where you are obviously on the brakes and turning. There are two reasons to trail brake, one in which PSM is neutral or even a positive, and one in which it can interfere with the driver�s intention. The first is when you are trail braking to lengthen the straight or to maintain a higher speed through the first part of a turn. In this case, you want the car to stay on its directed path. If things are going as intended, PSM is very unlikely to engage even though you are on the brakes. If it does, it is probably because you lost rear traction in a pretty big way. By engaging it didn�t cost you time since your intention was to slow down anyway and it may have saved you from spinning. The second use of trail braking serves a different purpose. If you are trail braking to induce some oversteer intentionally to tighten the corner, PSM could interfere in the same way as when it is on and you lift to oversteer. While I have a lot of experience throttle steering the car, with PSM on and off, I don�t brake to loosen the rear of my 996 C2. Lifting is normally sufficient. However, I have seen this technique, in the form of left-foot braking, used in a friend�s 993 C4 in Turn 4 at Willow and Turn 5b at Spring Mountain and presume it would be useful in the newer 996 C4. Since the 993 does not have PSM, I cannot tell you to what extent it would have interfered. If you are smooth, probably very little, if at all. But, this is one possible negative to weigh against the aforementioned positives. I think it�s worth it, but let me give the last word to Porsche.
"We wanted the car to perform like a Porsche not a family saloon, so the system has been designed for minimal intrusion," explained Thomas Herold, the Carrera 4 Project Manager. "Its limits are really high and you can reach the same lateral g-force number with the system in or out on a steady state cornering circle. Thus, if you are a good driver, you can keep the power on in a drift and even adjust the car�s attitude on power in a corner without interference. But if you lift off suddenly or brake, and the car is in danger of destabilizing, the system will reach out and save you."
"The difference is small around the Nurburgring for a skilled test driver," he explained. "Within one second a lap in fact. This is the way the car is made. If you are smooth, there is no interference from the system. But if you are ragged, the system will be cutting in all the time to stabilize the car, so an aggressive driver will be slower with the system on."[/B]
11-06-2016, 06:54 PM
#33
PSM
porsche had to incorporate psm ( and why wouldn't they!?.. as it has saved lives, I'm sure ) for the 996 turbos to accomodate the bankers and lawyers who first bought the cars. psm tamed them enough ( with the addition of psm ) to service this segment of the market. they arguably also became less "special" by the sheer numbers of the numbers of turbos built.
i can imagine that somewhere in their collective mindset in zuffenhausen they were not to soon forget that even guys like vasek polak were killing themselves in 993 turbo's.
i can imagine that somewhere in their collective mindset in zuffenhausen they were not to soon forget that even guys like vasek polak were killing themselves in 993 turbo's.
my take on psm and it HAS saved me ( as i was learning the car..) is that it looks great on PAPER ( and actually is pretty cool stuff to have in a millisecond pinch )
but it sure sucks to have the brakes stabbed when you really DONT want them stabbed
...
If you are trail braking to induce some oversteer intentionally to tighten the corner, PSM could interfere in the same way as when it is on and you lift to oversteer.
...
"The difference is small around the Nurburgring for a skilled test driver," he explained. "Within one second a lap in fact. This is the way the car is made. If you are smooth, there is no interference from the system. But if you are ragged, the system will be cutting in all the time to stabilize the car, so an aggressive driver will be slower with the system on."
but it sure sucks to have the brakes stabbed when you really DONT want them stabbed
...
If you are trail braking to induce some oversteer intentionally to tighten the corner, PSM could interfere in the same way as when it is on and you lift to oversteer.
...
"The difference is small around the Nurburgring for a skilled test driver," he explained. "Within one second a lap in fact. This is the way the car is made. If you are smooth, there is no interference from the system. But if you are ragged, the system will be cutting in all the time to stabilize the car, so an aggressive driver will be slower with the system on."
For the record, I think it's great that the 996T came with PSM standard. I just wish that - in addition to the pseudo-off that Porsche provides - pressing the off button for, say, more than 3 seconds would completely, utterly and totally turn it off. OK, unplugging under the brake fluid reservoir achieves the same thing, but it is not a particularly elegant way to go about it.
I am still interested to hear more about the car's dynamics in a spin with PSM on though. Once through say, 270 degrees, does it work to help straighten the car out again? And does it partially do it by severely limiting the available brake force?
Last edited by 996tnz; 11-06-2016 at 08:59 PM. Reason: Rennlist not picking up on quotes...
11-06-2016, 08:20 PM
#34
RL Community Team
Rennlist Member
Rennlist Member
I often drive on track with PSM fully on because for some reason it works well with my driving style.
I have heard others complain that PSM cuts all power and ruins their driving. PSM kicks in on me all the time and I never lose power. As friend of mine once said after taking a ride with me, I don't drive with the PSM, I drive on it. Meaning I use as a speed aid. I use it to go faster. Rather than slowing me down the PSM will settle any unbalance in my cornering drift and allow me power my way out with good pace.
Occasionally I will over do it. Mostly on hill crest corners and decreasing radius corners. I get on the power too hard or go in too hot. Try to guide the car to the apex and the car says no. Sometime the front washes out or back end steps out. When the back steps out the car rotates about 180 degrees and just as I am counter steering and about to apply the brakes or throttle, which ever is best for the given situtation, the PSM kicks in and fixes the situation for me. Most times on lesser spins the PSM does such a good job of correction I am pointed in the right direction before I even know what happened. Often so quickly the folks behind gain almost no ground on me. I never lose control of the brakes or throttle. The PSM just corrects the unbalanced drift.
I am bit of an on/off throttle type of guy but very slow and deliberate with the steering and brakes so maybe that smooth gas hog style is why PSM works for/with me.
Last edited by Carlo_Carrera; 11-06-2016 at 09:26 PM.
11-06-2016, 08:59 PM
#35
I will confess some of my transgressions.
I often drive on track with PSM fully on because for some reason it works well with my driving style.
I have heard others complain that PSM cuts all power and ruins their driving. PSM kicks in on me all the time and I never lose power. As friend of mine once said after taking a ride with me, I don't drive with the PSM, I drive on it. Meaning I use as a speed aid. I use it to go faster. Rather than slowing me down the PSM will settle any unbalance in my cornering drift and allow me power my way out with good pace.
Occasionally I will over do it. Mostly on hill crest corners and decreasing radius corners. I get on the power too hard or go in too hot. Try to guide the car to the apex and the car says no. Sometime the front washes out or back end steps out. When the back steps out the car rotates about 180 degrees and just as I am counter steering and about to apply the brakes or throttle, which ever is best for the given situtation, the PSM kicks in and fixes the situation for me. Often so quickly the folks behind gain almost no ground on me. Sometime the PSM does such a good job of correction I am pointed in the right direction before I even know what happened. I never lose control of the brakes or throttle. The PSM just corrects the unbalanced drift.
I am bit of an on/off throttle type of guy so maybe that gas hog style is why PSM work for me.
I often drive on track with PSM fully on because for some reason it works well with my driving style.
I have heard others complain that PSM cuts all power and ruins their driving. PSM kicks in on me all the time and I never lose power. As friend of mine once said after taking a ride with me, I don't drive with the PSM, I drive on it. Meaning I use as a speed aid. I use it to go faster. Rather than slowing me down the PSM will settle any unbalance in my cornering drift and allow me power my way out with good pace.
Occasionally I will over do it. Mostly on hill crest corners and decreasing radius corners. I get on the power too hard or go in too hot. Try to guide the car to the apex and the car says no. Sometime the front washes out or back end steps out. When the back steps out the car rotates about 180 degrees and just as I am counter steering and about to apply the brakes or throttle, which ever is best for the given situtation, the PSM kicks in and fixes the situation for me. Often so quickly the folks behind gain almost no ground on me. Sometime the PSM does such a good job of correction I am pointed in the right direction before I even know what happened. I never lose control of the brakes or throttle. The PSM just corrects the unbalanced drift.
I am bit of an on/off throttle type of guy so maybe that gas hog style is why PSM work for me.
As pointed out by 02996ttx50, there are some cool things that PSM does, like braking individual wheels to help cornering (basically an e-diff), albeit at the expense of putting a lot more heat and wear into the brakes if going 10/10ths. It would be perfect if the system was user configurable and a la carte.
In that case I'd probably leave the e-diff on for sprints but perhaps not for enduros (or at least up its cut in point to save the rear brakes), and in all cases I'd:
- disable the throttle kill on braking (so the car can be properly balanced with both feet)
- disable the engine power cut feature
- reduce the soft close on lifting off the gas
- tweak the allowable drift angle higher
- tweak the e-proportioning to shift more braking to the back wheels.
But that's not possible so between on, pseudo-off, and disabled, I tend to prefer disabled.
On the related ABS front, I'd like to:
- increase the ABS trigger points for track use and track tires, ie have it recognise a 1.2 to 1.4g deceleration as allowable rather than start intervening at 1G.
- totally, utterly and permanently disable the 'ice mode' that cuts max braking power to about 30%, or at least reprogram the unit so the cut in point was twice as high and really could only engage on proper ice rather than on a race track.
I don't disable my ABS on purpose, but nor do I worry if it disables itself by failing to off while out on track, as it often does.
Of all the above, that ice mode is the biggest worry. Does anyone know for sure whether it is part of PSM or of ABS? I seem to remember it being a core part of the Bosch 5.7 ABS system rather than of PSM?
11-06-2016, 09:24 PM
#36
RL Community Team
Rennlist Member
Rennlist Member
Thanks Carlo for explaining. Best response yet to the OP's question. I take it though that you mean the car rotates 90 degrees and PSM saves you, or are you really travelling backwards? I am pretty impressed that it can pull itself back from 90 as that is the point where I'm shifting her into neutral and hitting the brakes as she comes around.
As pointed out by 02996ttx50, there are some cool things that PSM does, like braking individual wheels to help cornering (basically an e-diff), albeit at the expense of putting a lot more heat and wear into the brakes if going 10/10ths. It would be perfect if the system was user configurable and a la carte.
In that case I'd probably leave the e-diff on for sprints but perhaps not for enduros (or at least up its cut in point to save the rear brakes), and in all cases I'd:
- disable the throttle kill on braking (so the car can be properly balanced with both feet)
- disable the engine power cut feature
- reduce the soft close on lifting off the gas
- tweak the allowable drift angle higher
- tweak the e-proportioning to shift more braking to the back wheels.
But that's not possible so between on, pseudo-off, and disabled, I tend to prefer disabled.
On the related ABS front, I'd like to:
- increase the ABS trigger points for track use and track tires, ie have it recognise a 1.2 to 1.4g deceleration as allowable rather than start intervening at 1G.
- totally, utterly and permanently disable the 'ice mode' that cuts max braking power to about 30%, or at least reprogram the unit so the cut in point was twice as high and really could only engage on proper ice rather than on a race track.
I don't disable my ABS on purpose, but nor do I worry if it disables itself by failing to off while out on track, as it often does.
Of all the above, that ice mode is the biggest worry. Does anyone know for sure whether it is part of PSM or of ABS? I seem to remember it being a core part of the Bosch 5.7 ABS system rather than of PSM?
As pointed out by 02996ttx50, there are some cool things that PSM does, like braking individual wheels to help cornering (basically an e-diff), albeit at the expense of putting a lot more heat and wear into the brakes if going 10/10ths. It would be perfect if the system was user configurable and a la carte.
In that case I'd probably leave the e-diff on for sprints but perhaps not for enduros (or at least up its cut in point to save the rear brakes), and in all cases I'd:
- disable the throttle kill on braking (so the car can be properly balanced with both feet)
- disable the engine power cut feature
- reduce the soft close on lifting off the gas
- tweak the allowable drift angle higher
- tweak the e-proportioning to shift more braking to the back wheels.
But that's not possible so between on, pseudo-off, and disabled, I tend to prefer disabled.
On the related ABS front, I'd like to:
- increase the ABS trigger points for track use and track tires, ie have it recognise a 1.2 to 1.4g deceleration as allowable rather than start intervening at 1G.
- totally, utterly and permanently disable the 'ice mode' that cuts max braking power to about 30%, or at least reprogram the unit so the cut in point was twice as high and really could only engage on proper ice rather than on a race track.
I don't disable my ABS on purpose, but nor do I worry if it disables itself by failing to off while out on track, as it often does.
Of all the above, that ice mode is the biggest worry. Does anyone know for sure whether it is part of PSM or of ABS? I seem to remember it being a core part of the Bosch 5.7 ABS system rather than of PSM?
Ice mode is a fault in the ABS system. When it has happened to me it has always been cause by hitting a significant and abrupt bump while threshold braking.
Last edited by Carlo_Carrera; 11-06-2016 at 10:13 PM.
11-06-2016, 10:05 PM
#37
Yes, you are correct. Sorry I wasn't clearer. I edited my post ti be clearer. When I manage to do a 180 the PSM stops me dead. A 90 degree slide/drift is PSM corrected and straightened out quickly allowing me to basically keep driving.
Ice mode is a fault in the ABS system. When it has happened to me it has always been cause by hitting a significant and abrupt bump while threshold braking.
Ice mode is a fault in the ABS system. When it has happened to me it has always been cause by hitting a significant and abrupt bump while threshold braking.
Thanks too for the ice mode notes. I am yet to experience the dreaded ice mode (lift and reapply brakes seems to be the answer but sometimes there just isn't enough track for that), but that makes sense as I understand the main trigger for it is when a wheel slows improbably fast for the amount of brake pressure applied and the Gs on the car (as it would when locking up easily on ice). So super grabby race brakes, slicks or sticky R-comps, a high grip racing surface, bumps that lighten the front end (thanks for pointing those out) and especially various combinations of those all seem to increase the risk. Hopefully someone at Bosch or Porsche has been fired for the way ice mode was miscalibrated. Sure it's a road ABS system, but Porsche knows their customers are more likely than most to track their cars too.
11-07-2016, 08:39 AM
#38
i learned very early on in my (misspent) adolescence that "no" meant ( though possibly, maybe, "yes" at some point, but just not now! ).. "no".
but really! why shouldn't "off" mean "OFF"!
i also haven't taken advantage of the ease of mechanically disconnecting the system; just for knowing its got my back, for the two days a year it ( maybe? ) rains here in la.
Last edited by "02996ttx50; 11-07-2016 at 08:58 AM.
11-07-2016, 02:52 PM
#40
Three Wheelin'
That being said, even during my spirited canyon runs I leave the PSM on and rarely feel it intruding.
11-07-2016, 06:07 PM
#41
Thanks for the update. Interesting to find out more about PSM at (or a bit beyond) the limit.
Thanks too for the ice mode notes. I am yet to experience the dreaded ice mode (lift and reapply brakes seems to be the answer but sometimes there just isn't enough track for that), but that makes sense as I understand the main trigger for it is when a wheel slows improbably fast for the amount of brake pressure applied and the Gs on the car (as it would when locking up easily on ice). So super grabby race brakes, slicks or sticky R-comps, a high grip racing surface, bumps that lighten the front end (thanks for pointing those out) and especially various combinations of those all seem to increase the risk. Hopefully someone at Bosch or Porsche has been fired for the way ice mode was miscalibrated. Sure it's a road ABS system, but Porsche knows their customers are more likely than most to track their cars too.
Thanks too for the ice mode notes. I am yet to experience the dreaded ice mode (lift and reapply brakes seems to be the answer but sometimes there just isn't enough track for that), but that makes sense as I understand the main trigger for it is when a wheel slows improbably fast for the amount of brake pressure applied and the Gs on the car (as it would when locking up easily on ice). So super grabby race brakes, slicks or sticky R-comps, a high grip racing surface, bumps that lighten the front end (thanks for pointing those out) and especially various combinations of those all seem to increase the risk. Hopefully someone at Bosch or Porsche has been fired for the way ice mode was miscalibrated. Sure it's a road ABS system, but Porsche knows their customers are more likely than most to track their cars too.
11-07-2016, 10:00 PM
#42