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Discussion Starter #1
My car does not have sport chrono and my two traction control modes are either full on or full off. Does anyone know if PSM sport can be added via a software update?
 

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Psm sport includes active motor mounts
It should not surprise me if Porsche have taken that in account when they designed how it should work
 

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Discussion Starter #4
I thought it was more akin to “M dynamic mode” to throw a BMW reference out there. On bmw M cars there are 3 traction control settings: 1. Fully on 2. M dynamic (allows some wheel slip and higher higher threshold before interference) and 3. Fully off (better be careful)

Greg - why do you say full off isn’t possible?
 

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I've read that "fully off" only leaves ABS in operation.
 

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Yeah unless you mean ABS, PSM off definitely disables traction and stability control. I've had the car on skidpad multiple times and there's definitely no intervention with everything off.
 

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I thought it was more akin to “M dynamic mode” to throw a BMW reference out there. On bmw M cars there are 3 traction control settings: 1. Fully on 2. M dynamic (allows some wheel slip and higher higher threshold before interference) and 3. Fully off (better be careful)

Greg - why do you say full off isn’t possible?
That's what I read in the manual.
It's entirely possible that ABS is the only part left active.
I just leave it on all the time. I've seen way too many videos of "off" crashes to want to participate in one.
 

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Discussion Starter #8
Is ABS function connected to traction/stability control setting? I have never heard of the ability to change ABS function on a car, only traction control.

And yes I agree with you about turning traction control off completely as that level of car control is certainly above my skill level. That’s why I was asking about PSM sport as an in between setting to let you have a little fun but still save you if you push slightly too hard.
 

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Is ABS function connected to traction/stability control setting? I have never heard of the ability to change ABS function on a car, only traction control.

And yes I agree with you about turning traction control off completely as that level of car control is certainly above my skill level. That’s why I was asking about PSM sport as an in between setting to let you have a little fun but still save you if you push slightly too hard.
Yes, this is something I'm planning on testing out myself at my next HPDE. Here is a Porsche document that explains the feature better.
 

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Discussion Starter #10
Yes, this is something I'm planning on testing out myself at my next HPDE. Here is a Porsche document that explains the feature better.
Interesting. The way I am interpreting this is that ABS and PSM are not really connected (as expected). However, if you are in psm sport or psm off and you are hitting the brakes so hard as to activate the ABS, then psm will automatically intervene to attempt to get the vehicle back in control (even if psm was switched off).
 

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Interesting. The way I am interpreting this is that ABS and PSM are not really connected (as expected). However, if you are in psm sport or psm off and you are hitting the brakes so hard as to activate the ABS, then psm will automatically intervene to attempt to get the vehicle back in control (even if psm was switched off).
I think you are correct, but I think it is more interactive than that. Forgive me if you have seen this already, but before my first HPDE, during the required pre-event inspection, I was talking to the mechanic who was doing the inspection. I asked if I should turn PSM off and he said it didn't matter because the car recognizes you are driving aggresively in the track environment and will automatically adjust the PSM. I thought he was exaggerating (a nice way of saying "full of it") but that weekend they had professional Porsche drivers giving thrill rides and I picked the one who was driving a 718 Cayman S. It was a tail-out, crazy exciting thrill ride, including a long wide 180 degree curve and half way around we went sideways until we were lined up with the next straight and then boom, we were off down that straight like a rocket. I looked down at the center console and PSM was on. He confirmed it. I naturally assumed that what works one way, works the other which this document confirms, as you note. The point in the document that interests me, and makes me want to try Sport PSM next time on the track, is the bit that says, "Controllability at the performance limit is greatly improved by damping the vehicle's yawing behaviour". Again, I assume it does that automatically also, but WTH?
 
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Discussion Starter #12 (Edited)
I think you are correct, but I think it is more interactive than that. Forgive me if you have seen this already, but before my first HPDE, during the required pre-event inspection, I was talking to the mechanic who was doing the inspection. I asked if I should turn PSM off and he said it didn't matter because the car recognizes you are driving aggresively in the track environment and will automatically adjust the PSM. I thought he was exaggerating (a nice way of saying "full of it") but that weekend they had professional Porsche drivers giving thrill rides and I picked the one who was driving a 718 Cayman S. It was a tail-out, crazy exciting thrill ride, including a long wide 180 degree curve and half way around we went sideways until we were lined up with the next straight and then boom, we were off down that straight like a rocket. I looked down at the center console and PSM was on. He confirmed it. I naturally assumed that what works one way, works the other which this document confirms, as you note. The point in the document that interests me, and makes me want to try Sport PSM next time on the track, is the bit that says, "Controllability at the performance limit is greatly improved by damping the vehicle's yawing behaviour". Again, I assume it does that automatically also, but WTH?
Not doubting your experience at all but that sounds very strange to me that the vehicle would let the rear end slide aggressively with psm fully on. That actually sounds like a major safety concern. I have not tried this yet (plus I have a lowly base model with insufficient power to easily make the rear end step out) but I would fully expect traction control to intervene when it detects serious wheel slippage (hence the need for psm sport/psm off modes for track driving).
 

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This is getting quite complex—and fun. 😀
If the car/rear is sliding sideways but the wheels aren't turning significantly more or less than required by the speed, how does the PSM know? What info is it reading?
 

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Well, that's yaw, isn't it? And cars have yaw sensors, though I don't know how they work.

I think there is a tendency for some to over estimate the artificial intelligence capabilities of our cars. And I cannot believe that the car would be designed to dial back PSM control, without informing the driver, just when we need it.

I think the anecdote described is consistent with full PSM in operation - I think this is covered by Occam's razor. Did the driver have the throttle floored half way around? At the Corvette school, people are taught to pin the throttle at the apex - because stability management keeps them from looping it.

There are still limits of adhesion, and limits of PSM to stabilize the car. Otherwise, we could just get on a track and floor the throttle, and point with the steering. Then there are corners taken significantly slower than the limits of adhesion, where we would say that PSM is not intervening. And then there is the intersection of those two scenarios - where PSM is operating vigorously, but the car does not leave the track.

That's what the anecdote described sounds like to me: "Controllability at the performance limit is greatly improved by damping the vehicle's yawing behaviour".
 

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In fact, on the slide entitled "New “PSM Sport” mode: control strategy", it states "For safety reasons, the “PSM Sport” mode gets closer to the full system (PSM on) as the speed increases".

Under hard driving, full PSM does not selectively turn down; Sport PSM turns up.
 

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Not doubting your experience at all but that sounds very strange to me that the vehicle would let the rear end slide aggressively with psm fully on. That actually sounds like a major safety concern. I have not tried this yet (plus I have a lowly base model with insufficient power to easily make the rear end step out) but I would fully expect traction control to intervene when it detects serious wheel slippage (hence the need for psm sport/psm off modes for track driving).
I don't completely agree with the above in bold.
Yes, you can force an aggressive slide (physics) but if we're talking about how the car behaves while approaching traction limits it does intervene but VERY smoothly allowing some side slip.

Coming from the BMW world you will find a vast difference in how nanny controls are implemented with Porsche.
To me PSM fully on feels a little more like M dynamic mode but better.
It allows some slip without aggressive intervention and intervention is so smooth its almost transparent in comparison to BMW M cars.
You don't get the drastic throttle intervention like you do on M cars.

Nanny intervention dynamics is one of the things I appreciated the most coming from my Z4MC and E92M3.
Porsche does it brilliantly, and I still feel very safe in the car.
 

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This is getting quite complex—and fun. 😀
If the car/rear is sliding sideways but the wheels aren't turning significantly more or less than required by the speed, how does the PSM know? What info is it reading?
In track precision app there graphs both for front and rear slip.
How it work, no idea....
But with enough sensors it should not be thar hard i guess
 

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It knows the road speed; it knows how far the steering wheel is turned (i.e., where the front wheels are pointed). I would guess that those conditions would be enough to determine what the rotational speed of each rear wheel should be, if there was no loss of traction (no oversteer; no understeer). Thus, when it detects differences in rotational speed between the rear wheels that exceed that limit, it knows the car is oversteering or understeering.

Or does it know the road speed? Where does it get that info from? And how is road speed defined?

Or - perhaps more to the point - is it even necessary for yaw determination? If the car is going through a corner, at equilibrium, no loss of traction - does it matter how fast it's going to determine where the front wheels should be pointed, and the proper rotational speed of each rear wheel?

I'm really grasping here. Guys with degrees in automotive engineering know how this works.
 

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Discussion Starter #19
I don't completely agree with the above in bold.
Yes, you can force an aggressive slide (physics) but if we're talking about how the car behaves while approaching traction limits it does intervene but VERY smoothly allowing some side slip.

Coming from the BMW world you will find a vast difference in how nanny controls are implemented with Porsche.
To me PSM fully on feels a little more like M dynamic mode but better.
It allows some slip without aggressive intervention and intervention is so smooth its almost transparent in comparison to BMW M cars.
You don't get the drastic throttle intervention like you do on M cars.

Nanny intervention dynamics is one of the things I appreciated the most coming from my Z4MC and E92M3.
Porsche does it brilliantly, and I still feel very safe in the car.
Thanks for your insight and BMW comparison. I am most definitely used to BMWs as that is all I have been driving for last 10+ years until my 718. As you mentioned, the BMW traction control (especially in the F8x) can be very limiting and abrupt in it intervening. I assumed Porsche may be similar but it sounds like they give some more leeway to the driver.
 

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I've done some work on stability control systems in the aftermarket on Subarus.

On the Subaru you have a few sensors other than the obvious (road speed etc.). Some of the useful sensors are Steering wheel angle, Lateral acceleration and Yaw (rotational velocity in degree per second of the car in horizontal plane). In a grip situation without any under or oversteer happening you can use these sensors to cross reference each other. For instance if you have lateral G and road speed you can calculate the yaw rate and the steering wheel angle.... or vice versa. Under different non-grip situations, these sensors will no longer match and you can calculate slip angles based on the differences. For instance in an oversteer situation, the yaw rate will go initially go higher than expected for the lateral acceleration and roadspeed. Also the drivers response can be analyzed with steering angle and throttle (in oversteer the driver is likely to go for opposite lock).

If you know slip angles, you can make decisions on how much slip is allowed and when that limit is reached you can calculate how much preventative action you can take to arrest it. In the case of Subarus, this information was used to determine how much to lock the centre diff and in extreme slip angles how much to apply brakes to wheels.

Not sure if that helps?
 
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