Can you feel PASM working dynamically?
09-14-2011, 01:02 PM
#1
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Thread Starter
Can you feel PASM working dynamically?
I'm not sure I ever have.
I understand that even in normal mode that the suspension adjusts dynamically (I.e if I accelerate suddenly or corner sharply). I'm not sure if I've ever noticed that. Psychologically, sport mode always 'feels' tighter and sharper than normal mode under some sort of high performance turn.
What about you guys?
I understand that even in normal mode that the suspension adjusts dynamically (I.e if I accelerate suddenly or corner sharply). I'm not sure if I've ever noticed that. Psychologically, sport mode always 'feels' tighter and sharper than normal mode under some sort of high performance turn.
What about you guys?
09-14-2011, 02:36 PM
#3
Me too.. very different, the ride is harsher and more like a track car. The car body leans slightly less readily going into corners. Are you asking as to whether it actively does something? remember, it's not like it's a pneumatic lift. The computer controls the damping. So, by nature the car has to be compressing (or pulling the weight off of) the spring caused by abberations in the terrain for you to feel anything.
09-14-2011, 02:55 PM
#4
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OP is not asking about the difference between 'normal' and 'sport' ranges of PASM, but rather whether you can feel PASM dynamically self-adjusting itself to road conditions and/or driving inputs WITHIN the selected range.
My answer (based on 20k miles in a PASM-equiped Cayman S), is no, I couldn't feel the dynamic changes except to say that, at the track there was occasionally a certain fuzzyness to the damping when conditions suddenly changed, for example when you initiate hard braking on a smooth surface and then the track subsequently becomes bumpy while you are still on the brakes... PASM perhaps was switching from one algorithm ("module" see below) to another. Hard to know for sure.
PASM knows 5 tricks (aka "modules"). That is all it knows. It is constantly trying to figure out which of these to use.
From the factory verbiage on PASM:
/begin quote/:
Operating principles of PASM
PASM selects the required damper hardness for each individual wheel from a precisely co-ordinated map in both the Normal and the Sport programme. The possible damper settings range from comfortable to decidedly sporty. Both programmes, which overlap slightly in some areas, are additionally superimposed with five special software modules to provide the optimum damper settings for every driving condition.
The system automatically selects the appropriate damper hardness based on the PASM programme selected and the driving condition identified.
The Normal programme offers comfortable settings with low damper forces. Special control algorithms in the PASM software modules enable the chassis to offer greater active driving safety in extreme driving situations, even with the Normal programme. To increase driving safety at higher speeds, the dampers are automatically switched to a harder damper setting as speed increases.
The dampers switch to a hard characteristic when Sport mode is activated. This offers superior agility and excellent steering precision on uneven surfaces. If the system detects an uneven driving surface in Sport mode, it immediately switches to a softer characteristic to improve contact with the road surface. PASM selects the optimum damper setting for this softer characteristic from the Sport map.
Since extremely hard damping is not always the ideal solution in every driving situation (depending on the driving surface, the vehicle may start to bounce or shift), the intentional overlap between the Normal and Sport maps allows a noticeably soft setting to be selected if necessary. The customer gets an “active sports chassis” which automatically responds to the actual road surface and switches from a hard, sporty damping setting to a comfortable range as necessary. PASM switches back to the original characteristic as soon as the road surface is smooth enough.
The following is a detailed description of the five software modules overlapping Normal and Sport mode.
Lane-change module
The damper forces at both axles are immediately increased in response to rapid steering movements, for example sudden evasive manoeuvres. This reduces body tilt and instability, thereby significantly improving vehicle control even in extreme situations.
Vertical-control module
In the Normal programme, the damper force is increased as soon as the vertical movement of the body, for example when driving over uneven surfaces, rises over a specific threshold value. This prevents body instability and therefore woolly driving behaviour.
In the Sport programme, the damping is slightly reduced automatically to improve contact between the road and the wheels as body movements increase. This also results in a noticeable increase in comfort.
Lateral-acceleration module
If specific, speed-dependent thresholds for lateral acceleration are exceeded when cornering in the Normal programme, the damper force is increased by different, defined amounts for each side of the vehicle. This prevents vehicle instability and significantly increases driving precision.
In the event of large vertical movements and high lateral acceleration coinciding, the higher of the vertical-control and lateral-acceleration damping values is set. This happens if, for example, the damping in the Sport programme was previously decreased by the vertical-control module.
Brake module
PASM switches to harder damping at the start of a braking operation to reduce vehicle nose-dive when braking. This way, higher brake forces can be transmitted to the road faster. It switches back to a softer setting (this setting is different for the front and rear axle) after a specific amount of time. The result is improved road contact, and thus a shorter braking distance, particularly when braking on uneven surfaces.
Load-change module
The damper characteristics for the front and rear axle are individually switched when accelerating heavily, releasing the throttle or changing lanes. In Normal mode, the dampers are briefly switched to a harder damping setting in these driving conditions. This avoids excessive lifting or diving at the front of the vehicle (“pitching”). In Sport mode, a softer damper characteristic is briefly selected if necessary to improve traction when accelerating, particularly on uneven surfaces.
Components
The PASM system comprises the following components:
• Four dampers with continuously adjustable damping force (each with one bypass valve)
• PASM control module
• Two acceleration sensors for detecting vertical movement of the body (one at the damper dome at the front right and one at the rear left). Further signals such as lateral acceleration, steering angle, travel speed, brake pressure, engine torque, etc. are read in via the CAN bus.
• One button for selecting the programme (Normal or Sport)
The system measures body movements via one acceleration sensor on each axle (front and rear). Values such as lateral acceleration, steering wheel angle, vehicle speed and information on possible braking operations are provided by the PSM via the CAN bus. Engine rpm and torque values are provided by the Motronic via the CAN bus.
/end quote/
My answer (based on 20k miles in a PASM-equiped Cayman S), is no, I couldn't feel the dynamic changes except to say that, at the track there was occasionally a certain fuzzyness to the damping when conditions suddenly changed, for example when you initiate hard braking on a smooth surface and then the track subsequently becomes bumpy while you are still on the brakes... PASM perhaps was switching from one algorithm ("module" see below) to another. Hard to know for sure.
PASM knows 5 tricks (aka "modules"). That is all it knows. It is constantly trying to figure out which of these to use.
From the factory verbiage on PASM:
/begin quote/:
Operating principles of PASM
PASM selects the required damper hardness for each individual wheel from a precisely co-ordinated map in both the Normal and the Sport programme. The possible damper settings range from comfortable to decidedly sporty. Both programmes, which overlap slightly in some areas, are additionally superimposed with five special software modules to provide the optimum damper settings for every driving condition.
The system automatically selects the appropriate damper hardness based on the PASM programme selected and the driving condition identified.
The Normal programme offers comfortable settings with low damper forces. Special control algorithms in the PASM software modules enable the chassis to offer greater active driving safety in extreme driving situations, even with the Normal programme. To increase driving safety at higher speeds, the dampers are automatically switched to a harder damper setting as speed increases.
The dampers switch to a hard characteristic when Sport mode is activated. This offers superior agility and excellent steering precision on uneven surfaces. If the system detects an uneven driving surface in Sport mode, it immediately switches to a softer characteristic to improve contact with the road surface. PASM selects the optimum damper setting for this softer characteristic from the Sport map.
Since extremely hard damping is not always the ideal solution in every driving situation (depending on the driving surface, the vehicle may start to bounce or shift), the intentional overlap between the Normal and Sport maps allows a noticeably soft setting to be selected if necessary. The customer gets an “active sports chassis” which automatically responds to the actual road surface and switches from a hard, sporty damping setting to a comfortable range as necessary. PASM switches back to the original characteristic as soon as the road surface is smooth enough.
The following is a detailed description of the five software modules overlapping Normal and Sport mode.
Lane-change module
The damper forces at both axles are immediately increased in response to rapid steering movements, for example sudden evasive manoeuvres. This reduces body tilt and instability, thereby significantly improving vehicle control even in extreme situations.
Vertical-control module
In the Normal programme, the damper force is increased as soon as the vertical movement of the body, for example when driving over uneven surfaces, rises over a specific threshold value. This prevents body instability and therefore woolly driving behaviour.
In the Sport programme, the damping is slightly reduced automatically to improve contact between the road and the wheels as body movements increase. This also results in a noticeable increase in comfort.
Lateral-acceleration module
If specific, speed-dependent thresholds for lateral acceleration are exceeded when cornering in the Normal programme, the damper force is increased by different, defined amounts for each side of the vehicle. This prevents vehicle instability and significantly increases driving precision.
In the event of large vertical movements and high lateral acceleration coinciding, the higher of the vertical-control and lateral-acceleration damping values is set. This happens if, for example, the damping in the Sport programme was previously decreased by the vertical-control module.
Brake module
PASM switches to harder damping at the start of a braking operation to reduce vehicle nose-dive when braking. This way, higher brake forces can be transmitted to the road faster. It switches back to a softer setting (this setting is different for the front and rear axle) after a specific amount of time. The result is improved road contact, and thus a shorter braking distance, particularly when braking on uneven surfaces.
Load-change module
The damper characteristics for the front and rear axle are individually switched when accelerating heavily, releasing the throttle or changing lanes. In Normal mode, the dampers are briefly switched to a harder damping setting in these driving conditions. This avoids excessive lifting or diving at the front of the vehicle (“pitching”). In Sport mode, a softer damper characteristic is briefly selected if necessary to improve traction when accelerating, particularly on uneven surfaces.
Components
The PASM system comprises the following components:
• Four dampers with continuously adjustable damping force (each with one bypass valve)
• PASM control module
• Two acceleration sensors for detecting vertical movement of the body (one at the damper dome at the front right and one at the rear left). Further signals such as lateral acceleration, steering angle, travel speed, brake pressure, engine torque, etc. are read in via the CAN bus.
• One button for selecting the programme (Normal or Sport)
The system measures body movements via one acceleration sensor on each axle (front and rear). Values such as lateral acceleration, steering wheel angle, vehicle speed and information on possible braking operations are provided by the PSM via the CAN bus. Engine rpm and torque values are provided by the Motronic via the CAN bus.
/end quote/
09-14-2011, 07:24 PM
#5
Rennlist Member
Thread Starter
Immensely helpful quickxotica, thanks.
09-14-2011, 08:02 PM
#6
Three Wheelin'
"Can you feel the PASM working dynamically?"
Yes and No.
Yes. In my previous car, 2008 C2S, I would feel it and the PSM when entering and exiting my driveway. If went too fast in or out the PSM would try to adjust and the PASM kicked in it seemed at the same time. Understand that I live on a hill (14% slope) and the driveway angles quickly to level as you pull in so simply by going about 7 or 8 mph was enough to set the systems off. I would also feel the PASM kick in on normal mode with spirited driving around the Bay Area - to call the roads undulating doesn't really do them justice. (And by spirited driving I don't mean 70 in a 20 zone around a blind curve - just stretching the cars legs a bit when it was safe.) I also felt it on the track once when I left it in normal mode to see how differently the car handled (yes, it handled differently - Duh)
No. I have never felt it under normal driving conditions in the 08. I really haven't driven the GTS hard enough yet to say that I've felt any difference but the PSM, SPASM does not kick in when I go in or out of my driveway.
Yes and No.
Yes. In my previous car, 2008 C2S, I would feel it and the PSM when entering and exiting my driveway. If went too fast in or out the PSM would try to adjust and the PASM kicked in it seemed at the same time. Understand that I live on a hill (14% slope) and the driveway angles quickly to level as you pull in so simply by going about 7 or 8 mph was enough to set the systems off. I would also feel the PASM kick in on normal mode with spirited driving around the Bay Area - to call the roads undulating doesn't really do them justice. (And by spirited driving I don't mean 70 in a 20 zone around a blind curve - just stretching the cars legs a bit when it was safe.) I also felt it on the track once when I left it in normal mode to see how differently the car handled (yes, it handled differently - Duh)
No. I have never felt it under normal driving conditions in the 08. I really haven't driven the GTS hard enough yet to say that I've felt any difference but the PSM, SPASM does not kick in when I go in or out of my driveway.
09-14-2011, 09:44 PM
#7
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PASM doesn't "kick in". That's PSM or something in the driveline you were feeling on your driveway. At any speed under 10mph, if you can feel the damping changes going on in your shocks, Bilstein would probably love to hire you as a test driver.
Not trying to be inflammatory, but way too many people conflate PSM and PASM when they act on completely different parts of the car.
Not trying to be inflammatory, but way too many people conflate PSM and PASM when they act on completely different parts of the car.
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09-15-2011, 12:38 AM
#8
Three Wheelin'
PASM doesn't "kick in". That's PSM or something in the driveline you were feeling on your driveway. At any speed under 10mph, if you can feel the damping changes going on in your shocks, Bilstein would probably love to hire you as a test driver.
Not trying to be inflammatory, but way too many people conflate PSM and PASM when they act on completely different parts of the car.
Not trying to be inflammatory, but way too many people conflate PSM and PASM when they act on completely different parts of the car.
