How does PASM actually work

[le_gazman]

I’ve had my 991 Carrera S for a while now and think it’s actually more comfortable with PASM in Sport mode, but can’t really pinpoint why. It seems to stop it rebounding so much, so feels a bit tighter but that’s about it. It just feels better but not sure why.

[Twinfan]

It's all to do with damping rates. Valves are closed or opened electronically based on sensor settings around the car.

[ellroy]

If memory serves it isn’t an on/off system either. In normal mode it operates within a certain window, moving up to sport changes that range, so if you’re pressing on in normal you’re still in the bottom/mid of sport range as it were.

They did explain it at the PEC, but that’s a little while back.

[Adam B]

Correct

And (997) normal could give more comfort than a non-PASM car

I found Sport horrible on the rubbish UK roads (997 turbo)

[TDT]

Adam B said:

I found Sport horrible on the rubbish UK roads (997 turbo)

A DSC controller will fix that for you.

[jakesmith]

The dampers have a liquid in them like the normal oil but it has metal pieces in too that makes it magnetic
The damper has the capability to activate an electromagnetic field with variable strength around this liquid thus increasing or decreasing the stiffness of the damper
As commented above on the 997 (IDK for other cars) the system was always 'on' and it would adapt the suspension stiffness depending on sensor information and the car's perception of your driving style (sporty <----> comfort) presumably looking at things like how far you're reving it up the range and how much throttle you're using etc but also apparantly road conditions too
If you put the PASM mode into 'sport' it tightens it up to the most hard setting which is affectionately nicknames 'SPASM' as it is uncomfortable but serves 2 purposes (to me), firstly for track driving, and secondly when you're really 'on it' as combined with the PSE, and moving the shoulder and leg bolsters in on the adaptive seats, it created the perception of driving a more extreme car, like putting it into Exige mode kind of
Some people on here say it is essential if you have 19" wheels but I have had cars with and without it and didn't really think it made much difference.

[Twinfan]

The 9x7 version is well known for being way too hard in Sport. From 9x1 onwards it's usable in either setting and pretty darn good.

Both are always on, just in either Normal or Sport mode.

[isaldiri]

jakesmith said:

The dampers have a liquid in them like the normal oil but it has metal pieces in too that makes it magnetic
The damper has the capability to activate an electromagnetic field with variable strength around this liquid thus increasing or decreasing the stiffness of the damper

I don't believe that to be the case. The dampers described above are the GM magride system as used in the Corvette/R8/458/488 etc.

The PASM unit works by way of a control unit that changes the damping rate by the conventional damper system of allowing more oil through as required to provide extra damping force (ie more clicks per an adjustable system but done so via an added ecu that calculates various inputs. Iirc the early pasm system locks out 'normal' and 'sport' on opposite ends of the possible damping adjustments but on the later cars like the 991s, the allowed range seems much greater across both modes (so effectively similar to what the DSC module TDT mentioned does).

[David W.]

TDT said:

A DSC controller will fix that for you.

I got one for mine, it certainly does make the turbo more compliant in std setting, recommended.

Edited by David W. on Saturday 16th November 22:28

[jakesmith]

isaldiri said:

I don't believe that to be the case. The dampers described above are the GM magride system as used in the Corvette/R8/458/488 etc.

Whoops! In fairness I did replace my 997 with an R8. I'll get me coat....

[kilarney]

le_gazman said:

I’ve had my 991 Carrera S for a while now and think it’s actually more comfortable with PASM in Sport mode, but can’t really pinpoint why. It seems to stop it rebounding so much, so feels a bit tighter but that’s about it. It just feels better but not sure why.

It feels better because in your case the damping bump and rebound is matched to the spring rate correctly when in sport. Thing is the spring rate is fixed so technically there is only one damping rate that is correct for the spring rate. In short when you have it in soft its underdamped much like a knackered shock so thats what your feeling.

The damper works by having two orifice one fixed and one variable that the oil flows through, the variable one is gradually opened by an applied current up to 2000ma at which point its fully open and soft.
I played with the DSC controller on my PASM and concluded that the problem with pasm dampers is they suffer from cavitation (making them go soft )which increases with oil temperature and cycles hence why I really favour passive dampers. I set my DSC to three levels merely to counteract the temperature / cavitation issue but to maintain the same damping.

[le_gazman]

That’s really interesting, thanks. It does feel artificial and frankly loose or even knackered in Normal. It doesn’t feel properly connected till you go to sport.

Not sure what Sport Plus chassis does beyond Sport - just harder damping still?

[jakesmith]

le_gazman said:

That’s really interesting, thanks. It does feel artificial and frankly loose or even knackered in Normal. It doesn’t feel properly connected till you go to sport.

Not sure what Sport Plus chassis does beyond Sport - just harder damping still?

I'd be interested in this - sport mode does different things on different 911s.... from memory...

On my 997 it sharpens throttle response, allows more slip before kicking in PSM and turns on PSE

In the 997 Turbo sport mode gave you something like 20 seconds of overboost probably enough to get you close to 200 MPH, so without that you couldn't get the full power of the engine. Remap cheaper & can use the power all the time

In other cars sport plus does things like holds gears even longer into redline on PDK and maybe gives an even more aggressive throttle map. I seem to remember from the 997.2 onwards Sport Plus was only really worth it with PDK

[Adam B]

jakesmith said:

In the 997 Turbo sport mode gave you something like 20 seconds of overboost probably enough to get you close to 200 MPH, so without that you couldn't get the full power of the engine.

997 turbo

It gives you the overboost if you added sports chrono (50 more torque) which any sane person would, switches PSM to Sport (which I immediately switched back to Normal), dials back PSM to allow more slip, and adds throttle sensitivity

Edited by Adam B on Tuesday 19th November 09:20

[le_gazman]

jakesmith said:

I'd be interested in this - sport mode does different things on different 911s.... from memory...

On my 997 it sharpens throttle response, allows more slip before kicking in PSM and turns on PSE

In the 997 Turbo sport mode gave you something like 20 seconds of overboost probably enough to get you close to 200 MPH, so without that you couldn't get the full power of the engine. Remap cheaper & can use the power all the time

In other cars sport plus does things like holds gears even longer into redline on PDK and maybe gives an even more aggressive throttle map. I seem to remember from the 997.2 onwards Sport Plus was only really worth it with PDK

I meant just chassis in sport plus mode, but yeah the car becomes a bit of an animal when I hit the sport plus button. Definitely holds you in gears longer in auto and even forces downshifts when braking. Throttle response even from normal to sport is night and day. In anything other than urban traffic I have it in sport mode with sport chassis and the exhaust on. Feels like a much tighter package then.