PASM - Explained
Discussion
OK
I have a car with PASM.
Alot of people hate it. To the extent of wanting to shot the designer. And his dog.
And thats a quote!
Now, from what I can tell, its a system that allows firm suspension and rock-hard suspension by the press of a button. Yes, certainly on the correct roads/track, said button maybe pressed to the advantage, but as for the active part, I'm confused as there are so many that look down on it as a foible, rather than a benefit.
I'd to know why people see this as such a downfall on the GT3 and why they think it so bad? I am opened minded and prepared to learn!
Stevie
I have a car with PASM.
Alot of people hate it. To the extent of wanting to shot the designer. And his dog.
And thats a quote!
Now, from what I can tell, its a system that allows firm suspension and rock-hard suspension by the press of a button. Yes, certainly on the correct roads/track, said button maybe pressed to the advantage, but as for the active part, I'm confused as there are so many that look down on it as a foible, rather than a benefit.
I'd to know why people see this as such a downfall on the GT3 and why they think it so bad? I am opened minded and prepared to learn!
Stevie
The only real complaint I've heard about PASM is that in Sport mode it is bone-shatteringly hard, leading to people just leaving it normal all the time, and on some PASM-equipped cars the whole shebang (PSE, Sports Chrono revvy mode) is tied to the same button. Think you can re-disengage Sport PASM though after you've pressed Sport, at least in some configurations.
Some might also make the argument that in a track car it makes it unpredictable because "computers are making decisions on suspension stiffness".
The above said however I've never personally seen PASM as a bad thing to have.
Some might also make the argument that in a track car it makes it unpredictable because "computers are making decisions on suspension stiffness".
The above said however I've never personally seen PASM as a bad thing to have.
Steviebeee said:
OK
I have a car with PASM.
Alot of people hate it. To the extent of wanting to shot the designer. And his dog.
And thats a quote!
Now, from what I can tell, its a system that allows firm suspension and rock-hard suspension by the press of a button. Yes, certainly on the correct roads/track, said button maybe pressed to the advantage, but as for the active part, I'm confused as there are so many that look down on it as a foible, rather than a benefit.
I'd to know why people see this as such a downfall on the GT3 and why they think it so bad? I am opened minded and prepared to learn!
Stevie
Full explanation of how PASM works below - copied from Porsche Tech Manual for 997S.1 - It's a lot more complex and sophisticated than you'd think....I have a car with PASM.
Alot of people hate it. To the extent of wanting to shot the designer. And his dog.
And thats a quote!
Now, from what I can tell, its a system that allows firm suspension and rock-hard suspension by the press of a button. Yes, certainly on the correct roads/track, said button maybe pressed to the advantage, but as for the active part, I'm confused as there are so many that look down on it as a foible, rather than a benefit.
I'd to know why people see this as such a downfall on the GT3 and why they think it so bad? I am opened minded and prepared to learn!
Stevie
Porsche Active Suspension Management (PASM)
For the first time in the 911 series, the new 911 Carrera S is offered with a
chassis that has actively adjustable dampers. The PASM is standard equipment
for the 911 Carrera S. In comparison with the standard chassis, the vehicle with
the PASM chassis lies 10 mm lower.
The newly developed, variable damping system “Porsche Active Suspension
Management” helps to do justice to the demands for a modern chassis.
The aim was to maintain the high comfort level of the standard chassis while
increasing performance at the same time.
This technical data is merely intended to provide an overview. As it is subject
to change during the course of the model year, the data published in the
Technical Manual always remains authoritative.
The driver can choose between two programmes: “Normal” and “Sport”, both
are selected via a button on the centre console.
The function light in the button comes on with the Sport setting. At the same
time a damper icon appears in the instrument cluster display together with the
text “PASM Sport”. When the normal programme is activated, the damper icon
appears accompanied by the text “PASM Normal”. The text and icon remain
visible for 4 seconds and then disappear.
PASM combines two chassis rolled into one: One with equal measures of
sportiness and comfort and one entirely dedicated to sportiness and the race
circuit.
Normal mode (the basic setting when the vehicle starts) on the one hand
provides the same excellent comfort as the standard chassis, on the other
hand, the chassis approximates the sportiness of the sports chassis when
regulative interventions are made with active PASM. In conjunction with specially
developed software modules, the PASM ensures excellent performance and
even greater driving safety in extreme situations.
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.
Acceleration sensor
The acceleration sensors are attached to the front right and rear left spring
strut domes, respectively.
The arrangement allows lifting, pitching and rolling movements of the body to
be measured.
PASM control module
In left-hand drive vehicles, the PASM control module is installed on the front wall
(footwell passenger’s side) at the right. In right-hand drive vehicles it is installed
on the front wall (footwell passenger’s side) at the left.
Shock absorbers
Unlike conventional dampers, the PASM map-controlled damper also has an
electrically actuated hydraulic bypass valve (arrow).
The damping effect is provided by the oil in the damper flowing through a piston
valve when the vehicle moves. The smaller the valve cross section, the harder
the damping.
With the PASM damper, the oil can flow through a bypass valve, as well as
through a fixed valve in the main piston. The flow can be increased or reduced
by opening and closing the valve via a slide, producing continuous adjustment
of the damper force.
In the event of a system failure, the valve automatically closes. PASM is then in
the hardest damper setting and thus the safest mode from a driving dynamics
point of view (fail-safe principle).
One observation I would make is that Porsche appear to have tuned PASM quite differently for the new 991 and 981 models. Having driven examples of both cars with PASM, the Sport setting is now much more useable on the road, whereas previously I would only use Sport PASM on the smoothest roads (e.g. in Germany). On my 981, Sport still offers excellent compliance at medium to high speeds, but more body control. Normal PASM is still preferable at low to medium speeds, or when not pressing on.
Cheers
Cheers
And here's the comments from the Gen-2 Tech Manual about the changes made...
Porsche Active Suspension Management (PASM)
As on the previous models, the new 911 models also feature the electronically
controlled damping system Porsche Active Suspension Management (PASM) with
actively adjustable dampers. PASM comes as standard for the 911 Carrera S
models and is offered as an optional extra for the 911 Carrera models.
To adapt to the improved driving performance of the new models, the system
has been modified both hydraulically in its damping characteristics and with regard
to system control. Each single model was considered individually during tuning.
PASM also combines two types of chassis in one on the new 911 models.
A sportily comfortable chassis in its basic setting and a purely sporty one at the
touch of a button in the centre console (PASM damper icon). PASM thus offers not
only two rigid chassis setups, but even within the basic setup, variable damping
adjustment is also available for each individual wheel.
Basic information on PASM can be found in the Technical Service Information for the
911 Carrera (2005).
Porsche Active Suspension Management (PASM)
As on the previous models, the new 911 models also feature the electronically
controlled damping system Porsche Active Suspension Management (PASM) with
actively adjustable dampers. PASM comes as standard for the 911 Carrera S
models and is offered as an optional extra for the 911 Carrera models.
To adapt to the improved driving performance of the new models, the system
has been modified both hydraulically in its damping characteristics and with regard
to system control. Each single model was considered individually during tuning.
PASM also combines two types of chassis in one on the new 911 models.
A sportily comfortable chassis in its basic setting and a purely sporty one at the
touch of a button in the centre console (PASM damper icon). PASM thus offers not
only two rigid chassis setups, but even within the basic setup, variable damping
adjustment is also available for each individual wheel.
Basic information on PASM can be found in the Technical Service Information for the
911 Carrera (2005).
If you are going to drive ten tenths on the track then PASM may not be the best answer for a suspension set up. On the road however in normal mode the ride is better than without PASM and if you are driving spiritedly the PASM will adjust to a better setting in normal mode than a non PASM setup. If you are pushing the car to the limit where you could feel PASM on the road was unpredictable you need to be locked up because you are going way to fast.
Matt Seabrook said:
If you are going to drive ten tenths on the track then PASM may not be the best answer for a suspension set up. On the road however in normal mode the ride is better than without PASM and if you are driving spiritedly the PASM will adjust to a better setting in normal mode than a non PASM setup. If you are pushing the car to the limit where you could feel PASM on the road was unpredictable you need to be locked up because you are going way to fast.
I'd definitely agree with this. Whilst I've read that PASM can be caught-out on track, I've never experienced it do anything to pitch me into the nearest ditch; even giving it the beans in 'Evo Triangle' territory, or through central France on a (very fast and frantic) PN tour. In truth, most people that don't track their cars or haven't taken any on-limit car control courses (like me - but hopefully that will soon be remedied) aren't capable of getting anywhere near 10/10ths on a road (irrespective of how irresponsible an 'ambition' that might be). For us, PASM does a damned good job compared to a 'fixed' setup. More relaxed ride when cruising, damping that adapts as we try a bit harder and Sport Mode to help even more when pressing on. Whilst Sport Mode is generally tooth-rattlingly stiff, where it does really help is to stop the car 'bottoming-out' when pressing-on on lumpy B-Roads - there it's ideal.Edited by Ian_UK1 on Monday 11th June 11:33
I had a 911 GTS with PASM and I thought it did an excellent job of providing a comfortable ride in normal mode and superb handling chracteristics in sports mode when on track. I have done car limit handling and track driving in the car but never experienced the issues that I've read about on various forums. In fact I found the car to be remarkably benign on-limit.
Having said that I think the passive set-up in the CR is extremely well-judged. It's comfortable enough (although not as comfortable as the GTS in Normal mode) and handles mid corner bumps with total aplomb.
If you never take it on track it doesn't sound like PASM is ever going to be an issue and in fact gives you some options when you decide it's hoon time! I found Sports mode in the GTS to be excellent fun on the road when the mood took you and far from the hard riding "don't touch that sports button POS" that many people seem too happy to agree with!
Having said that I think the passive set-up in the CR is extremely well-judged. It's comfortable enough (although not as comfortable as the GTS in Normal mode) and handles mid corner bumps with total aplomb.
If you never take it on track it doesn't sound like PASM is ever going to be an issue and in fact gives you some options when you decide it's hoon time! I found Sports mode in the GTS to be excellent fun on the road when the mood took you and far from the hard riding "don't touch that sports button POS" that many people seem too happy to agree with!
Durzel said:
The only real complaint I've heard about PASM is that in Sport mode it is bone-shatteringly hard, leading to people just leaving it normal all the time, and on some PASM-equipped cars the whole shebang (PSE, Sports Chrono revvy mode) is tied to the same button. Think you can re-disengage Sport PASM though after you've pressed Sport, at least in some configurations.
Some might also make the argument that in a track car it makes it unpredictable because "computers are making decisions on suspension stiffness".
The above said however I've never personally seen PASM as a bad thing to have.
The bone-jarring ride is really a mix of shockingly bad roads and huge, heavy wheels with shallow sidewalls. On my Cayman with std 18" wheels, 'Sport' was very usable on most roads if I wanted to press on. I tried a car with 19"s, and 'Sport' was unusable above 80 mph or so, as the wheels were in the air and the car nearly in the ditch.Some might also make the argument that in a track car it makes it unpredictable because "computers are making decisions on suspension stiffness".
The above said however I've never personally seen PASM as a bad thing to have.
SS7
markiii said:
There is a huge difference between PASM on a gen 1 and a gen 2
Gen 2 is night and day better
Isn't that the truth! Gen-2 damping controls body movement so much more precisely, even in Normal, and eliminates the slightly floaty, underdamped feel of the Gen-1. Feels a lot more secure. Sport mode is firm rather than tooth-rattling and is much more usable. (Foregoing applies to 997S). Big, big upgrade.Gen 2 is night and day better
markiii said:
There is a huge difference between PASM on a gen 1 and a gen 2
Gen 2 is night and day better
I suspect (having only limited miles in 997s) that the system was a more successful application in the Cayman. I certainly didn't recognise any float or damping issues either on the road or track.Gen 2 is night and day better
SS7
Gassing Station | Porsche General | Top of Page | What's New | My Stuff