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997.2 PASM C2S questions....

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Old 07-01-2014, 12:05 PM
  #1
Bruce In Philly
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Default 997.2 PASM C2S questions....

2009 C2S Coupe

Coupla questions.... I understand, at least a bit, how the system works... read the Porsche stuff, examined the diagrams.... but.....


1) Is PASM active or is it just on/off? It seems to adapt to my driving speed. Going slow on really bumpy surface, it appears to turn itself "soft". Does it constantly adapt its valving like the Cadillac ferro-fluid systems?

2) Does the base 997.2 non-PASM ride harder than the "soft" setting on the PASM-equipped S? I remember the base to be softer riding but my friend who just purchased a 2009 base without PASM says his car rides way harder. Odd (he lives in another state, no way to directly compare).

3) My car, 2009 C2S coupe, is really squirrelly in "soft" when driven hard. Is this normal? When I accelerate hard in a turn with uneven pavement, the car really shimmys around on the suspension (not tires on pavement, but the whole chassis moves around). My 2000 Boxster S was on rails in the same situations and much more "performance" than this thing. Rear engine handling? Normal for "soft"? Michelin PSS2.

I am starting to run my car in with PASM ON more.... as it doesn't seem to be invoked at slow speeds and controls that awuful squirelly shifting I experience when having some fun.

Opinions? Observations?

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Old 07-01-2014, 01:43 PM
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fgv1it
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Hello, Bruce. A couple of observations from driving my cars, a 2009 C4S Cab (with PASM) and a base 2012 Boxster, without PASM:

1) My understanding is that PASM is always on. In "normal" mode when you start the car, and "sport" if you use any of the switches that turn on the sport settings.

2) My non-PASM Boxster rides noticeably harder than my C4S. In fact, even with PASM in "sport" the Carrera rides softer than the Boxster. They are two different cars, but the difference in ride is substantial. I've heard similar comments from other people that have driven cars with and without PASM.

3) Have you checked tire pressures? My Carrera got squirrelly once, and when I checked I found that the dealer had set my tire pressures at 33/36 front/rear at a recent service. I went back up to the standard factory setting of 37/44 and the squirrelly behavior went away. I know some people find the standard pressures too stiff, but even then, Porsche recommends 34/40 for comfort.
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Old 07-01-2014, 04:48 PM
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Minok
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If you have PASM, it is always active - its only a question about which mode. In sport mode the response stiffens up a but, compared to normal PASM mode.

My understanding is that normal PASM mode is more forgiving/softer than pure shocks/springs (a nonPASM car).
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Old 07-01-2014, 07:49 PM
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Like the others have said...PASM is always on...either in normal (soft) mode or sport (stiffer) mode. You can switch modes either with the sport button which will re-map the throttle and relax PSM (stability management) slightly and stiffen up your shocks...or just push the button with the picture of the shock to toggle between normal and sport mode for the shocks only.

The chassis wiggle is because there is a lot of rubber in the mounts on a Carrera based car in the suspension. I suggest you take some air out of your tires. The 37/44 setting is for 4 adults and luggage and is not a sporting way to go around in your Porsche with that much air pressure. 33/36 will be better and you can play with a little less too.

When you tires get around 5,000 miles you will notice the car riding stiffer. This just happens over the miles and year or for some people years and the tires heat cycle and the tread gets harder.
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Old 07-01-2014, 10:35 PM
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utkinpol
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If i get it correctly all pasm is - it is a electronically controlled valve on a rebound. Valve is driven by a solenoid, so it is either on or off. It has comfort valve and sport valve and solenoid chooses either one. If i am wrong, correct me.
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Old 07-01-2014, 11:17 PM
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Bruce In Philly
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Originally Posted by utkinpol View Post
If i get it correctly all pasm is - it is a electronically controlled valve on a rebound. Valve is driven by a solenoid, so it is either on or off. It has comfort valve and sport valve and solenoid chooses either one. If i am wrong, correct me.
That is the essence of my question also.

Is this thing a two-position valve or is there some sort of program that is constantly varying the valve with intermediate positions depending on the telemetry of the car such as in the Cadilac or the other active suspensions systems?

I've asked this question before in a slightly different way.... still no definitive answer.

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Old 07-01-2014, 11:22 PM
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Bruce In Philly
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Originally Posted by mdrums View Post

The chassis wiggle is because there is a lot of rubber in the mounts on a Carrera based car in the suspension. I suggest you take some air out of your tires. The 37/44 setting is for 4 adults and luggage and is not a sporting way to go around in your Porsche with that much air pressure. 33/36 will be better and you can play with a little less too.
Thanx Mike, the bushing issue makes total sense given my experience with other cars. The BMW 5s I drove always had an odd yaw to them and a few sources told me it was these bushings. I just didn't want to believe it that Porsche would soften up a 911 like this.

They are really dumming this car down.

I see folks are upgrading/changing out shocks and springs... but it appears that swapping out bushings seems a whole lot cheaper and can make a nice incremental improvement. Is anyone doing this? Can you point me to some threads or more information?

I will try the air pressure method. I usually run a bit higher pressures simply for better mileage given the huge amount of driving I do.

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Old 07-01-2014, 11:31 PM
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Hunt3R
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Originally Posted by mdrums View Post
I suggest you take some air out of your tires. The 37/44 setting is for 4 adults and luggage and is not a sporting way to go around in your Porsche with that much air pressure. 33/36 will be better and you can play with a little less too.
You're referring to cold tire pressure eh?
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Old 07-01-2014, 11:46 PM
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Default PASM

Originally Posted by Bruce In Philly View Post
That is the essence of my question also.

Is this thing a two-position valve or is there some sort of program that is constantly varying the valve with intermediate positions depending on the telemetry of the car such as in the Cadilac or the other active suspensions systems?

I've asked this question before in a slightly different way.... still no definitive answer.

Peace
Bruce in Phlly
I found this short explanation on the Porsche web site that seems to answer your questions:

http://www.porsche.com/usa/models/ca...nagement-pasm/

It is for the Cayman, but it should do for the Carrera as well. The system is not just a two-position valve; it adjusts the dampers individually and continuously as you drive over a range of adjustment.

As for the discussion on tire pressures, please read the manual carefully. There seem to be a lot of wrong interpretations here. Also, read the decals that are affixed to the car itself, usually on the driver's door jamb.
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Old 07-02-2014, 12:04 AM
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PASM is super sensitive to tire pressure, further exacerbating the tire pressure issue. It's trying to keep the tires in contact with the road, a task made into a daunting challenge when the tires are above 45 PSI and it's one person in a lightly loaded car. Them tires are bouncing up hard, so maintaining contact with the road is more difficult.

PASM in Sport mode stiffens things up and the threshold for any stability management is loosened. You can get looser with Sport mode active.

Turn PASM off and you're own your own as far as nannies watching (stability control).

When cornering, seems best to keep some throttle to maintain weight transfer to the rears. omg... I am not
getting into rear-engine handling.
.
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Old 07-02-2014, 12:51 AM
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Bruce In Philly
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Originally Posted by fgv1it View Post
I found this short explanation on the Porsche web site that seems to answer your questions:

http://www.porsche.com/usa/models/ca...nagement-pasm/

It is for the Cayman, but it should do for the Carrera as well. The system is not just a two-position valve; it adjusts the dampers individually and continuously as you drive over a range of adjustment.
That's it! You nailed it. I always suspected it adapted.... as I noted, when I drive slowly on bad roads, switching it to either position does nothing different. There had to be some intelligence there. As for constantly adapting.... that is hard to experience.

From following Porsche literature for about 15 years or so now, I noticed they are poor describers of their own systems. This is very disappointing as many of us, I suspect, enjoy technology and have a capacity to understand.

Good job,

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Old 07-02-2014, 12:56 AM
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Originally Posted by Hunt3R View Post
You're referring to cold tire pressure eh?
Yep!
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Old 07-02-2014, 11:41 PM
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sjfehr
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From a 2005 teknik about the 987:

4.5.2 Software modules for special
control algorithms
PASM contains five software modules
which are superimposed over 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
as body movements increased. This
results in improved contact between
the road and the wheels and 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 verticalcontrol
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
(brake driving). The advantage
of this is that it enables higher brake
forces to 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.
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Old 07-03-2014, 08:07 PM
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Bruce In Philly
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Default 997.2 Technical Suspension Information

Found a bunch of cool information..... Thanx sjfehr, apparently the tek info you posted for 2005 is the same for the 997.2... see the last line below.

Front Spring strut
The spring strut consists of a double-tube gas-filled shock absorber and a conical
spring, which in turn is adapted to the different vehicle variants.
• Basic Carrera chassis Spring rate: 27 N/mm
• Carrera/Carrera S PASM chassis Spring rate: 33 N/mm
• Carrera/Carrera S PASM sports chassis Spring rate: 36 N/mm
• Basic Carrera 4 chassis Spring rate: 30 N/mm
• Carrera 4/Carrera 4S PASM chassis Spring rate: 33 N/mm
• Carrera 4/Carrera 4S PASM sports chassis Spring rate: 36 N/mm

Front Anti-roll bars
The diameter and thickness of the anti-roll bars have been designed to match the
vehicle’s weight and driving dynamics. The following variants are installed:

911 Carrera
• Basic chassis Tube 24,0 x 3,8 mm
• PASM chassis – Coupe Tube 24,0 x 3,8 mm
• PASM chassis – Cabriolet Tube 24,5 x 3,8 mm
• PASM sports chassis – Coupe only Tube 24,5 x 3,8 mm

911 Carrera S
• PASM chassis Tube 24,5 x 3,8 mm
• PASM sports chassis – Coupe only Tube 24,5 x 3,8 mm

911 Carrera 4
• Basic chassis – Coupe, Cabriolet Tube 22,5 x 3,5 mm
• PASM chassis – Coupe, Cabriolet Tube 23.6 x 3.5 mm
• PASM sports chassis – Coupe only Tube 23,6 x 3,5 mm

911 Carrera 4S
• PASM chassis Tube 23.6 x 3.5 mm
• PASM sports chassis Tube 23,6 x 3,5 mm

Rear
911 Carrera/Carrera S
Basic chassis Manual transmission Spring rate: 43 N/mm
PDK transmission Spring rate: 46 N/mm
PASM chassis Spring rate: 56 N/mm
PASM sports chassis Spring rate: prog. 65/95 N/mm

911 Carrera 4/Carrera 4S
Basic chassis Manual transmission Spring rate: 43 N/mm
PDK transmission Spring rate: 46 N/mm
PASM chassis Spring rate: 60 N/mm
PASM sports chassis Spring rate: prog. 65/95 N/mm

Rear Anti-roll bars
The diameter and thickness of the anti-roll bars have been designed to match the
vehicle’s weight and driving dynamics. The following variants are installed:
911 Carrera
• Basic chassis Tube 18.5 x 2.5 mm
• PASM chassis Tube 18.5 x 2.5 mm
• PASM sports chassis Tube 18,5 x 2,5 mm
911 Carrera S
• PASM chassis Tube 19.6 x 2.6 mm
• PASM sports chassis Tube 18,5 x 2,5 mm
911 Carrera 4
• Basic chassis Tube 20.7 x 2.8 mm
• PASM chassis Tube 21.7 x 3.0 mm
• PASM sports chassis Tube 20,7 x 2,8 mm
911 Carrera 4S
• PASM chassis Tube 21.7 x 3.0 mm
• PASM sports chassis Tube 20,7 x 2,8 mm


PASM
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).

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Old 07-04-2014, 11:48 AM
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Thank you everyone for responding to Bruce in Philly's post. I am the person with the base Carrera in AZ that was saying my ride was much stiffer than his S coupe. We both have coupe bodies and I was comparing the ride during a recent trip East. The characteristics of the ride in Bruce in Philly's car are far better than mine. I guess it pays to get the next model up.

My tire pressure, cold, is 34/40 which rises to 40/44 when hot. During a recent service the Porsche dealer set it to 40/44 cold. I hated it. When heated the tire pressure rose to 40/50. I adjusted it after a few days. I will drop it to the pressure to the 33/36 and see if that makes a difference.

Once I digest all your learned commentary here I will decide what I should do, if anything (cost is a concern) to make this ride less kidney jarring. I actually like it most of the time but on a recent 420 mile ride there were some really bad roads and conversation was difficult on them.
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