PASM failure... Ouch

The return of Marty Wild · 12 Aug 2019

So as far back as the 9x7 era, the PASM was doing more than just two damper stiffnesses?

deMort · 12 Aug 2019

I've always assumed as its an active system that they adapt to various road condition .. it's not something i really need to know in depth so haven't investigated it ....

i had a brief read of this file and it mentions a map based on conditions along with various other things it alters for ..

To me that would indicate it continually alters and is not a set soft or hard .

Hertsdriver · 12 Aug 2019

I doubt they could have got away with calling it 'active' if it were just running off of a set map.

jonttt · 12 Aug 2019

My understanding:

Oem PASM Controller = active adjustments but same for all 4 corners

DSC PASM controller = active adjustments to individual wheels and its programmable with provided PC software

I've been playing with the DSC software and it's great fun. The only real thing you have to be careful with is not to set a range past softest setting or you can overheat them

deMort · 12 Aug 2019

As below .. i'm afraid i don't know this system inside out so just post what Porsche have said ..

My guess is the aftermarket unit and the Porsche unit just have different maps :dont know:

99pFlake · 12 Aug 2019

PASM is a semi-active suspension setup as it allows variation of the damping characteristics in response to the vehicle's dynamic changes.

Fully active systems can adjust both the damping and the spring rate of the vehicle. Off the top of my head, the only fully active suspension setups available today are Mercedes' Active Body Control and the setup on the Audi A8 (the former uses hydraulic pistons to effectively move the suspension top mount while the latter uses electric actuators that apply a force to the lower suspension knuckle at each corner).

In the case of PASM on the 997, there's a solenoid in each strut that varies the bypass around the main damper valve. I'm not sure if it's continuously variable or whether it just permits a firm and a soft damper setting.

jonttt · 12 Aug 2019

:thumb: looks as though the oem does have individual wheel adjustments then using a predefined input maps

They must use different inputs as well as maps, at least in pre 9x7.2 cars, as you have to fit an accelerometer for the dsc (already fitted to .2 cars)

99pFlake · 13 Aug 2019

A little update - it looks like PASM in the 997 is continuously variable (as opposed to some other systems which allow switching between a set number of damper settings).

jonttt · 13 Aug 2019

These are the variables used for the aftermarket DSC PASM unit, programmable by PC software......

In simple terms it works from the main table "Shock Calibration" which you set 2 maps for eg Normal / Sport. This sets a "min" and "max" damper setting for each wheel with a gradient between eg what setting at 10%, 50%, 80% etc......

You then use the other tables to alter how those "inputs" relate to the "shock Calibration" table eg G force, if you going around a fast right hander and the G force is X how should each damper be set left front 50% = look up 50% on the "shock calibration" table........ it gets complicated when you the factor in the other inputs eg braking..... but in practice it seems the main thing to tinker with is the main "shock calibration" table and rely on the default factors already set of for the variables, probably unless you are fine tuning for track when you can record the results and compare etc......

So with the DSC you can "see" how the dampers will work and the variable factors, with the OEM its a sealed box you can't tinker with. Most seem to think the OEM "normal" is too soft and "sport" too harsh. The DSC makes the "sport" more useable on the road but I think "normal" is now too harsh (for a 987) and so thats why I'm playing around with it. THe beauty is the way the "shock calibration" table works means that you don't need to have an even gradiant between the softest and hardest setting and so you can setup a sporty mode which is more compliant at lower variables and changes more as the variables get more extreme ie best of both worlds. I think that is probably the main difference with OEM ie can offer a more compliant ride until its really needed and then it can automatically offer a more sporty ride within the same map.
Great fun playing around with it (any excuse for a fast road run lol)

My car has 64k on the clock, has a clean OPC bill of health and the suspension seams spot on. Its good to know from this thread that you can buy a full replacement system which is slightly improved for reasonable money when / if needed...

The one thing I have not really had chance to research is how the PASM damper control actually works physically. What I have established is you have to be careful in what you set as the "softest" damper setting ie it is 1500mA ie if you set 2000mA there is a risk the damper can overheat. It therefore assumed that the damper was therefore controlled by passing an electric current through some form of magnetic damper fluid, that current influencing the viscosity and thefore the damping ability of the fluid ie infinitely variable between its "softest" and "firmest" viscosity ?????? a post above implies is via a mechanical mechanism ??????

Every day is a school day and I'm getting as much out of learning about PASM as I am from driving the car :grin:

99pFlake · 13 Aug 2019

On continuously variable dampers there's usually a solenoid that varies the size of the flow restriction on the valve at the bottom of the damper piston. The overheating is caused by the solenoid being switched too quickly.

What you're describing is closer to the magneto-rheological dampers that Delphi originally offered - they have an electromagnet that surrounds the oil passages in the piston valve and have a ferrofluid instead of conventional oil. Applying a magnetic field causes the fluid to become more viscous and thereby restricts flow.

tuscanracer · 13 Aug 2019

new shocks

Just had my new to me c4s in @Paragon for my first servive and some extras, upon getting the car on the ramps i was called back into the workshop and shown how on both front shocks the chrome shaft at the top underneath the rubber had completely corroded and was a straight MOT fail! Near enough £500 a corner plus some top mounts and new trailing arms front and back my bill had tripled.
On a plus note the car drives like new and feels much better even after dropping on Eibach springs and running 20's

89,000m

deMort · 14 Aug 2019

Mot rules on a shock failure ..

A. shock Absorber :

i. insecurely attached to chassis or axle.

ii. Missing or likely to become detached .

B. A shock absorber damaged to the extent that it does not function or showing signs of Severe leakage .

C. A shock absorber bush excessively worn .

The current rules regarding what can and can not fail an mot on a defective shock .. just for info .

PASM failure... Ouch

The return of Marty Wild

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