I just picked up a DSC box and 3-axis accelerometer for my 2006 C2S. The install went smoothly. The PASM light on my console is responding as expected - solid, blink twice, or blink three times modes. I'd like to verify that the accelerometer is functioning properly for all three axes. How would I do this?

I have Durametric Pro and a few bluetooth OBDII transmitters for Android apps like Torque if this helps. Ideally I'd like to see realtime xyz data on either my Android tablet or Windows laptop.

Thoughts?

 

Update: the PASM light behaves the same with the accelerometer plugged in or unplugged, no error codes or weird blinking light patterns as would be expected. Now I'm not sure if I spliced in the accelerometer properly at all. Does the DSC box even work at all in a 997.1 without the 3-axis accel?

 

You should contact Tom at TPC. My guess is you're good to go if the PASM lights are working as they should.

 

As long as your placement is in the center of the car (meaning center from left to right), it should be a fairly obvious difference when you lift off the throttle and when you step on the throttle as well as when you step on the brakes. The car remains noticeably flatter than it did before. I have a Cabriolet and The accelerometer is slightly to the passenger-side of center. I still think it's amazing but could be improved by moving the accelerometer slightly to center. However it was an absolutely noticeable difference in the behavior of the suspension right away.

 

I used Doorman quick splices instead of soldering in the 3-axis accelerometer. Crimps are reliable when done right but I'm second guessing if I should have soldered it in instead. So I want to verify the added 3-axis accelerometer is responding. Remember the 997.1 has a built in 2-axis accelerometer. Here's why I want to confirm everything.

I'm lowered on Bilstien damptronics, upgraded H&R sways, GT3 LCA's with solid pucks, solid monoball ends and increased camber. The suspension is fairly stiff to begin with. I also have a front lip and Techart rear wing too, which keeps the nose and rear planted at speed. Basically I do not have a lot of nose dive on braking to begin with, but some. After doing the install yesterday, I had the car out for a long drive and could definitely feel more "rails" on carving turns. The best way to describe it is like trying parabolic snow skis for the first time, more planted carving turns. The console PASM light is responding as expected so the DSC box is functioning. Honestly I didn't notice a huge difference in nose dive though probably because of all my other suspension mods. But I did notice a difference when turning left and right.

So as a test, I unplugged the 3-axis accelerometer and went for a second but short test drive to see if anything changed. The PASM light still responded as expected verifying the DSC box is working even though the 3-axis accelerometer was unplugged. The few turns I took felt stiffer than the stock PASM box. I just have no idea how the DSC box is supposed to respond in a 997.1 with only the default 2-axis accelerometer installed (ie. no additional 3-axis accel).

Tom at TPC-Racing, are you around this holiday weekend?

 

Gratiuitous shots from yesterday morning to make this thread more interesting

 

The DSC box won't work without input from the Accelerometer even if the PASM switch lights change when pressed If you do a test run with the OEM box and with the DSC box and feel a difference through turns (like you described "more on rails") then your Accelerometer is installed correctly. If it's not installed correctly or it's not working correctly you'll get weird gauge behavior and lots of strange dash light behavior as the Accelerometer can effect the entire CAN/BUS communication network.

I tapped mine in during the install without soldering and it works fine so as long as you've made good connections to the proper wires, you'll be fine.

 

DSC will still change modes(as far as the LED light goes) when the 3-axis accelerometer disconnected. But without signal from the 3-axis accelerometer the system defaults to full stiff. DSC does not use the signal from the OEM 2-axis accelerometer at all. When the user software is released later this year, the software will show the g-force data via laptop computer screen. For now, you should be able to feel the difference between DSC mode 1 and mode 3 driving over bumps. With the accelerometer unplugged(system defaults to full stiff) will ride significantly stiffer over bump than properly functioning DSC mode 1.

It is possible that if the ride height to too the suspension is riding on the bump rubbers. If this is the case, DSC won't make much difference to keep the nose from diving under braking because the nose is already being up by the bump rubber.

I'd try this- With accelerometer plugged in and in mode 1, go over a set of bumps to get a feel. Then uplugged the accelerometer and go over same bumps at same speeds to see if there's a noticeable difference.

 

Actually, looking at your photos the ride height isn't low enough to be on bump rubbers. Looks to me there's about an inch gap between top of the front tire and fender arch. If the front sway bar is set to full stiff that'll take away some of the difference that normally distinguishes DSC mode 1 from mode 3 because the stiff bar setting is holding the chassis up. In which case, even if you notice only a slight difference between mode 1 and mode 3, the system is working. If that's the case perhaps try softening the bar to allow the shocks to do more work.

 

Thanks for the reply Tom. I will be testing today on a stretch of road with the warning grooves on the side.

Some requests for future box firmware upgrades:
1. Mode 0 with the light off - defaults to OEM "normal" static mode on the 997.1, all four corners fixed at a low stiffness setting just like the stock "normal" mode
2. Mode 4 - OEM "sport" static mode on the 997.1, all four corners fixed at a high stiffness setting just like the stock "sport" mode
3. Fast blinking error light if the 3-axis accelerometer cannot be found, would help trouble shoot a bad install

 

OK, the box seems to be working. I'm not seeing a lot of vertical vibration damping between the three settings but I definitely feel the stiffening up during carving turns. I swapped back and forth a few times to confirm everything.

With the stock OEM PASM box and my modified suspension, normal mode is fairly stiff with neutral handling. Sport mode is almost undriveable on straightaways except on the smoothest of roads. Bilstein damptronics, engine mounts, monoball LCA ends, solid LCA pucks, trans mounts and upgraded sways all lead to my stiff suspension. My rear sway bar is set on the 2nd hole from the end (2 out of 4). With my setup and the stock PASM box I always leave the PASM button turned off.

With the DSC box all three modes are driveable on straights and turns are nice and crisp. Mode 1 is a hair soft on entry to a turn but stiffens up quickly. I find myself driving in mode 2 most of the time now. It's hard to gauge exactly how smooth/rough straightaways are compared to OEM normal mode, but it is definitely softer than OEM sport mode.

Bottom line, I get dynamic stiffening on each corner as needed on turns without sacrificing driveability on straightaways. It's like having sport PASM mode kick in only when needed on turns. It's a keeper!

ps. Thanks for your help Tom

 

Yes these additions would be a good idea. Just to correct, the original PASM modes are not actually fixed damping, they do have a range of damping forces useable by the system, which overlap in the middle somewhat.
There is also 5 extra "modules" :
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 program, 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 unresponsive driving
behavior. In the Sport program, 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 program,
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 program was
previously decreased by the verticalcontrol
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.
Principle of the PASM map-controlled
damper:
Conventional shock absorbers cannot
actively adapt to changing driving conditions.
As such, the damper design
always represents a compromise between
comfort, sportiness and loading
state. Neither can they take into consideration
the individual driving style.
Unlike conventional dampers, the PASM
map-controlled damper also has an electrically
actuated hydraulic bypass valve.
The damping effect is provided by the oil
in the damper flowing through an opening
when the vehicle moves. The smaller
the opening cross section, the harder
the damping.
With the PASM damper, the oil can flow
through a bypass valve as well as
through the fixed opening 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).

 

Very nice write up floatingkiwi. To clarify, you are confirming that the PASM is an analog control on the variable valve. I gather there are no rheomagnetics adjusting viscosity.

 

Yes. I can send you the whole doc if you like? about 4 meg. I've hoarded all sorts of interesting files!

 

There has been a lot of discussion on this in the past. I am sure I'm not the only one who would love a copy of that information! Thank you for the offer. Do you have a link, or would an email address be better?