RonCT

I'm analyzing TraqMate data from Thursday's DE at Lime Rock and trying to rationalize the "fact" with my "feel" from the event. Generally, the car "felt" much faster, but in the end was not - in fact it was a little less quick around the track. The "feel" part is that the rear end was twitchy, especially in hard braking and cornering. So while viscerally, the car felt a notch above stock, it really wasn't. And that feel of speed (and therefore less stability) equated to slower lap times.

The rear feels bouncy even on the street - the entry road to Lime Rock are a few speed bumps. When I went over them and the back tires cleared, the rear end bounced a couple of times (never had that happen before).

The equipment (listed in another thread) is the Damtronics for 997S, GT3 front sways (2nd from soft) and TRG drop links, H&R sway on the rear set on soft. Ride height lowered about 20mm - alignment was perfect. Wheels and tires changed from 18" RA1s to 19" Pilot Sport Cups - perhaps the change in sidewall impacted compliance?

TraqMate data shows cornering loads were basically equal before and after (Right Load 1.575 G vs. 1.520 G before, 1.606 G vs. 1.602 G before), braking force was less now (1.125 G vs. 1.238 G before) - makes sense - I couldn't get maximum braking due to the rear end.

I really expected some significant improvement, and instead feel I am seeing a decrease in capability.

Any theories on what's going on? Can this be related to sways, the coil-overs, or both? Is it possibly the spring rates in the springs provided with the Damptronics?

Thanks!

38D

Have a faster driver take a few laps so you can gather some comparison Traqmate data and ask their opinion.

SundayDriver

Assuming the spring rates yo choose are known to work reasonably well, you have a shock setup problem. First, how do you know the shocks are any good? Are they new or used? Did you manually move them to feel if there was similar feel across the shocks? (I only ask that as you can waste a lot of time chasing a blown shock.) Beyond that, from the sound of it, you need more rear damping, especially rebound.

That begs a few more questions...
Who choose or set up the shocks/springs? (Were they set up by someone on a scohck dyno or was it a case of 'these are known to work on your car'?
Handling - How did the car behave other than under braking? Was it under or oversteering on 1) corner entry, 2) mid corner & 3) corner exit?
I don't know the track - are there any esses? If so did the car settle quickly or did you feel like you were waiting for the car to set so you could change direction?

RonCT

Finding a quicker driver may be difficult - in the Black run group people are less likely to take laps in somebody else's car, especially if asked to really push the car hard to gather data (liability issues). I was running consistent 1:03 laps at LRP - not close to record setting, but only 2 cars that passed me all day. One was a 996 GT3 Cup in full race preparation and the other was a race prepared 996 TT and neither driver has 997S experience to be able to offer an opinion on, especially at that pace. I know the platform and what the issues are, I just don't know the technical aspects to know what is causing the uneasy rear end (shocks, springs, sways, etc.) that I sense is holding the car back.

The Damptronics were brand new from Bilstein. There's no way to "select" dampening rates or springs - it's a combination package that's made for the 997S with PASM. This is not your typical PSS setup and I wasn't looking for a track-dedicated suspension. I was looking for superior to stock with true coil-over threaded bodies so I could lower and corner balance. This is a street / DE car. Car was understeering as usual - I thought dialing in more camber to -2.3 (from -0.75 stock to -1.6 with GT3 control arms mid last season) would remove some of that, but it didn't. There are quick transitions at Lime Rock and the car settled in better than stock - less roll for sure.

In the end, the Damptronis may not be superior performance wise to stock given my level of driving on the track. Maybe they are more street oriented than I expected? If it's a problem with rear shock dampening, then there's no hope as that cannot change (it's fixed, electronically controlled). If it were springs, then maybe that could be changed, and if it is sways, then that could easily be changed:

1. Return to stock.
2. Remove GT3 from front and put matching H&R on.

SundayDriver

The ability to set up a car is a pretty advanced stage. Once a driver makes it to the higher run groups, they usually have the experience to start learning this. I suggest that you need to put such a driver in your car to do some laps. Someone who has the experience and feel for shocks and other set up items will not need to drive at 10/10ths. A few laps at 9/10ths will quickly tell that person what the major setup issues are. Fine tuning requires that you push the car to the point where you will drive it, but your problems sound bigger than simple fine tuning.

IMO, you have a serious rear shock issue - mostly evidenced by the braking problems. Overall under/oversteer can be tuned a lot of ways - springs, sways, F/R camber and tire pressures. But if the car is getting light in the rear under braking, that is all shocks and there is no workaround for that if you cannot change damping rates. Until you can do this, you might call the vendor and tell them of the problem and see what they can offer. They might be willing to revalve the shocks to something that will work better for you.

RonCT

Thanks for the insight. I have a feeling then that there's no hope that these will do what I hoped they would. You cannot re-valve Damptronics. It's an infinitely adjustable electronic dampening rate system, just like the OEM PASM is. Sounds like in order for me to find a superior system to OEM PASM, I am going to have to give up the PASM feature, put on some JIC or other shocks, and deal with the "PASM ERROR" light on the dash when the ECU doesn't find the electronically controlled shocks.

mglobe

This is pretty disappointing if it remains unchanged. Maybe it would be worth contacting Bilstein directtly? They might have some insights into setup.

SundayDriver

I didn't realize they were self adjusting. I would start with a call to supplier. In the past, FVD has sold a lot of Bilstein packages and done their own valving. You could try chasing down FVD (I would try Schatz Motorsports if they are still around) and see if they have any insight into this package.

Good luck.

RonCT

Here's a photo of what the Damptronic system looks like. I'll admit that I had the PASM set to normal because of how rough Lime Rock is. In October I experimented with PASM and found normal was superior to sport because the softer setting helped absorb the bumps better and left the car better planted. At Watkins Glen the opposite was true - sport was superior. So for this first event with the new Damptronics, and after street experimentation, I left it in normal.

38D

Ron - just out of curiosity, how come you aren't driving your fully track prep'd 964 instead?

Veloce Raptor

+1

RonCT

Just trying to decide which car to focus on, so I figured I'd take my street car one level higher.

mdrums

All the 997S cars that DE with me are either on stock suspension or they go with Cross or JIC coil overs and disable the PASM error light at the Porsche dealer with the PWIS tool.

RonCT

Spoke with some nice people at Bilstein and my thoughts were basically confirmed. PASM is driving the issue here. Damptronics have stiffer springs, but the computer is still in control of dampening. At LRP last week, warm up laps in the 1:07 range were fine, by 1:04 the back end in hard braking was moving all over. 1:03 was very unsettled, so I didn't push any harder. That compares with 1:02 being rock solid with the OEM suspension in October. I didn't try Sport setting because in the past, Sport is what unsettled the car on a rough track so I expected that would make it even worse - in hind sight, I should have tried part of a session in Sport mode just to confirm.

So, conclusion so far is Damptronics are nice in that you can lower the car properly, but the ride is inferior on the street and there's no apparent gain once you get to 9/10 of the car's capacity. Up to 8/10 the car feels very nice on the track, but once you go to the next level, the dampening can't keep up.

Larry Herman

One other thing that you may want to try too is to go back to the 18" RA1s (if you can). It will give you a better baseline for comparison, and you may find that the 19" wheels w/MPSCs are less tolerant of alignment variances than the 18"ers would be.