RonCT

Double post - here and Racing / DE...

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!

nkhalidi

A few thoughts:
1) What makes you think the alignment was perfect? Instability under heavy braking is a prime indication of out-of-whack alignment, might be a good idea to double check.
2) Check the shock settings. A bouncy rear generally means too much spring and not enough shock, but it's hard to give a diagnosis without actually riding in the car. Are Damptronics double-adjustable? If so, dial up the rebound while leaving the bounce static.

BTW, those 19" Fikses you're selling are gorgeous; wish I could justify a set of 19" street wheels for myself!

RonCT

The shop that did the alignment is extremely well known and capable. I posted the alignment specifications here at RL and received major kudos for them getting everything "technically" right on (corner balance was within 2 lbs of optimal, which is not easy to do). So I have confidence in the set-up, just not that the shocks / springs are matched well. Here's the problem with Damptronics / PASM - you cannot adjust the shocks at all. You can't re-valve them either. You can, however, possibly remove the Damptronic springs that Bilstein matched up and try something else. The shop owner suggested that he felt these Damptronic set-ups and / or PSS set-ups tended to over-spring in order to give the buyer the feeling that they've made a significant change (to justify the expense). Maybe I'm not the typical PSS / Damptronic buyer - where I am less street oriented and more track oriented? I would say that at lower lap times, the system felt just fine - say at a 1:06 warm-up lap, but once I started pushing to 1:04 and 1:03, it got worse and worse - so much so that I wouldn't even attempt 1:02s or below because of the uneasiness.

brendo

my conclusion is i'll take my time deciding this and start with sway bars....

lig

Subscribing. Thanks for posting - it's good to have data from someone serious vs. the "I just installed xyz mod and the car feels like it's on rails"

If I ever make this car my go-to lapping day car I think I'd start with Motons.

Targa Tim

Hi Ron,

going a bit off topic here.

How is your lap time with the GT3 compared with your ex-997S? I am fully aware that the GT3 drives and handles better, but how much advantage in lap times are you seeing.

The reason I asked is that I track less than 5 times per year in intermediate level. Money aside, I cannot find a legit reason for myself to upgrade to a GT3. What's your thought?

RonCT

Won't be able to answer sufficiently until I have more time in the GT3. I only had 1 event at WGI in the GT3 and that was with a totally messed up alignment (now fixed) and stock pads. Nonetheless, my first day in the GT3 at WGI with those handicaps gave me faster lap times than the 997S ever gave. Again, that's with a totally new-to-me car that has issues.

Don't bother changing to a GT3 if it's a couple of seconds off a lap time you are looking for. I changed for a variety of reasons...

Carrera Mike

Hi Ron,

I know this is old, but its a "good read" for me. I want to lower the car a little and these Damptronics are the only way to lower and still keep the PASM. Anyway, thanks for posting. Really makes me believe that Porsche got everything sorted out, and for me to just leave it alone

By the way, I was the one who almost bought your Blue S

jrgordonsenior

Ron the change in spring rates in the Damptronics is not significant enough to upset the car under braking as you described.

My first thought when I read your post was that the most probable cuplrit was the change is tires and wheel size. The 19' MPSC's are not great tires, while the 18' RA1 are. I would switch back to the Toyo's and test the data under like conditions without changing anything else. I'll bet even older RA1's will feel better and more stable than new MPSC's....

RonCT

The car is long since traded in on this GT3... When I had the 997S I ran both 18 and 19" wheels and tires on it and had no problems... The technical people I consulted with suggested a combination of the damper / spring rate and rear sway were an issue at my level of driving (ie: Lime Rock - 1:05 was fine, 1:04 started getting uncomfortable, 1:03 was chaos - where bone stock 1:02 was fine).

GreggT

Reviving this thread Ron ..... I'm curious if you were successful in sorting these issues out.
How bout the 'sproing' sound?
Also, can I ask how you arrived at ride height & front-rear rake?.... I've seen pics of your car and she looks excellent.
I have Damptronics going in a 997.2 in next week or 2 when she's delivered. I've been looking for height numbers on 997s from Porsche. I've used that data on 996 (GT3, Turbo, and all). On the 996 chassis, there are the front-rear points we take those measures .... but have not heard if those 2 points are the same on the 997.

I know I can just go on appearance as well as before-after measures ... but also know all those numbers were published for 996 and regarded to have some impact on performance handling .... so I took them to heart on the Turbo which I track ..... and believe she's well sorted out.

TIA for any final tips on Damptronics.

RonCT

Sproing was installation error, easily fixed. Ride height and alignment - I'm not a technician, so I trusted it to the shop. I'd say that if you aren't having the install done at a well respected race preparation Porsche shop, try to find one and have it done there. When I posted the alignment on my car, racers in the know responded with "Wow, that's perfect!"

GreggT

Thanks Ron.
The shop advice is always good.
I've worked with Kelly Moss Motorsports for some time ... good people ..... but I enjoy understanding & being involved as much as I can ... (and they expect me to be a pain in the butt)

mglobe

Continuing this thread for the sake of discussing suspension setup. I recently installed a "track" suspension in my 996 track car. GT3 control arms, toe links, and sway bars. Cross Competition coil-overs with 600/800 springs. FWIW, First time out, my experience with braking was similar to what Ron described. I softened up the rear sway, and it made a significant difference.

RonCT

The twitch was pretty bad and the rear H&R sway was not adjustable. On my "now" GT3, I had to soften up the rear sway to full soft (1 of 3) and the front is on 3 of 5 and the balance is back (rear was on 2 of 3 and it was twitchy, on 1 of 3 it's now nicely planted).

In the end, I liked the original sways and maybe the Damptronics with the OEM sways would have done the trick. Again, with my 997S when I had it, at a 1:05 lap at Lime Rock, no problem, 1:04, was getting twitchy, and at 1:03 I said "uncle" (where with OEM suspension and sway I was at 1:02 and improving).