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I had the unique experience of installing/road testing the Tractive DDA coilovers on my 997.1 GT3 during the week. I should mention that the previous coilovers were Bilstein GT3/RS/GT2 B16 Damptronic with 500/720 in-lbs springs. With DSC module controlling the B16's I had no complaints whatsoever using Mode 1 for street and wet track, and Mode 3 for dry smooth track. In fact, it was great. So, I was a bit reluctant to make the change since I was very much satisfy with what I had but the thought of having superior build quality shocks with minimum stiction that responds 17x faster, with double the dynamic range and better coil springs was too appealing not to do it. I knew 100% for sure the Tractive DDA's performance will surpass the B16 in the higher load ranges but will the car ride as good or better on bad roads is the question in my mind.
The springs on the Tractive DDA are 392/728 in-lbs. They are Swift brand springs, Swift's primary unit of measurement for their spring rates is kgf-mm in whole number increment. In this case the springs are 7.0/13.0 kgf/mm(which converts to 392/728 in-lbs). Here's more info on Swift Springs if you want to get all geeked out like I do -http://www.swiftsprings.net/tech/advantage.html The Tractive DDA have such a wide dynamic range that they will work with a range of spring rates depending on what the driver is wanting to achieve.
I did the installation on the parking lot of shop because the shop is completely packed full of cars. Despite of the sporadic heavy downpour throughout Saturday, I was determined to get this done! I didn't get started until late in the afternoon because I drove around for a while on good roads and bad roads on the B16's taking mental notes on how the car felt. And then it took a while to gather the tools needed, measure the ride height(to duplicate later) before getting started and then have the car on stands on the wet parking lot. Here are some photos.
I had the all four corners installed just before the heavy rain. With the adrenalin pumping to get it done before the sky opens up I forgot about the Tractive DDA requires different DSC programming for the much wider dynamic range. I called Mike Levitas, he said: "You can drive home as is. It won't work as intended but it also won't hurt the shocks. Come back to the shop tomorrow morning and I'll program your DSC for the DDA."
Part of the unique experience was driving the 20 miles home with the wrong DSC program for the DDA shocks. It made me truly understanding the meaning of the phrase much wider dynamic range. The DSC program(or mapping) for Bilstein PASM/Damptronic maxes out the shocks' stiffness quite frequently and was mapped in consideration for the nominal stiction and reaction time. With the wrong program, the DDA shocks got VERY stiff(like driving a Cup car on bumpy paddock) at times at times, and the transitions from stiff to soft was so incredibly "crisp"(that was the first word that came to mind) its like as if I was feeling the difference in milliseconds of reaction time, which I knew I wasn't, but definitely was a neat feeling. The changes to damping rate gave ultra precise feedback. Later on I spoke with a Tractive Engineer, he said what I felt was the reduced stiction.
The next morning, I drove back to the shop to reset the ride height for the springs settling-in. Mike arrived just as I was making the small adjustment and he installed the DDA program to my DSC module.
With the right program the DDA's totally rock in the mid and high load ranges. Its hard to explain how the chassis can have more support while being more compliant over bumps on long sweeper exit ramps. At the lower load range, bumps below 35mph, some of the bumps felt better damped than before while some felt more stiff depending on the shape of the bump. Keep in mind this this is compared my previous Bilstein/DSC combo with years of development for road refinement. Even though it is not as good over some bumps as before its still more compliant and way less bounce than stock and all track-oriented coilovers that I've driven. Mike has identified what is happening in this range, what he found was the Tractive DDA's are responding to accelerometer signal(specific to the .1 non-turbo cars) that's below the processing range of the Bilstein. The tiny 0.1g spikes that occurs in <50ms in this range are making the DDA shocks stiffen up. Whereas before the Bilstein shocks just flat lined soft since the signal is below the mechanical operating range and the shocks didn't respond fast enough anyway. Again, this is specific to the .1 non-turbo cars. The .1 turbo and all .2 cars are factory equipped with 3-axis accelerometer that doesn't put out this signal range.
Next week, he'll work on the lower range signal. This will benefit all .1 non-turbo users with Tractive DDA. Mike also recommended that after the software change I should go one step softer on the springs for even better ride and let the shocks do the work to achieve the stiffness for higher load range.
In summary, I really like the way these shocks feel at the higher load ranges and how the wide range delivers the performance. I can wait to feel the improvement in the lower load range. And I haven't even corner balance and aligned the car yet. The alignment is pretty close to where it was before by matching the riding height.
PS- By muscle memory, I am short stopping 20 feet at every traffic lights and stop signs on roads that I drove on everyday as a result of improved chassis management over the previous setup.
__________________
PCA National Instructor
TPC Racing stats:
2023 Porsche Sprint Challenge 992 Cup Am Champion
2023 Porsche Sprint Challenge GT4 Pro-Am Team Champion
2022 Porsche Sprint Challenge 992 Cup & 991 Cup Champion
2020 IMSA GT3 Cup Challenge 2nd Championship
2018 IMSA GT3 Cup Challenge 2nd Championship
2016 IMSA GT3 Cup Challenge Champion
2013 IMSA GT3 Cup Challenge Champion
2006 Rolex-24 @ Daytona GT Champion
2004 Grand-Am SGS Class Champion
Looking forward to a ride. Will you have the car at the shop tomorrow?
Yes! I've been driving the GT3 everyday since Saturday. Have a tick over 200 miles on the new suspension. I can feel a little bit of the linear-rate racing springs but it rides comfortable enough for me to drive everywhere including making pizza run for dinner. The more I drive the more I like it. Eagerly looking forward to Mike smoothing out the 0.1g spikes to make the ride like a stock Audi A4. Right now it's more like a 996 with RoW M030.
sounds like another interesting project- lighter/softer springs should pay dividends in the wet or when cruising. As the shocks are doing more work, I hope they have the thermal capacity not to over heat in the stiffer settings?
sounds like another interesting project- lighter/softer springs should pay dividends in the wet or when cruising.
That's the plan.
Originally Posted by Ur20v
As the shocks are doing more work, I hope they have the thermal capacity not to over heat in the stiffer settings?
The Tractive engineers assured us that won't be an issue based on their full-stroke testing of the DDA valve to 2.4 million cycles @ 212F degrees. The DDA valve was also tested by an OEM manufacturer to 18 million cycles and they approved the valve for production. Closer to home, Mike Levitas has been running 6.0/10.0 kg-mm(336/560 in-lbs) in his 987.2 Turbo Boxster Spyder with DSC and Tractive DDA with great results. I think I'll try 6.0/11.0kg-mm(336/616 in-lbs) for the rear-engine car. I'm loving this since I was starting to get bored with the car.
Amazing what can be achieved with few strokes on a keyboard
I meet up with Mike Levitas at shop at 8am today(Saturday). With a few strokes of keys on his laptop he said take it out for a drive. Its a good time to do this sort of things because the phone lines aren't ringing off the hook and no other routine distractions. I went for a half hour drive purposely running over every bump, expanding joint, and broken concrete- BAM! I am truly amazed at how good the car rides. As good as an upscale luxo/sport sedan in Mode 1. I haven't tested Mode 3 at high speeds yet but Mike said Mode 3 mapping is same as his race-winning Cup car! Enough about me going on blah blah blah. I'll take anyone in the area for a ride!
Its has been awhile since I've posted. Throughout the Summer we have made leaps and bounds of improvement to the DSC/Tractive suspension to a point that the suspension is so hooked up and incredibly easy to drive fast that I need to have proper seats, roll bar, and safety equipment for track use. I have been deferring this step as long as could but it is time.
There's a number of bolt-in roll bars on the market, most are good, I chose DAS Sport roll bar because its one of the bars that meets PCA/SCCA racing requirement. The designer, Colin Dougherty, who's a fellow racer and mechanical engineer has been in the industry for a couple decades. This product has been around a number of years so its a refined product in my opinion. Here are some pics for phase 1 of the project.
Good bye to the comfy heated seats.
I started the installation after work hours on a parking lot. Its October so I don't have much time until the sun sets.
Seats out. Even though I was racing against the sun I took a few minutes to vacuum the rear carpeting and cleaned the inside of the rear window. If I don't do it now it'll be a b!tch to do after the roll bar is in!
Putting the roll bar in was a breeze. Everything lined up perfectly as advertised. No need to elongate any holes or modify anything on the car. I took the extra time to trim the corners of the ECU mounting plate so that should I ever need to remove the ECU in the future, partial removal of the roll bar wouldn't be necessary. With the help of my co-worker Harris we had the roll bar in resting inside the cabin with very minimum time before the losing the daylight. Afterwards I put the car inside the garage and went all OCD torqueing the fasteners over and over again...its a sickness, I know.
I particular like the built-in rear shock tower brace of the DAS Sport roll bar.
This IS the easiest thing I have done on this car; straight forward bolt-on, no setting up nor sorting required, and puts me right on schedule for Phase 2. This is a beautiful thing! Stay tuned for Phase 2.
Last edited by Tom@TPC Racing; 10-26-2015 at 07:31 PM.
Reason: cleaned up grammar
07-04-2015, 03:49 PM
-http://www.swiftsprings.net/tech/advantage.html The Tractive DDA have such a wide dynamic range that they will work with a range of spring rates depending on what the driver is wanting to achieve. 
