On the drive home, I noticed the car was significantly louder than before. I expected some extra noise from the transmission mounts, but not this much. After poking around, I remembered and saw that the adjustable camber plates created an open path for all the noise to make it into the cabin from the exterior. On the drive home, I noticed the transmission mounts did break-in. I was getting a rattle from a heat shield or something as I was going on/off the throttle while on the highway. By the time I made it home, the rattle was mostly gone.
At work, I had some leftover thermal and acoustic insulation from the company Soundcoat. This Soundfoam ML UF+ is designed for HVAC applications and it has UL and ASTM flammability ratings.
I jammed in a few more layers to fully take up the gap between the camber plates and the factory foam insulation.
Paradox Performance ended up reusing all of the factory fasteners for the transmission mounts; I didn’t need to buy the bolts that the Rennline instructions said were necessary for the 981 Cayman. But, because I did, I discovered the mismatch issue between the factory bolt flange diameter and the counterbore diameter. As my car was equipped with the active transmission mounts, the DSC controller is needed to not get a fault light due to the factory mount not being connected.
The factory PADM (Porsche Active Drivetrain Mount) is a chunky thing. It has a vacuum line going to it in addition to the electrical connector; the vacuum line on the vehicle side was capped off with the installation of the new mounts. It’s a bit of an odd controls scheme with vacuum being the signal and still requiring electrical power, but there are many solenoids and valves on the car that use vacuum pressure as the signal. Due to this, it’s one of the reasons why I capped off the vacuum line going to the water pump as a failure of the pump would suck coolant into the vacuum system and mess up an untold number of valves and solenoids. The Rennline mount saves a bit of mass compared to the factory PADM which I ballpark at 5 lbs. I’m guessing the Rennline mount is about half the mass. The Porsche active engine mounts are the same part, but they are harder to get to which is why I decided to go after the transmission mounts first. Eventually, I’d like to replace the engine mounts too.
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You can actually get really accurate results using the equation if you have access to the actual springs:
:Using Coil Spring Dimensions and Material Properties
If you are designing a coil or want to find the theoretical rate from its physical build, use the Spring Rate Calculator formula:
Equation: \(k = \frac{G \cdot d^4}{8 \cdot D^3 \cdot n}\)
G: Shear modulus of the wire material (approx. 11.25 × 10⁶ psi for standard steel)
d: Wire diameter (thickness of the metal wire)
D: Mean coil diameter (Outer Diameter minus the wire diameter d)
n: Number of active coils (the total coils that move and flex)
https://www.thespringstore.com/spring-rate-calculator.html
I gave it a try, but a there is a large unknown of material. That said, I feel like the numbers the online calculator generated are about 60% above any reference numbers I have found for other generations and models of Porsches. Any numbers I post are just pure speculation, so I’ll just stay quiet on them. I could bust out my old college textbook and run numbers myself, but the unknown material is still a big uncertainty. Key observations of the factory coilovers, the rear is a linear rate spring and the front is a progressive. On the assemblies, Porsche labeled that the springs are under 1000N of load.
Do you have the old springs still? Apparently you can actually measure them. I found this old forum post:
“CC, the variables you listed are what makes a spring…spring. When I was involved in IMSA and NASCAR, I tested each spring before it went on. The reason was that even a spring from a very well established company could be off by as much as 5%, which was too much for dialing in a suspension. Sometimes the error was due to the spring being bent because of a wreck. Usually it was just off. It didn’t have to be out much to be off. Evenly wound coil springs are very linear. To sum it up, you can either trust the manufacturer to be close, or test them yourself. Put the spring inside a PVC pipe slightly larger in diameter and set on an accurate bathroom scale and zero the scale. Using a push rod like a wooden dowel, push down until the spring compresses 1 inch and read the scale. These springs are rated kg/mm so there will have to be a conversion from lbs/inch.”
I also have a 718 with swift linear springs in the same rate, 70 up front and 80 in the rear. Mine are on B16s so not as exciting as your Tractives. For me the biggest improvement came when I added low speed rebound damping to my DSC to compensate for the heavier springs.
Looking forward to your extended review of these as dual duty and what changes you make to the tune long term.
What is the operating mA range of the B16s? I bet they are quieter than my TracTives. It was a bit surprising to me how ‘loud’ the car is going over bumps with the full spherical setup and the TracTives. My S2000 was still basically quiet with the full spherical control arm setup and the KW Clubsports. I think the strut suspension setup on the 718 chassis transmits more shock loads into the chassis compared to the control arm setup of the S2000. I do think the spherical bearing adjustable camber plates of the TracTives is a major contributor to the noise over bumps and they may just be due to the bearing sizing selected.
I have another significant change to the turbo and exhaust setup coming in stages. And I will need a new tune. The new setup from Raggdoll will have better response and I think the same or better power and it’s all bolt-on. I designed a new exhaust tip to replace my x-pipe too which will flow better.
Damper operating range
• OEM dampers – 1500mA is full soft and 500mA is full stiff.
• Tractive dampers – 1900mA is full soft and 500mA is full stiff.
The OEMs and B16 are both made my Bilstein and are the same valve. For a Non GT4 owner the B16 is a fully threaded coilover with a an inverted body, very similar to what came on GT4s.
A friend of mine in another 718 has the Tracitves and also complains about the same noises, I have not ridden in his car long enough to get a feel for them. He said he is suspecting the mounts.
One thing he loves about the tractive is its ability to bomb over the curbing in the corners on the track, the car does not get upset or wiggle at all. I did notice in his calibration that he does not have as much compression damping as I do. Seems the the next step for me is to try taking some compression out of my car and see if it is more compliant over bumps and curbs.
What I did to be more compliant over the sharp bumps during street driving is take out high speed compression in the velocity tables. I did -5/-3/-1 on the front compression hi/med/low. I did around -3/-2/-1 on the rear.
That is a great reference!
Currently my friend with Tractive is at:
Front Comp 3/3/5 reg and 5/5/5 sport
Rear Comp -5/-5/- reg and -10/-10/0 sport
Front Reb 10/15/20 reg and 10/15/20 sport
Rear Reb 5/10/15 reg and 5/10/15
I am at:
Front Comp 10/7/7 reg and 12/12/7 sport
Rear Comp 10/7/7 reg and 15/15/7 sport
Front Reb 20/20/15 reg and 25/25/15 sport
Rear Reb22/22/15 reg and 28/28/15 sport
Note that the high speed does not come into play on the stock and B16 valve due to the slower response time.
If you email me at s2kmanifold@gmail.com, I’ll send you the calibrations I made for the factory SPASM setup and my Tractive setup as a reference. No clue if they would be any better or worse to your prefrences in handling.
Yours and your friends calibrations lean heavily on the velocity tables and I think the values would act to reduce the rate of roll and pitch. Reminds me of how enzocat on Rennlist liked to do the calibrations. I kept my values much more mild. I tweaked the rear values to eliminate some turn-in oversteer I was getting and I took out some high speed compression to reduce some of the sharp bump impacts.