I love the relative everyday usability of my car. People ask why I didn’t get a GT4. Aside from the $50k price difference when you take into account the Porsche dealership price gouging, er, ADM, the low frontend of the GT4 would not have survived this driveway.
I went on a highway cruise and I wanted to see what kind of mileage I could get. With the cruise control set to 70mph, the car managed just over 32mpg.
On the way home over the same stretch of 405 and the cruise control set to 65mph, the car did over 36mpg. If I set the cruise control to 60mph, the car could feasibly do close to 40mpg which is pretty solid for a car making as much power as it does.
If you go back to Part 1 and read the last paragraph, I said this, “So what is my build plan? I am going to follow the same basic recipe as I took on Project S2000. Lots of grip, lots of brakes, quick-reacting suspension with slop eliminated, more cooling, and more power. And be able to withstand serious track use.” As the car sits, I’ve done all of the mods I felt were necessary to get it to this state of being a great dual-purpose street and track car. It’s about 360 crank hp on 91 octane gasoline making it respectfully quick and it pulls all the way to redline instead of dying off. In 60F (15C) ambient temps, at the track, the oil didn’t go over 107C and the coolant stayed around 83C-85C with the help of the third radiator installation and GT3 front bumper vent. The AP Racing brakes with DS2500 street pads can take all of the abuse I can throw at them. The handling is sharp and responsive with the E-Motion parts, but still compliant for everyday street use with the help of the active suspension and DSC tuning; plus, my tires will last much longer. I love that I can go between street soft and track stiff at the push of a button. I use the button often on the street as I encounter rough and smooth sections of road. I also go stiff when encountering steep driveways to reduce the suspension compression to minimize scraping. Compared to the car being bone stock, I lapped Streets of Willow about 4 seconds a lap faster. On top of that, the car can now do lap after lap whereas the stock car would have overheated the tires and brakes. This car can do what the S2000 couldn’t and that’s being streetable with good power and hold up to track use; the S2000 could do two out of the three. The Cayman gets better fuel economy too as the S2000 would be hard pressed to get close to 30mpg on the highway.
Am I done modding the Cayman? Nope! But there’s nothing pressing to do as the car can do everything I ask of it as it sits. There is a little bad influence sitting on one shoulder saying to go with Tractive coilovers which have adjustable dampers compatible with the DSC. I’d target 70 N/mm front and 80 N/mm rear spring rates which I think would still be somewhat street friendly with tuning of the DSC. These are the spring rates used in the Ohlins R&T setup for the 718. But… I’d risk ruining the ride on the 405. For reference, a GT4 is 45/80 and the GT4RS is 100/160. Somewhere down the road, I’ll do some more mods to cut weight and improve feel. A pie in the sky modification would be the shorter gearing set from DeMan; it shortens 2nd through 5th gears approximately 10%. More power and response never hurts either and there are a number of ways to get there. So, I guess I have twelve years to get this project to its ultimate final state going by the S2000 timeline.
Edit: Here are some more pictures for gts944 of the rear control arm bushing to the factory rear tension arm. You can see the rear bushing is thinner than the bushing used in the front control arms.
11 comments
Great update. Any plans to go to a dedicated DOT-at wheel/tire set up for the track?
I’m planning on 19″ wheels and RE-71s (245/275 vs current 235/265) after I wear out these tires. Save a little mass. With the stock springs, I don’t think they can handle that much more grip.
The rear toe arms on your car are the non-GT4 Tarett ones. They’re just a different length than the GT4 ones due to different subframe and hubs. Your front tie rods look like Emotion, slightly different design.
Just did a very similar setup on my T with Dundon front tension arms (shims as well) and Tarett control arms. Curious how Emotion got the factory rear tension arms to work the their puck, which only has a center hole. I had to use the eccentric hole due to the factory tension arm not having enough machined off the LCA mount to avoid interfering with the edge of the puck in the center position. Wonder if they just machined it further out to fit. Trying to avoid either throwing off the toe curve with the eccentric or losing the T brake duct by going to an aftermarket rear tension arms.
Also didnt realize that the narrow 991 GT3 style LCA inners worked on our cars.
Cheers – always enjoy hearing about your project
I added some pictures for you and the parts list for the car. The front tie rods are E-motion parts. They don’t make their own rear toe links because there’s no real reason too with the various options already available. I had bought TPC rear toe links for the 718 Cayman, but they didn’t fit as the E-motion setup required GT4 compatible parts. So E-motion ordered up what I believe are the Tarrett parts.
Thanks so much for the photos! Finally got the car back together (didn’t realize that all the subframe bolts for the front sway bar were torque to yield, so took a bit to get new ones).
Seeing the sharpie mark on your trailing arm really helped. That was marking how far out they had to remove material from the inside of the flange, which was machined for the narrow metal interface on the rubber bushing vs the full width on the aftermarket solid pucks. Took a Dremel with a fine sanding bit and got a pretty nice result.
I had the pleasure of driving Khiem’s 718 at Streets of Willow CW (thanks Khiem!). Although I have limited seat time in Porsches, I agree with his comments on it being a well balanced setup for both track and street use. I’m excited to see the ride difference with the E-Motion Engineering spherical bearings and links installed! Any plans on increasing spring or roll bar stiffness? Looking forward to another track day soon!
Maybe coilovers…..
Hi Khiem,
Curious if you are considering upgraded Anti-Sway bars for this project or not. I have a GTS that came with single hole non adjustable bars and considering a second hand set from a GT4 that have three holes so I can adjust the bias front or rear. Still working on how thick my current ones are vs the GT4 bar.
Good job on the project so far, I love the tech and reading all of the articles. Looking forward to the next installment
Jeremy
I’m content with factory bars. I would typically use adjustable bars to tweak the handling balance, but I can do that effectively with the DSC.
Update: on my GTS I have now installed a set of used GT4 swaybars.
On the track I used to have to wait for the car to take a set into the corner, now it can just turn.
Still playing with the multiple holes of adjustment and feeling how the balance changes front to rear.
The front for our non GT4 cars require a shorter end link, the rears links work as they are.
I also have the DSC but don’t yet know how to go about making these changes as the DSC is based on velocity tables.
Thanks for the update! You can adjust the low speed rebound settings in the DSC to tweak the handling balance.
Agree on the stock suspension, especially in normal mode, needing to wait for the car to take a set. This is really evident in a slalom. I’m content enough with my DSC tuning for sport mode in that regard.