There is precisely a ‘ton’ of pad left on the fronts.
The rear pads are a smidge thinner than the fronts using my eyeball calipers.
The first iteration tune for the new turbo and 91 octane gasoline, Alex had the boost turned down to establish a safe baseline. For the track day, the second tune iteration had the boost turned up a notch. I had driven it on the street prior and it was a little knocky relative to my final tune for the stock turbo on 93 octane. On track with a lot more heat soak and high intake air temperatures, there was a fair amount more timing correction; that’s the difference between street use and track use. It was still a magnitude less timing correction compared to the car being completely stock from the factory and running 91 octane.
The weakest system on the 718 Cayman turbo 4-banger setup is the low-temperature coolant circuit for the air-to-water intercooler. The ambient air temperature during the first session was probably around 45F-50F. Being the first session out on a cold track, I worked up my pace slowly and you can see that in the gradual increase of the intake air temperatures. Once going full-speed, the IATs were around 60F-70F above ambient. I haven’t observed this myself, but I’ve read that the car starts to derate once IATs go over 135F. On the street, IATs are typically only 10F-20F above ambient. The GT4 side scoops help ram more air through the low-temperature circuit radiators, but something else needs to be done to significantly bring down the IATs for track use without derate.
The Porsche ECU has a PID controller for adjusting the wastegate setting in order to hit the target torque. Here you can see during the spool-up phase, the Wastegate Duty Proportional value is jacked up. As the torque increases and gets closer to the target torque, the proportional value decreases until eventually the torque target is hit and the proportional value goes to zero. The relatively fancy PID controller is in contrast to the basic look-up table in my Hondata KPro from the 2000s.
I’m currently on the fourth iteration of the tune for 91 octane. This plot shows absolute pressure, so, the gauge boost pressure is the absolute value minus atmospheric pressure (~14.7 psi). Alex reduced the boost a bit in the mid-range as it was a bit knocky there, but increased the boost up top. The Base tune is the ‘stock’ Stage 0 map in the COBB, but I had my 93-octane mix in the tank. The Protune Alex made for the stock turbo on 93 octane ripped. You can see the difference in boost level compared to the Base tune. Here you can see the RENNEN comes in about 500 rpm later than the stock turbo. That’s the compromise going with a bigger turbo; but running 91 octane compared to 93 octane is also worth a couple hundred rpm of spool. With 91 octane, boost with the RENNEN is limited in the mid-range to a bit less than 93 octane, but the RENNEN is pushing more boost at redline. Compared to the Protune on 93 octane, the RENNEN on 91 octane was still able to push 3 psi more boost at redline. If I used 93 octane, I bet the RENNEN could operate at 24psi across the board instead of only 21-22psi at redline.
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.