Carpokes

I’m looking for track experienced drivers to weigh in. I just bought a Cayman GT4.0 with LWBS, PDK, and PASM (20mm), primarily so I can drive to and from tracks on for the next few years. I also own a Boxster 25 use it occasionally for some touring purposes (similar car but different purpose). I’m new to Porsche platform but skilled with plenty of track days behind me (currently drive a track built S2000). My goal is to setup the GTS4.0 for HPDE track days and yet retain some street drivability. Unlike the S2000, I understand the Cayman has some limitations on alignment and setup in OEM form. I’ve researched the net and reached out to several performance shops/retailers to get opinions on the following. All of them offer contradictory opinions. Thought I would get knowledgeable answers from this forum and learn how best to approach my goals and mistakes to avoid given my lack of experience with Porsche platform. In the end I want to walk into my local performance race shop armed with good information to compare against their recommendations.

After break-in and some seat time in stock form, I would like to modify stock components for improved safety, braking, and handling while enjoying the car off the track. The intent is to improve safety and performance while on track and not build a GT4/RS replica. I’ve run a non-aero track setup for years so it will a “sleeper” type build that slides under the radar to the eyes of many. Here the list I have so far.

Safety: Half-cage/roll bar with 6pt harness, SS brake lines, seat angle adjuster for proper helmet position
Brakes: wheels studs w/ track pads and rotors
Wheels: Apex 18”
Tires: 200 tread wear in 245/285 f/r specs
Desired alignment: -2.5/-2.0 with 8.5 caster and some rear toe
Suspension: front LCAs/camber plates, rear toe arms, strut tower steel plates
Exhaust: headers, OAP, back box setup w/ tune

I’m keeping OEM shocks and springs for now. May move to Tractive shock body and DSC tune if needed while maintaining the PASM function. Please reply with your thoughts on the following.

1. LCAs or Camber plates or both? Tarret, Elephant Racing or Rennline experience?
2. Strut tower reinforcement needed? Cup plates or Emotion Engineering strut brace?
3. Recommendations of a brake pad compound friendly for HPDE and drive to and from track days.
4. Are stiffer springs a must out of the box?
5. Should I consider tractive/DSC sooner than later?
6. Quality SS brake line recommendations?
7. CMS/BBI/Cantrell half-cage/roll bar experience?
8. Anything else to consider with this platform?

Thank you for your knowledge and responses - PMs welcome as well.

Your Cayman GTS sounds like my 24, as I have a PDK and LWBS also, though I did not get the 20mm system for a bit more height. At present I only have 2.25 degrees near negative camber up front , but I ran 255/18 Hoosiers up front and 295/18s in the rear with not problem. In back I have a set of Tarett toe link struts with camber set at -1.9 and Winter will bring an install of GT3 A arms and shims from Rennline ---- would love to go 265 up front with either 18s or 19s, and possibly 305s in the rear. I do have 2 sets of Apex wheels ( one in 19s and another in 18s ) and I highly recommend these for track use with one caveat, the knurled edges are no longer being done with the flow formed models , so do spend a bit more and get the Forged Apexes.
I commend you for putting in a frame bar or partial roll cage system as those are on my list also. The car is a solid Time Trial machine but do follow NASA or Regional Rules carefully as you want to stay in TT3. You will enjoy the Cayman and having owned a S2000 years back you may find some similarities at high speed corners.
With folks running Caymans in autocrosses and on road courses chat with folks for your primary goal. I am hoping to get around -2.8 to -3.0 degrees negative up front , but some autocrossers really push for -3.5 or more. I will be happy with -2.8 up front as I was getting decent wear even at my current setting...........and I am aggressive.

Welcome and glad to have another RennRatte on Das AutoPoke Forum, ha!

Thanks for responding Willy asap. Nice to hear that you also had an S2000. Assume you have Tarret camber plates right now up front with that degree of negative camber. Definitely getting forged wheels. I have Titans for my S2000 and Apex wheels for the M2Comp. They have held up well n track duty. But I will move forward with Apex as I like their replacement deal or a wheel gets damaged. My dedicated track car has -3.4/-3.0 camber so I’m going keep the Cayman dialed in below that for tire wear purposes. I’m not much into AutoX but may try some more seat time given my access to tracks. Assume you drive to and from tracks. Thigh I would start with some basic specs and dial up if needed. I might even try -2.2/-1.8 first….just enough to get rid of some understeer and have the car rotate a bit better.

Have you experienced any concerns with the strut tower? I’ve been reading that some 991/981/718 owners have seen cracks or outright damage under track conditions given the change to high-cast aluminum strut towers. What pads are you using? Post up some pics of your GTS. PM me if you want.

There's good input regarding some of your questions scattered about Carpokes but the post are not always quickly found. I'll try to find some of what a few of us here have shared.

Meanwhile as a start, here are upgrades/changes done to my 2021 GT4 which mostly lives on track. A copy of current alignment too.

@blueline thanks for all the great information. Very helpful, even for GTS trim. Some of your items I have on my build list as well (eg., Ed Guard items, Suncoast panels, etc.).

Few questions from your build.

1. Did you have to cut panels to get the Cantrell half-cage to work?
2. Reason why you have square alignment? Assume sway bars are adjusted to full stiff upfront.
3. How does the car feel and sound from the full M tune? Sid you tune throttle and delete the on/off/on valve feature as well? I’m actually going with full Kline setup.
4. Does the DSC setup really work well? If so what do find it does for the car on track?
5. Any failure issues on track on anything?
6. Something you did that you won’t do again?

Thanks for listing this out and getting me links.

I haven't forgotten your questions Sam. Will get you some answers in a bit - I'm buried at the moment! (Well, not literally. Lol.)

blueline wrote: Wed Jan 08, 2025 8:49 am I haven't forgotten your questions Sam. Will get you some answers in a bit - I'm buried at the moment! (Well, not literally. Lol.)

No rush on my end. Thank you.

Sam_Flat6 wrote: Tue Jan 07, 2025 8:47 pm @blueline thanks for all the great information. Very helpful, even for GTS trim. Some of your items I have on my build list as well (eg., Ed Guard items, Suncoast panels, etc.).

Few questions from your build.

1. Did you have to cut panels to get the Cantrell half-cage to work?
2. Reason why you have square alignment? Assume sway bars are adjusted to full stiff upfront.
3. How does the car feel and sound from the full M tune? Sid you tune throttle and delete the on/off/on valve feature as well? I’m actually going with full Kline setup.
4. Does the DSC setup really work well? If so what do find it does for the car on track?
5. Any failure issues on track on anything?
6. Something you did that you won’t do again?

Thanks for listing this out and getting me links.

Some answers. Before I start, note that some of the upgrades were done 4-years ago, while other changes followed within the first year or so. The Cantrell roll cage, Schroth 6-pts, etc. were done before I took delivery of the GT4, a retail order specifically meant to be a replacement for a dedicated track car that I had sold earlier. I pre-planned and had those initial items purchased and ready to install before the car ever made it from the factory to the Porsche dealer. When I drove it home from the dealer it had 20 miles on the odometer with those items already installed. It was great!

1. Yes, interior panels were cut but they were done by someone very skilled. The installation is professionally done and looks great. I've had compliments on the installation. Looks factory!

2. Square alignment works wonderfully for the GT4 - and most especially for me. Yes, Club Sports in sanctioned racing will generally have say, -3.5 front and - 2.5 rear, at least as a starting point, but for a regular GT4, symmetrical is good. As proof, the car does what I ask it to do. Square might not be the case for others but it works for me.

The specs were suggested to me by one of the best in the sports car racing business, Andy Pilgrim who knows my car well. (He's driven it.) Andy consults on setups (and tires) for various race teams worldwide in addition to his continued storied career as a fantastic pro race car driver, still in great demand. Here's what he suggested: "As far as the camber I would make it as square as possible right now. You will pretty much always end up with an understeering Cayman GT4 as you have so much weight at the back (Same with our Cayman GT4 race cars) but squaring it off will help keep the back stable to start with and you can adjust from there."

Well, I've kept the alignment square except for increasing overall camber all around as I added the new Tarett parts. I like the way it performs.

Andy also stressed toe settings. Where mine are as shown in the alignment sheet is where they should be, at least for my setup.

I was also having terrible tire wear the first season. Correcting the camber (among other things such as going to the Apex 19" forged wheels) rectified that.

As for the sways, front Full Soft and rear Full Stiff. This what most race shops recommend. Also it's what TPC Racing/DSC recommends for the GT4. (Andy P too.)

3. I like the M Engineering tune although I really didn't have much HP to gain over stock since the GT4 is already very well optimized in that respect over a GTS. You will get a considerably more additional power from stock with your GTS should you go with a tune. I discussed everything with the fellows at M Engineering and they took it from there and sent me their tune interpretation which I then uploaded/flashed to the ECU via a laptop. How much did it help? Well, the response is a bit quicker I think and it seems "livelier". (Whatever that means. Lol.) Can't say that my lap times are better but that might just be circumstantial or the driver.

PSE is either on or off based on what I choose with the console switch, which is what I specified to M Engineering that I wanted. Not related to anything, but I did a Sound Symposer delete - I didn't want too much drone. That probably was unnecessary however - at first I kind of missed the extra little bit of piped in exhaust note. Hah.

4. DSC - that's a tough one for me. Yes it works but I can't really describe the difference. It just feels right. Maybe it's all in my head, but in any case, I'd need to do immediate back-to-back comparisons which would require a lot of USB to laptop connections while at the track. Too tedious and time consuming as I prefer to just get in the car and go! I did talk to the folks at DSC a bit and we all decided that the setup they programmed would probably be fine. I've never changed it nor wanted to. A bit lazy I know, but I don't want to get into the weeds that deep, not knowing where I might be headed.

5. Failures so far are none. The engine might go before I do and if so, I'll strongly consider going with a DeMan 4.5. I think it would be pretty awesome. Lots of hard track driving will wear other parts beyond the usual brakes, tires, etc. but that's part of the trip.

6. The only issues I'm having at this time are heat related damages to some components in the rear (outboard CV joint and upper sway bar boots). They are misshapen and getting crispy. Also, the body seam sealer and undercoat is roasted in places from the heat. Alligator looking. I have Soul OAPs that were not installed until the end of the 2023 season and I think they are the culprits. The Jet-Hot has flaked off in places but I doubt that is sufficient to cause the damage we're now seeing. The Soul pipes don't have the double wall of the OEM versions and that may be the issue. Not sure if that's true and not sure what we're going to do but I may end up going back to the stock pipes. Also going to look into wrapping the Souls and/or trying to get more air to that hot rear area.

My advice is to watch the heat if you're doing aftermarket exhaust components AND if you're going to track the car. If you drive it hard, there will likely be heat damage and that will need to be figured out.

@J-Dub and I are both dealing with this heat issue. J-Dub is doing some experimenting and, since he lives in Phoenix where it's warm ( ), he was going to the track this past weekend. Hoping that he finds the cure!

@blueline thanks for all this information. Very helpful to better understand what’s worked and what hasn’t. I understand there are compromises that go along with modifying these cars for optimal track performance. I know you can’t have everything without some compromises. But hearing from a few folks on this forum helps me better understand where those might lie. Much appreciated.

Incidentally Phoenix area is mostly where much of track time exists given I lived there for 18 years. I still have two cars down there for this purpose alone.

Ole blueline and J-Dub were both super helpful to me on their set ups and I do envy that blue has a bit more camber range with the GT4. J-Dub is from Arizona so there is a good chance you two will meet!