Project Cayman T: Part 1 – Intro and Must-Do Mods

On the 718/982 generation Cayman, the outer scoop panel snaps into the inner two-opening panel and the whole thing snaps into the side panel of the car. There is some debate currently on the forums if the 3 screws from the 981 generation Cayman are still necessary to securely attach the scoop to the side panel; to use the screws requires removing the side panel from the car also and that is a bit of a pain in the ass. People have observed the trailing edge of the scoop separating a bit from the side panel during high-speed track use, so the scoops are definitely working.

I am going to wait until the engine is fully broken-in and I have a datalogging solution before I install the GT4 side scoops. I plan to try to quantify their effect on cooling performance. This is really important on the 718s with the turbo engines. The turbo engine uses an air-to-water intercooler and the two radiators for the coolant are located in the two side openings. It is well-documented that the 718 runs high intake air temperatures on track. Once the IAT reaches a high enough temperature, which is not that high, the ECU pulls back power. Anything to cram more air through the radiators should help. The air intake for the turbo grabs air from the left side scoop also, so anything to try to get some ram air.

In the pile of Radiator Grill Store parts, you may have noticed the grill for the large center front bumper opening too. At 300hp, the coolant and oil temperatures are managed well on-track. But at 400hp, not so much. Porsche has a third coolant radiator that gets installed in the front on the higher performance trim 718s and also for hot climate markets. I have ideas dancing in my head of adding a third radiator for the intercooler coolant loop too to help keep IATs down. I have years to work on this, so we shall see.

I have a few hundred miles on the car now breaking-in the engine. It seemed to loosen up after about 150 miles which I felt as less engine breaking. When I broke in the built engine on the S2000 on the dyno, that took roughly 25 miles. Initial impressions: the bucket seats let you know right away it is not some regular car. The shifter and clutch are higher effort than the S2000, so it is not like you can just be super relaxed. You have to put in focus. The stock tires are Pirelli P-Zeros which are 220A treadwear rating. I have only taken a few corners at elevated speed, but these tires do have solid grip. The overall grip level is about the same as Project S2000, but the suspension is quite squishy, relatively speaking. Quick slalom transients have a lot of body roll (relatively….) and you have to wait for the car to take a set. I do like the active suspension. I drive most of the time in Sport Plus which is stiffest, but a quick turn of the dial to Individual mode softens the suspension up for pot holes. The car is actually very comfy and quite quiet even with the PSE. It will get 30mpg on the highway easily too. Lane Change Assist, I am very glad I got it. There is a huge blind spot looking over your right shoulder due to the fat C-pillar. The BOSE stereo is just okay, but it does have some decent bass, bass that most ‘base’ stereos do not have. So I do not have an immediate urge to upgrade the stereo. The fire extinguisher, I hope I never have to use it, but you never knew when someone else may need the help. About the auto-rev matching, I thought I would not like it, but I actually do like it quite a bit! If I am just cruising, I still double-clutch my downshifts. But if I am hustling, I just let the auto-rev match do its thing.


Back to the exhaust. With the Sport Exhaust that is standard on the T, there is a valve that closes off the flow path to the right-side muffler which forces all the flow through the left-side muffler; this diagram does not show the valve, but it mentions the valve on component 5. The lower pipe connecting the two mufflers causes the right-side muffler to act like a big resonator to bring down the volume when the valve is closed. When the valve is open, the two exhaust flows go straight through both mufflers and run into each other head-on in the exhaust tailpipe. Then the exhaust has to make sharp 90 degree turns to exit to atmosphere. I really dislike the fact the flows from the two mufflers ram straight into each other and then make sharp right angle turns.

One interesting thing is the cross-over tube between the two exit pipes. A mod some people like to do to increase noise is slide that bottom coupler joining the two mufflers to create an exhaust leak. It is a cheap loud mod for those wanting to increase noise. I do not want to increase noise.


    1. I auto-x’d a C6 when it first came out way back when. I didn’t care for it; it felt bigger than it was whereas the Cayman feels smaller.

      1. I hear you. I cycled through an AP2 S2000, C6 Z06, F80 M3, and now TTRS daily and 991.1 GT3 track car. between these cars and rentals and driving friends’ cars, realized I valued a smaller lighter car and mid/ rear engine feel over other factors. There’s always someone richer/ smarter/ faster, go the route that makes you happy.

    2. Except Khiem has a car he can drive to and from the track comfortably and also drive on a daily basis. A Cayman is far more comfortable than a C6 on a day to day basis. More interior and trunk space as well. Plus he doesn’t have to put up with a god awful early 2000s GM interior.

      More money, but you get what you pay for.

  1. I have solid trans mounts in my base 718. I think I bought the 981 models from tarett engineering. With the standard mounts a floor jack under the back end of the trans could move it 1.75 inches before the car moved. That was with 20k miles. Didn’t notice much change in nvh. Improved shifting a lot.

    1. Good to know on the compatibility! I was hoping Porsche would carry over parts as OEMs do to save money. I still need to figure out how to disable any potential error codes because of the active mounts. I hopefully can code out the active mounts as they are an optional feature.

    1. It’s a digital tach. But at least one of the display options is round like an analog tach. Other options include a bar…. graph, I guess you could call it. Which I did not particularly care for on the S2000.

  2. Thank you for the explanations of how the switched water pump works to reduce temp in sport mode! I do have the same idea of leaving it open all the time for cooler operations. I like the idea of plugging the control vacuum line. Do you know where that pump is? I have a 23′ CGTS 4.0. It has the same enhanced cooling feature, and I’d think it has the similar cooling components. Thanks!

    1. I don’t know where it is on the 4.0L 6-cyl, but on the 4-cyl turbo, it’s on the side of the engine next to the passenger compartment bulkhead. I’ve found pictures of where the vacuum line goes and it’s not easy to get to.

      For now, I’m content with just running the car in Sport + mode all of the time. I need to ask someone to see if the water pump still stays closed for faster warm-up from a cold-start even in Sport + mode. I imagine it would in order to reduce emissions. In Sport +, even during track use, I only saw the coolant temp get up to 87C max. I’ll see it fluctuate between 82-86C during everyday driving.

      EPDM rubber is very commonly used in cars for gaskets, o-rings, and coolant tubes. Anything related to the coolant system, EPDM is typical. It commonly comes in two grades, cheaper that is good for 120C and more expensive that is good for 150C. Having worked for a long time in the auto industry and also observing the frequency of water pump failures on modern Porsches, I have it a very high likelyhood the cheaper rubber is used in the water pump. I mean, there’s even a plastic impeller instead of metal. OEMs are looking to save a dollar anywhere they can.

      In Normal mode, it seems the coolant runs between 100-105C. Which is a lot closer to that 120C limit. So my hypothesis is running in Normal degrades the seals and gaskets in the water pump much faster. Plus the engine runs much warmer oil. So after a drive and doing a shutdown, everything is just going to be hotter. But running in Sport + with the coolant only around 85C and oil around 90-95C, the seals should last much longer. Fingers crossed.

  3. Thanks again for sharing your knowledge! I’d think the thermostat should take care of the faster warming up mostly, as it opens up typically at 180-195F (not sure about Porsche cars)? The open water pump will circulate the coolant continuously, but might not affect the oil warm-up much…at least, that’s my theory :).
    Aside from the vacuum controlled water pump you mentioned, there looks to be a vacuum control valve for the coolant going into the engine oil cooler. I don’t know how to add picture here, but if you google ‘718 BOXSTER ENGINE OIL COOLER INLET LINE OEM 98130707500’, you will likely find used parts that show the picture. It looks to be controlling the amount of coolant, or maybe just on/off, going into the engine oil/water exchanger (located on top of the engine, driver side, by the oil filter in the 4.0L)
    I’ll make a spring project to play with vacuum lines and see what happens 🙂

Leave a Reply

Your email address will not be published. Required fields are marked *