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

I bought a used exhaust tailpipe off a base Cayman for cheap so that I could take measurements and design my own x-pipe exit. I designed it so that it can be fabricated from straight 304L SS in 2.5” OD size. I bought three feet of straight tubing from Burns Stainless for about $100. I made a design using mandrel bent tubing too, but the cost of the raw material goes way up for the mandrel bends. I recall material costs would have jump up to $300 or so. Will my design reduce some exhaust back pressure? I think so. Do I expect significant gains? Not really, but it makes me feel better. It may help with the whole lack of 93 octane situation. I have some other stuff planned for the rear of the car to give it a more GT3 Clubsport feel too. Even with the car in Sport Plus mode all the time keeping the exhaust valve open, the exhaust is relatively tame; I think it is quieter than most BMW M cars. I do not think my X-pipe will increase the loudness, but it should change the tone.

Why am I running the car in Sport Plus all the time? I have a theory regarding the common water pump failures on the 991.2 911s and the 718s. In the name of reducing emissions, recent Porsches come with this switched coolant pump. After the engine is started, vacuum is applied to the water pump to actuate a shutter to stop coolant flow which allows the engine to rapidly warm up. The quicker the engine reaches operating temperature, the lower the fuel consumption and emissions. However, this switched coolant pump is also a very common failure point. The seals in the pump fail and coolant leaks out along with getting sucked into the vacuum system. If you recall, Normal mode keeps the coolant temperature around 220degF whereas Sport brings the temperature down to about 184degF. Typical rubber seals degrade faster with higher temperatures. I was originally planning to just plug the vacuum line to the pump so that the shutter would never be actuated, but I have a single data point of a 991.2 owner still on his original pump after almost 50k miles and he drives almost exclusively in Sport mode. Some owners have had their water pumps leak in as little as 3k miles. I do like the engine warming up faster because that means I can get on the throttle sooner. But I do not want to degrade the seals in the pump so that they lead to a failure. I guess we will have to check back in 5-10 years and see if this strategy has worked.

Bandit likes the deep bolsters of the full bucket seats. The deep side bolsters gives him a place to lean his butt up against something. Molly is quite happy with the extra floor space. The Cayman is rather spacey with all the storage space and relatively larger interior. In the S2000, I had the driver’s seat adjusted most of the way back. In the Cayman, I have the seat adjusted most of the way forward. I am 5’10” for reference. The Cayman has a wheelbase ~3″ longer and it seems it all went into leg space which makes Molly happy; she would not have fit comfortably on the floor of the S2000. The seat cover is from 4Knines if you were wondering and I did place a towel in the seat to reduce the bucket depth to improve the seat cover fitment.

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. I guess it will be my Cayman version to what the GT3 Touring is to the 911 lineup? Project S2000 could tackle any track in any weather when it was naturally aspirated, but not after it went turbo. The foundation of the Cayman is already suited to higher power with bigger base brakes and more airflow opening area for cooling. It helps that Porsche has track-worthy 400+hp GT4s in the stable on the same platform with similar bodywork. The GT4RS is a whole different level with regards to the bodywork, aero, and thermal management in order to manage 500hp. Project S2000 is way faster in a straight line than the T having about 30% more power and 7% less weight. I do not know if I will get the Cayman T to match the acceleration of Project S2000, but I will try. But, um, it may take me a while.



    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 🙂

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