A couple hours of my time doing a few design iterations, a hundred dollar’s worth of 2.5” OD 304L SS 16g tubing from Burns Stainless, and paying a buddy for his fab time resulted in a new X-pipe. After comparing the 3D print again to the real Cayman exhaust tips, I extended the tips 40mm.
Most of the flow path in the merge is blocked off to the opposing flow.
I am really happy with how this turned out. My buddy does good work and also back purged all the welds. The cross section at the middle of the X is basically an ellipse with height of 2.5″ and width of 3″.
I used an angle grinder to cut in slits in the joints that will slip over the mating tubes in the stock exhaust. There needs to be some free play in order to slide the parts over each other and then the exhaust clamp tightens everything down.
After the shuffling back and forth with two jacks, blocks of wood, and jack stands during the first oil change, I bought a set of liftbars from liftbars.com. Imagine that. In order to get the car high enough to fit my jack with the liftbar under the car, I have to get the car up on a couple blocks of wood first.
4 comments
Some of the aftermarket companies (I think Soul?) were claiming no power gains on the 718 with a straight piped catback exhaust. Different X pipe tip design than yours though. Any thoughts?
Anything the baby 2.0 stock turbo can put out, not going to see much with the going cat back. Maybe on the bigger S or GTS turbos. Even then, not much gains to be had in the exhaust until turbo upgrade in my opinion. The only real bottleneck in the stock exhaust is the stock cat. Replacing that with a high flow sport cat is the best place to uncork restriction. Otherwise, the downpipe is huge and then that splits into the two approximately 2.5″ exhaust pipes that go to straight through mufflers. At the exhaust tip, text book loss coefficient for a 90deg bend is 1.1. A 45deg bend is 0.4. Mine is 60deg but I think gain benefit by not having the pulsating flows crash into each. Regardless, need a tune to take advantage of any potential flow improvement at higher power levels. Otherwise the stock ECU will just keep on hitting the programmed in torque target. Or if on crap fuel, better exhaust flow should mean less knock. But for sure, the stock cat is the major bottleneck. The other bottleneck is the small compressor inlet tube. Raggdoll Motorsport has a good upgrade for that.
Nice design. A little surprised you didn’t angle the cuts on the tips. Hopefully the crossflow design helps with scavenging. I imagine there’s a slight change in exhaust note.
I thought about the slash tip for about a minute. But it added two more cuts along with another area to add error and visually see any misalignment of the tubes. I figured flat cut was good enough for a GT3 racecar, good enough for me.