Now that our turbo system is mounted, we started fabricating a 4” downpipe with recirculated wastegates and a 3.5” exhaust system for our FD RX-7 using SP Mufflers and Vibrant Performance mandrel bends, V-band clamps, and Bellows.
Rotary engines produce not only a lot of heat, but a lot of noise as well. Aggressive porting can make them even louder and since our 13B REW was bridge and semi-peripheral ported back in Part-13, finding a muffler that can durably handle the heat and effectively keep the decibels in check was important to keep this car well-rounded and enjoyable to drive.
After a bunch of research, we landed on SP Mufflers due to their vast experience making mufflers for rotary-powered cars, and because they produce some of the largest mufflers that can fit in an FD RX-7, which is fundamental in reducing sound.
SP Mufflers is based out of Sydney, Australia and makes high performance custom mufflers that are 100% made in-house from materials sourced from Australian suppliers in order to ensure performance and quality. SP Mufflers starts with sheets of 304 stainless steel that is cut and rolled/formed into the muffler bodies and end caps. Inner cores and insulation are then added before being finish-welded as a complete muffler by their talented fabricators.
We chose SP Muffler’s 3.5” FD RX-7 Cat-back Dumpy Muffler for the rear of our FD. This downward-turning exhaust tip design is often called “Dumpy”, “Dolphin Tip” or “Dolphin Tail”. This SP Muffler is called their 10×7” oval muffler that is 16” long, making it one of the largest available for the FD.
SP is a great company to deal with and because they specialize in custom mufflers, they were very flexible with accommodating our needs. Since we were fabricating our entire exhaust system, SP saved us a lot on shipping costs by selling us their FD muffler with just the factory hangers and exhaust tip. This greatly shortened the overall length of the shipping container.
To further suppress sound and reduce drone, we chose SP Muffler’s 3.5” FD RX-7 Resonator which they call their 8×5” oval muffler that is 13” long. This is also one of the largest mufflers that you can easily fit in the center of an FD RX-7 where the factory catalytic converter is positioned.
Between the 10x7x16” rear muffler and the 8x5x13” center resonator, we have 1,640sq-in of volume to absorb the sound waves from the exhaust gasses from our loud, ported rotary engine. We are very eager to see what the pitch of our exhaust note and overall volume turns out to be with this setup.
3 comments
Billy, the exhaust looks fantastic. Every update gets us close to the full reveal of this monster!
Thank you! I’m a bit behind on articles so there will be more updates that will come out soon. The car is close to firing up!
I see you’re also a glutton for punishment wrenching on cars while laying on our backs, ha! Excited to see this up and running with all the extensive and detailed work on it.