I am building a Lotus Super 7 clone which will run a 1982 stock 12a and a Weber 48IDA. I'm starting with a stock port motor until the chassis gets sorted then likely go with a Streetport or Bridgeport motor. My question is the exhaust. SCCA is requiring me to limit my sound measurements to 95db at 50ft and we all know rotarys are a bit loud. I intend to build my own header which should be fairly straightforward side discharge 2" primaries to a RB prefab 2" collector. After that I'm not sure where to go with muffler, presilencer, etc. I should have about 36-40 inches left for my side pipe exhaust system after the collector without doubling back on anything. Suggestions on a reasonably quiet (for race car) straight-through muffler system.



...mark

 

Get a Mazda Factory Race Lava Rock muffler, it's the only way to go. Make an account on the Mazdaspeed Motorsports website so you can have access to ordering one.

 

http://www.racingbeat.com/RX7-1986-1...ms/16425P.html



we used to run that into a 6" diameter x 16ish inch long x 3" inlet/outlet dynomax for mid 90's DB.



on the stock port engine 2.5" pipe is fine for power and better for noise.



on the bigger port engines the INTAKE noise becomes loud too, so any kind of airbox/filter setup will help