Francois, When working with Mazda racing years ago they produced a "tuned exhaust" that worked very well. There was no trick to it, it was simply a shallow taper megaphone long enough to assure that multiple exhaust events (port openings) occurred in the desired power range, while allowing the exhaust to escape somewhere that wouldn't kill the driver. The megaphone exited a RX-2 near the hinge line on the passenger door. This was in the non muffled era of racing. I'm sure this car caused the need for muffling more than all other race cars combined. Wearing foam earplugs, AND ear muff type protection it still HURT to be near it! The length was approx 26" but Mazda said the length wasn't as critical as the flow restriction. You couldn't run this in your plane however as the noise would get you banned from all but military airfields and drive you to distraction. The rotary is not like a two stroke. It is a true four cycle, and as such needs scavenging with no reflected wave like a two stroke. Bill Jepson

 
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