Muffler on run stand: 3,000 cc Corvair

Builders,

Project of the morning was going to the scrap stainless tubing bin and buying a $29 muffler for the test stand. I want to make the runs at Corvair College #39 quieter, so they do no interrupt ‘Classroom discussion’ at the College. Below is a sound sample of the same engine as yesterday, a 3,000 cc engine built for a Zenith 650.

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Above, the 2 into one Turbo muffler exhaust system. In the last 40 years hot rodders have purchased a zillion ‘Turbo’ mufflers, and 98% of then never knew the origins of the design are Turbocharged Corvairs. This particular one is a Thrush, made in the USA…..Now wait for it……Yes the made in China one cost $4 more.  I would like someone to explain to me how that can be blamed on excessive blue collar American wages.

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Above, 13 second sound sample, same RPM , same motor, (3,000cc Corvair for Zenith 650)  nearly identical atmospheric conditions one day apart. The loss of peak rpm on the stand was negligible, and possibly more the fault of a 10F temp increase. Because of the cam profile we use in Corvairs, they are not harmed by a muffler, but nor do the respond to “tuned” exhaust. The Exhaust systems we sell are a common sense system that balances reasonably good flow with low weight and surface area. The test stand runs stock Corvair cast iron exhaust ‘logs’ for ease of rapid engine changes, but we don’t fly them

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Above, same engine running. My manual has more information on mufflers more appropriate for flight, we used one on my Pietenpol for years. His set up is about as quiet, and builders who attend the College will be able to judge is a muffler is something they wish to add to their aircraft.

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-wewjr.

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