Ed Anderson wrote:

  At least on my installation there are two things that are less than ideal.
I had not yet installed any uphostery and the vibration of the engine is
transmitted through to the fuselage.  I should have taken more care (rubber
exhaust dounts perhaps?) to insulate the fuselage from the viberation.  With
the Rv-6 being a tin can and without any uphostery it can at times get
noisy.

Ed, you might want to consider a round muffler made out of Inconel (or heavt
SS)fed by both exhaust pipes with an exit pipe facing away from the fuselage.
These systems are quiet and more efficient, plus you'll never have to replace
it. Individual pipes are not efficient, and they are the nosiest type of
exhaust, especially if they are close to the fuselage and parallel.  Dave Atkins
makes 170+ hp and it's quiet. Paul has some drawings for round mufflers, as
well.

If you've hard mounted your exhaust system to the fuselage that's a big no-no
because it can lead to fatigue failures because the engine is transmitting the
vibrations thru the exhaust pipes to the fuselage. If the system is built well
you won't need a hard mount, or if necessary, brace it back to the engine.

Chuck Harbert.

Allan Tolle in the Power Sport RV4 went 138 MPH in the Sun & Fun 100 mile race 
with two long pipes and they were not that noisy as I recall. I like Finn's
idea of opening up the front of the large concentric tube to cool the guts
of the muffler. Should allow a lighter weight muffler.

Paul Lamar

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