Hello Guys,

    In regards to exhaust tuning the current conversation seems relative to
straight through exhaust systems which are good for speed and low
back-pressure, but they're not historically good for really quieting an
engine.  Baffled systems like those used on automobiles are extremely
efficient at stopping noise, but does anyone really know what the price for
quiet is in terms of power and performance.  A third possibility no one has
spoken of is straight through sequential baffling similar to a gun silencer.
    With all the engineers out there somebody has got to know somebody that
has real world expertise in this area.  We all know what they do on the race
track where performance is the ONLY consideration, but when the race is over
and you walk back to your car and turn the key you don't want to hear more
of what you left when the checkered flag fell.
    A luxury road car and a cross country airplane have a lot of necessities
in common, all of which relate to comfort.  --  And a loud exhaust system is
NOT on the list.  My personal project is a long range cruiser powered by a
20B and I'd like it to be a quiet airplane.  Unfortunately I may have to
experiment with a lot of different exhaust systems to find the best of both
worlds unless you guys can help me out.  There are some very respectable
high performance sports cars out there with relatively quiet exhaust
systems.  The question is "Can they be made small and light enough with the
efficiency needed for an airplane?"
    If anyone knows an engineer with R&D in this area, please put him on the
keyboard.

Thanks,
Robin

All this talk of mufflers sounds like it is a big problem but it is
not. Mainly it is making something that works that is not too heavy
and will last for 2000 hours.

Come on down to Tracy's flyin next year or buzz on down to Bell Florida
now and get a ride. His airplane is quieter than most airplanes. 
Stand along side the runway when he takes off and  listen.
I think you will find it is quieter than most. His muffler failed 
at a thousand hours because he used some O-too-thin material.
Perhaps Chuck Dunlap will also give you a ride if you prefer Phoenix AZ
to Florida. Chuck's airplane is also quieter than my C182.

If you are in the St Louis area Tom Jordan has a supercharged 13B
extra Long EZ that you may get a ride in or be able to listen too.

BTW Bill Freeman, have you talked to Tom lately? Last I heard at OSH
he was getting it painted. Picture below.

Paul Lamar
 
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