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

Borla make a selection of stainless straight through mufflers in different
shapes and lengths. We ran a oval shaped 3" for a year and for 2000 ran a 4"
round. Both gave us under 98 DB at full throttle 50 feet from the car with a
bridge ported 12A. 

Lynn E. Hanover

What was the lenght of the pipes before the muffler Lynn? I ask because I am
trying to judge the temp they were running at. Also what did the 3 inch
oval muffler weigh?

Paul Lamar


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