> This is the first good data and muffler design
 > information we have had so far.
 > The peak db readings are correlating well with
 > what we are seeing with the Mazda.
 > A 20 db drop in noise is an excellent result.
 >
 > If this muffler were 9 inches in diameter
 > and about 12 inches long it would have 800 cubic
 > inches. A slight variation would be 8.5 inches
 > in diameter and 14 inches long. Both should fit
 > in most cowls. OMC blasted air at the exhaust
 > pipes coming out of the engine with the main cooling
 > blower to keep them cool. A blast tube or electric fan
 > could be used instead.
 > --
 > Paul Lamar ...No rotor no motor.

Paul,
  Thanks.  A couple of questions:
   - Are the dimensions you've suggested empirical, or based on analysis
of the size of the OMC muffler?
   - Chamber sizes, locations of dual pipes from engine, and location
and sizes of pass-through orifices between the chambers:  Do we believe
that these things are critical, or can we get fairly good results based
on "TLAR" ("That Looks About Right") and the diagram?
   -  Cooling:  Maybe use the airflow from a fan behind the water/gycol
or oil cooler.  At the high temps of the exhaust pipes, the delta T
won't be much different if we use ambient air or something 50 F degrees
warmer.  Maybe this is an opportunity to also fit a tube to gather
cockpit heat (for those of us not living in the sunbelt).  The trick is
to get it all squeezed under the cowl in a way that also permits easy
inspection and service.

Mark W.

They are derivatives the 800 cubic inches OMC specified for the can.
The input pipes can be about 2 inches in diameter. As a guess I would
make the dual output pipes around 1.5 to 1.75 OD. One could scale
things off this dwg.

Paul Lamar ...No rotor no motor.

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