Mike Wills wrote:

Lynn,

  Do you have a part number? Borla makes a lot of different styles of
mufflers. Some are claimed to be light weight others make no claim for
weight at all but appear to be very heavy. Which are you using?

Mike Wills

I don't know what the p/n is. It was about 24" long with a 3" tube.

Maybe 9

pounds.
Lynn E Hanover

Is that overall length Lynn or just the length of the muffler part?

IMHO you guys are going to find it hard to beat a simple tangential
muffler in terms of  noise reduction to weight ratio. Number one it

requires

no internal baffles or packing. The exhaust pulses just twirl around in

there

until they are homogenized.

Paul Lamar

After messing with several designs now I think Paul is right about the
tangential muffler.  I do agree with Jeff about the potential "vortex"
problem and I think I experienced a bit of that.  You should take his advice
on outlet placement if you go with this type.  I gained power with more
conventional mufflers but also noise.  The Edelbrock now installed is a
pretty good compromise but still not what I ultimately want.  I was doing
some critical evaluation flying yesterday.  When I leveled off at 5000 ft
and set cruise power I thought "this is perfect!"  Just a nice reassuring
background hum, not enought to bother me even while listening to classical
music.  Then I happened to swallow, my ears adjusted to the reduced pressure
at altitude, and the noise level went up about 3 DB.  Still not bad but my
mental "standard" had been set by the relative silence moments before.

I also do not like the esthetics of a conventional looking muffler hanging
under the plane, not to mention the drag.   (The glass pack I tried looked
good but was too loud)  I landed and formulated my next attempt which takes
the advice of a previous poster who said that there is no substitute for
cubic inches.  Something about this rang true with me so, to get everything
I want (low noise, low weight, muffler out of cowl, low drag and estheticly
pleasing) the next muffler will be a 4 - 5 foot long 4" diameter pipe (5"
was too expensive) under the fuselage.  I'll try baffles at end of this pipe
first and then many small widely spaced holes in the pipe.  Finn flew his
version of the "holey muffler" here last Saturday but I think his holes were
too large and too closely spaced to give a good idea of how well this may
work.   It is glorious to see other rotary powered planes arrive and take
off here at Shady Bend Airpark though!

Tracy Crook
rws@altavista.net
www.rotaryaviation.com

 
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