street here in LA. There is no doubt about it... NA P-port engines
are more affected by back pressure than side port engines. You just
have to choose your muffler more carefully.

George Lendich wrote:

If I could expand on Paul's very correct statement a little more - it
was
explained to me ( I had a good teacher) that the PP increases overlap
(
which we all now know) and because of that any restriction causing
backpressure in the exhaust will cause more exhaust to contaminate
the inlet
charge.

The rotary will self evacuate ( scavenge) the exhaust at higher RPM,
but
designs with possible restrictions have to be considered carefully.

So any muffler that doesn't cause backpressure because of restriction
is
perfectly OK. Any exhaust that can cause a vacuum ( at the end of the
exhaust pipe) would be a great idea!

The Devils in the detail !

George (down under)

   Thank you gentlemen, you made my day. Sounds like there is still
hope. Now, how long before you guys come up with a muffler that quiets
this beast and creates no back pressure :)))
   Thanks again,
    Randy

-- Kevin & Kim wrote:

Right.  I may be blowing a whole lot more than hot air here, but here's some
"out loud thinking."
A little overlap from my choir days at St. John's Cathedral in Denver.
How about this:  A tuned exhaust borrowing from a pipe organ.  Sound is
produced when laminar flow air flows through the foot of the pipe and some
flows out the mouth (the hole in the front of the pipe). This causes a
pressure differential which creates oscilations.
Reverse engineer this.  Exhaust pulses enters the foot, and a tuned mouth (a
NACA scoop?) would create negative pressure at the manifold.
7000rpm/60 = 117rps
117*6(rotor sides) = 700 Hz
700Hz @ a 160dB (guessing here now....)
Then baffles after the mouth to quiet the sound?
Standing waves may be a problem. Would there be a dead spot at 3500rpm
(350Hz)  If that's a problem, how do 2 stroke bikes get past that?  Is there
a frequency where the tuned exhaust creates a standing wave that the engine
must power through?
Anyway, flame away on this one..... I've got plenty more where this came
from :-)
Kevin

The Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2004 All world wide rights reserved.