BIG SNIP...

to line up tennis balls (pulses) rolling thru the exhaust

pipe. An individual  18" pipe will be specifically tuned for a certain

narrow

rpm band, wheras a reasonably designed muffler collector will have a

much

broader band and will make more hp throughout the band.

Using a rubber isolator will probably work much better than a loose

metal

restraint, but you'll still transmit vibration into the fuselage because

you

need to make it rigid enough to stop (dampen) a fatique failure. Mark

Sedikas

who is an aircraft certified welder is constantly repairing SS exhaust

systems

for Lyco and Cont, and they run 100-200 F less temp than a rotary, so

I'm a big

supporter of Inconel which is a one time job and a safe method.  I hope

I'm not

be a pain, but an exhaust failure can be catastrophic.

Chuck Harbert

Ed Anderson wrote:

Chuck,

You'll get no argument from me about needing to be careful and safe
regarding the Mazda's exhaust.  The scavenging effect of tying two pipes
together has been clearly shown to be beneficial.  When I was doing my
research (about 7 years back before we had this method of exchanging ideas
and experiences), all the books I read indicated that any "back pressure"
was much more detrimental to a rotary's performance  than a reciprocating
engine.  Being somewhat less knowledgeable then and no one around to ask,
less back pressure equated to minimum restriction in the exhaust path.
Therefore, I ended up with 2" dia headers and straight through mufflers.  I
now know that using the collector approach can result in even less back
pressure because of the scavenging effect your tennis balls demonstrates so
well.

   By adding the 18" extension to the 14" of my headers I come close to the
31" that has been mentioned as suitable for the 6000 rpm range.  So I
thought I would give it a try.  Appreciate your suggestions and I no longer
have the mufflers hanging under the fuselage.  No mufflers at all, which is
just too loud for my ears, so I am going to try the "Hole and Fishtail"
approach.

  By the way, how is your repair coming along?  I understand that you are
taking a stand down period, but hope you get back into the air soon.  (I
presume you will use a different make oil cooler).

Best Regards

Ed Anderson

 
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