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Hi Paul,
Makes sense that the iron manifold would transmit less noise through it
walls than a thin walled tube. Also, keep in mind that the 6 port with the
exhaust splitter in the exhaust port knocks down the exhaust bark by 8 dB
according to the Mazda engineers (over a port with no splitter such as the
turbo housing). Can't recall your model engine but I know that Perry runs a
six port. The turbo 4 port without the exhaust port splitter presents a
somewhat greater challenge in knocking down the noise level. Indeed, if my
new exhaust system did knock my noise level down by 10 db (as the
measurements indicate) that puts me only slightly less noisy than a six
port with no muffler {:>(.
I believe that Tracy (whose old 13B also had the turbo housings) remarked
several times that on reconsideration, he was more than willing to give up
an small power gain from the perhaps better flow through the exhaust port
(without the splitter) ignored to not to have to deal with the turbo
housings exhaust noise level. Its fairly brutal.
If your noise level is acceptable then I certainly would not be inclined to
do anything at this point. The only gain you might achieve is perhaps a
lighter exhaust system - and whether a few pounds there is worth it - only
you can determine.
Waiting to hear about your first flight!!
Ed Anderson
----- Original Message -----
From: "paul" <sqpilot@bellsouth.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, December 02, 2004 6:03 PM
Subject: [FlyRotary] Re: New Muffler Design
> Thanks for the info, Ed....One point of interest is that I have the stock
> cast iron manifold inbetween the engine and my tailpipe. It would seem
that
> the cast iron manifold is absorbing a lot of impulses, because everyone
who
> has heard my engine run states that it is not that loud. Perry Mick
> mentioned that he has a standard exhaust pipe following his cast iron
> manifold as well, and has had no problems with it in the few hundred hours
> he has flown with that setup. (He told me that when I was inquiring about
> the need for stainless exhaust pipe after the cast iron manifold). Don't
> know how much energy the cast iron absorbs, but it definately absorbs the
> heat so the pipe doesen't get as hot. Curious minds want to know. Take
> care. Paul Conner
>
> ----- Original Message -----
> From: "Ed Anderson" <eanderson@carolina.rr.com>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Wednesday, December 01, 2004 10:25 AM
> Subject: [FlyRotary] Re: New Muffler Design
>
>
> > Hi Paul,
> >
> > Have had not experience with Supertrapp mufflers although I have looked
> at
> > them several times. I had at least one rotary friend that tried them
and
> > found them unsatisfactory - loud. But, of course, they are "tunable" by
> > inserting fewer or more discs - so could be he just did not have it
tuned.
> >
> > I am uncertain about how well they would hold up - the rotary turbo
> housings
> > ( without using a turbo) put out a pretty brutal shock wave and I have
> had
> > it break apart a mild steel insert into small pieces as well as fatigue
> fail
> > the metal at the end of my muffler tubes. I know that Tracy had at
least
> > one of his home made mufflers fail due to the stress.
> >
> > However, perhaps some of the RX-7 drivers could give you some
information
> of
> > how well they do.
> >
> > Ed
> > ----- Original Message -----
> > From: "paul" <sqpilot@bellsouth.net>
> > To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> > Sent: Wednesday, December 01, 2004 11:11 AM
> > Subject: [FlyRotary] New Muffler Design
> >
> >
> > > Hi, Ed....funny you should mention that....I was just considering
> ordering
> > a
> > > Supertrapp disc muffler which soulds somewhat similar to what you are
> > doing,
> > > with the exception that it just attaches to the rear of your pipe.
The
> > one
> > > that I am interested in is the 3" diffuser disc unit, as seen on
> > > www.http://recerpartswholesale.com/supert2.htm One of my concerns,
> > however
> > > is how well it might hold up, as any parts/pieces of a failed unit
would
> > go
> > > through my prop (pusher configuration), effectively cutting my flight
> > short
> > > and/or ruining my day. Good luck with flight testing, etc. Please
keep
> > us
> > > posted. Paul Conner
> > >
> > >
> > >
> > > >> Homepage: http://www.flyrotary.com/
> > > >> Archive: http://lancaironline.net/lists/flyrotary/List.html
> >
> >
> >
> > >> Homepage: http://www.flyrotary.com/
> > >> Archive: http://lancaironline.net/lists/flyrotary/List.html
> >
>
>
> >> Homepage: http://www.flyrotary.com/
> >> Archive: http://lancaironline.net/lists/flyrotary/List.html
>
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