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Hi Paul,
I imagine your plane will be rather loud without the exhaust splitters. Mine
is loud, with the exhaust splitters. No room for a muffler in my case. But
that stock manifold is bulletproof, no problems in 5 years and 500 hours.
paul wrote:
Hi, Ed and thanks for the info. I do not have the exhaust splitters...my
engine is a 1989 turbo model. I have the smaller 1988 cast iron manifold,
and including pipe, my total exhaust weight is 12 pounds. What appeals to
me most is that it is compact, simple, and I don't have to worry about thin
walled pipes glowing red inside my cowling, as the cast iron manifold
absorbs a lot of heat that would otherwise turn exhaust pipes red hot. Also,
being a pusher, my exhaust pipe need only be 8 inches long. Hoping to get
the DAR to inspect the first of the week. Take care, and I hope your new
exhaust system affords you lots of power as well as silencing. Paul Conner
----- Original Message -----
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, December 02, 2004 9:28 PM
Subject: [FlyRotary] Re: New Muffler Design
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
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