Mat,
Picked up the muffler that Chris uses and I am
amazed that it works. Chris seems to have a gift of falling on his
feet. It is very simple and he claims it is very quiet, but with
a slight power loss. Will photograph it, but is based on an ATC
OZ muffler. Checked my DB readings last week, and only got as far
as 3000 RPM which is the quiet range! 2000 RPM 85 DB 2500 RPM
95 DB, 3000 rpm 100 DB and outside the cab 110 DB. NO wonder
at full noise it gets annoying. Obviously my system is useless
for noise reduction, with certainly no back pressure at all. I am
guessing that to have noise reduction I will have to wear some
restriction which is power loss. Same story -- just what
compromise can I live with?
Will attempt to describe the muffler once I have measured it on
the bench. MY thanks to Chris for loaning this to me.
Neil.
Have started on the exhaust. Made
all three primaries 2" double slip joints (that alone took
almost a whole day with welder). The big can (CA - Centrifugal Accumulator) rolled into a
5" can and we'll secure it to the engine with straps.
The inside pipe is 2.75"
which has an area of 5.94sq". I'm not sure if there's a magic
number, but all the holes I drilled equaled to just under
double the area (11sq"). Most are 3/8, but I did add some 1/2
to get the total area up. Could we get away with drilling less holes? Not
sure. I'll be able to drill out one side end of the CA and
pull out the inner tube and change out. Will experiment later with less holes and
monitor back pressure. Will weld a npt bung on the CA and use
the wideband bung to measure the different.
The previous exhaust with
just an Aero Turbine
2525XL, measured ~113dBA. With nothing, was closer to 120dBA.
Funny around 2000 prop rpm was louder then at 2300 full
static.
- Matt Boiteau
On 2020-01-07
12:19:23 AM, Matt Boiteau mattboiteau@gmail.com
<flyrotary@lancaironline.net> wrote:
Okay I'll make all 3 primary tubes (2" diameter) all
double slip fit. Welding batwing tabs (picture
below) on to either side on the slips, will hold the
muffler to the header but allow expansion.
Having
troubles finding 2.75" bends in 321, so I might have
to just switch to 3" downpipe that is more common.
Vband clamp before downpipe for easier removal and
under the plane to allow adding additional exhaust
setups (long pipe with holes drilled in it, fishmouth
tailpipe, etc)
Batwing tabs
- Matt Boiteau
On
2020-01-03 4:22:18 PM, Neil Unger 12348ung@gmail.com
<flyrotary@lancaironline.net> wrote:
Mat,
As usual I have no idea. I made
all 3 slip joints and to date no grief in that
area. I am coming around to the stock manifold in
some way. Yes it is heavy, but appears to muffle
the noise as well. Know of 2 installations that use
the stock manifold with a simple muffler after and
both claim "acceptable" noise. It appears that the
stock manifold has a big influence on noise?? Would
prefer a DB reading, but if not available it is what
it is. All is compromise, weight, cost, time, but
at the end of the day it has to work.
Still working on the turbo even though the world is
on holidays. All to save my hearing. So far the
rotary is definitely "unique" as far as a turbo is
concerned. The heat generated exceeds all else.
Two things to date -- special exhaust wheel and
water cooled bearing body =, all for heat. Have
modified the stock front plate on the renesis to
take an electric water pump. That is the simple
bit.
Neil.
okay I
found a good company called SPD Exhaust. They have
everything you need in 321ss.
With the engine being an RX8, we have three
exhaust ports. Should I weld the front and back
solid to the muffler, and make the middle one a
slip fit for expansion? Or vice-vesa?
- Matt Boiteau
On
2019-12-28 11:03:42 AM, Finn Lassen finn.lassen@verizon.net
<flyrotary@lancaironline.net>
wrote:
I did something
similar with my RV-3 13B decades ago. It
split open at the welds around one of the
pipes from the manifold into the the big
outer tube. True, it did use individual
manifold base plates, not the connected
factory manifold and the big tube was only
0.035.
Still, I would recommend slip joints on two
of the three pipes, like I added on one of
the pipes (cut through and a surrounding
bigger pipe -- missing in picture).
Can't remember why I went from the above to
individual runners into a perforated pipe
under the fuselage. Probably got lured by
promise of increased power by tuned lengths
and still uncomfortable by the muffler being
inside the cowling.
Finn
On 12/28/2019 12:10 AM, Matt Boiteau mattboiteau@gmail.com
wrote:
This is what I'm
going to try in a few weeks.
" Exhaust
valve opens and a pulse of hot gas puffs
out through a short pipe, then tangentially into
a cylindrical canister. Being
tangential, the pulse flattens out and
travels helically (rather
than bouncing and reverberating around)
along the inside curved wall of the can,
spiraling toward the exit, where it
comes out more uniform in flow and so
pretty quiet."
Outer pipe = 321 ss 0.050 thick. Flat
plate bent to a 5" tube
Inner pipe = 321 ss 0.036 thick. 2.5"
diameter
(I might use
302ss 0.065 since I already have it)
From my understanding, the area of
the holes should be double the area of
the inner pipe.
- Matt Boiteau
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