We'll I finally got some time off to check out my airplane after the
round trip from
Everett to Medford. The heat cooked my left brake line, and I suspected
the muffler
had too much back pressure, so I resolved to investigate. Here's what I
found when I
removed my Hushpower from the airplane. There is way too much heat
coming off my
muffler- the powder coating on my engine mount is cooked near the
exhaust pipes, even
though I coverd them with fiberfrax and placed a SS heat sheild to cover
the tubes
from view of the exhaust. The muffler was making like a baby rattle so I
cut it open
and this stuff came out of the inlet side. I'll send more pictures of
the innards.
What I have is an RV-4 with the radiators and oil cooler hung underneath
the plane in
a scoop that is reminiscent of a P-51. I had the muffler submerged under the
fuselage. I"m thinking that it would be better to have the exhaust pipes
exit the
side of the cowl, in a reverse scoop that would vent a huge amount of
heat from the
cowl. The muffler would be a straight 6 foot muffler like the one Paul
outlined about
a week ago. It would be mounted along the side of the fuselage. I hate
to ruin the
clean lines of an RV-4, but nothing would ruin it more than having a
mechanical
failure due to excessive exhaust heat bringing the plane down. My
biggest worry about
this rotary conversion is excessive exhaust heat and how to manage it
effectively.
Here is the muffler cut open. The red chunks are what is left of the melted
insulation material between the perforated inner case and outer. The
outer case
showed signs of bulging. The perforated inner case was split on the seam
closest to
the camera. The inner cone material which is also perforated was mostly
gone, but big
chunks were still left inside the muffler and undoubtedly were causing
some obstruction.
Here's the split in the inner perforated case. Not real confidence
inspiring.
Crap that I shook out of my baby rattle/Hushpower muffler.
Brian Trubee
That will work out OK but I would put it on the bottom like Mike did.
I think you could get the rad under the engine.
Either that or use a narrower rad and put it next to the rad under the fuse.
Paul Lamar
I'd better take some time to think about it- running the exhaust under
the fuselage,
around engine mount tubes, near the coolant lines, near the radiator, making
allowances for cooling duct considerations, etc, not to mention
momentary cash flow
situation etc. I'm inclined to just exit out the side of the cowl- makes
all those
considerations other than $ easy to address.
Brian Trubee
I am not sure you have enough room to do it this way but it is sort of
what Mike
wound up with. He had the advantage of his motor mount being further
back. These are
two inch tubes with 3 inch CL radius bends. If you have Wagner pipes the
bend CL
radius is bit tighter and the OD is 1 7/8" as I recall. Under the
engines the tubes
can be side by side. I'll modify the 3D for that.
BTW we might make it up there next week. We will try to go from SFO to
SEATAC
on Monday. I put your number in my cell.
Paul Lamar
Here is what it looks like side by side under the engine.
Perhaps it is possible to shorten the top pipe a bit more.
That is the great thing about 3D. It is quicker than doing it with hardware.
Paul Lamar
This is certainly the nicest time of year up here in my opinion. It
would be great if you could get out to see the plane. I'd take you up
for a flight if it were currently airworthy.
Brian
Not going to make it this time Brian.
Paul Lamar
Ok, I've got a good idea now of how I'm going to configure my new
exhaust system- going with the co-axial muffler w/ cool air augmenter.
It's going under the plane in the same place as the old muffler, but
it's a bit longer so it'll be hung slightly different. I'm also going to
put a fairly large exit scoop adjacent to my header pipes, I'm seeing a
lot of heat damage from the superheated air coming off the headers, I
need to get that heat out of the cowl expeditiously.
Since you can't make it out this way, I'll send some photos of my progress
Brian
OK Brian
Thanks for sending pictures.
Paul Lamar
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