My 13b engine is ready to run....I ordered a VAM muffler, but since
it has
not yet happened, I was wondering if I could get away with using the
stock
cast iron manifold with a straight pipe attached to it, which would
exit
through the bottom of the cowling. I should mention that this is on a
pusher. George Graham told me that he was using a straight, (or
slightly
bent) pipe, and possibly Perry Mick is or was using the stock cast
iron
manifold?  My thinking is that although it is heavy, it might possibly
absorb a lot of the initial heat as it is exiting the exhaust ports,
acting
like a heat collector, and I might not need expensive inconel or 321
stainless after the exhaust goes through the stock manifold first?
Would
the cast iron manifold absorb much of the heat and possibly muffle
some of
the noise as it is bounced around inside of the stock manifold?  I'm
probably grasping at straws, but with all the knowledge and
experience in
this group, I figure it wouldn't hurt to ask.  Thanks to all for your
opinions and advice.  Paul Conner, 13b powered SQ2000

The stock exhaust manifold is very good at reducing noise, if you have
room you may want to consider a racing beat header...

Jerry Bass wrote:

I just tried a dual two inch pipe into a 3" pipe for my RV6A-R and got noise complaints from the neighbors around the airport. I then added 4 - 2" SS tubes cross wise inside the three inch pipe and it quited down, but got more complaints. I ordered a SpinTech muffler for the out pipe.

New Regs, coming in June say Certificated planes should be less than 70db. Wow, How they going to do that?

So, your cast iron maniflold and short pipe may be too loud too.

Jerry Bass
540-932 3125
Cell 241-2675--

Are you sure it is all engine noise Jerry? What is your prop diameter
and what RPM do you take off at? You need to enlist some help there
and get a Radio Shack DB meter to monitor different take off RPM
settings

>from the ground. An AT6 or a Cessna 210 206 with a constant speed prop

are very noisy because the tips are going transonic.

Paul Lamar

Jerry Bass wrote:

I should have added that when I tested the VAM pipe, it was quiet to 50 mph on the ground.  The Air thru the VAM must make it quieter. While I did not fly the plane with the VAM pipe, it may have been too loud too.  I did not use the cast iron manifold.

Jerry Bass
540-932 3125
Cell 241-2675

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