Perry Mick wrote:

Awhile back I replaced the intake manifold from the engine to the
dynamic chamber, retaining the stock dynamic chamber. The runners were a
little longer than stock but I thought I would get more power from that,
but did not, lost a little power.

For the last week I've been building a dynamic chamber replacement.  It
is just a box with the roughly the same external dimensions as the stock
dynamic chamber, same bolt pattern, hole pattern, etc. so it just bolted
in. Didn't know what to expect.  Flew it this evening.  If anything
things have very slightly improved. Engine seems to run smoother and I
seem to have a little more at the top end in cruise.  Didn't notice much
improvement at climb. Got a couple more pounds out of the installation.

I made one side removable so I can go back in and add bell-mouths - will
report on that later.

--
Perry Mick
Custom Composite Props
mick@bridgingworlds.com
http://www.ductedfan.com

What are the current lengths of the runners Perry? If you tune them for your top
RPM which for your direct drive installation must be down around
5000 RPM you should get more power. Dynamic chambers basically double the
the lengths of the runners. My guess for 5000 RPM runner length
is about 24 inches. It is somewhat a function of diameter as well.
I think you would gain more by making the insides of the runners
as smooth as possible. That enhances the air flow velocity.

Got any pictures of the latest configuration?

Paul Lamar

I'll have to try to get good measurements on the original and new
lengths. No photos yet.  We are looking into digital cameras.  Maybe
Mike McGee can come over take some shots sometime.

Top RPM before the changes was 5500.  After the first change it was down
to 5350 or so, I was seeing 5400 yesterday after the dynamic chamber change.

--
Perry Mick
Custom Composite Props
mick@bridgingworlds.com
http://www.ductedfan.com

A used Sony Mavica FD73 MVC FD73 from ebay would be a good choice.
Are you recording OAT and humidity? Do you have an air cleaner?
Is you air intake the same configuration in all cases?

Paul Lamar
 
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