Ken Powell wrote:
Chuck,
Hope you don't mind me adding my thoughts to why you don't seem to be
making more HP. It's possible that your intake pipes are too long (they
look 'long' in the pictures that I have seen of your engine bay). Seems
that others here on the newsletter have suggested that 20" seemed to work
best for 6000 - 6500 RPM; I plan to make my pipes in 2 pieces so that I can
add /subtract to the length and can experiment with lengths between 18" and
24". Tracy, how long is your intake from the rotor housing to the plenum?
Ken Powell
kenpowell@aristotle.net
I think that might be a good call Ken. That could also explain
why it has enough torque to power the prop past stall at 4700
engine RPM.
That silly oil filler pipe and dip stick might get in the way of
optimum pipe length on a low cowl aircraft installation. Perhaps
I can come up with a new filler pipe welded into the back of the
pan near the firewall. The dip stick can be fastened to the cap.
Paul Lamar
Ed Anderson wrote:
My copy of Tracy's intake system has a runner length of 19-23" inches -
suppose to be good for peak power around 6000 rpm at 19". I installed
tubes inside tubes (see attached photo) so I could adjust the length to fine
tune it. Right now I am flying at its longest length (approx 23") to get
power at lower rpms for take off. Don't know if it is the reason, but, I
have noticed the same "stalled" prop condition that Chuck mentioned about
prop loading up on take off roll and the rpm dropping approx 300-400 rpm.
Perhaps, since my tube lengths are shorter than Chuck's, perhaps that is
why I find my static rpm at 5600 vice Chuck's at 4700 rpm.
I intend to reduce the length of the tube to 19" this month and see what
effect that has on rpm.
Perhaps as Paul suggested - the long pipes move the best power point down in
rpm and the increased torque at that point is sufficient to turn the prop
past its max load point and we get the "stalled" prop. Interesting that
Chuck and I both have the long small pipes and have encountered this
phenomenon. Tracy's runner length appears to be slightly shorter than
either mine or Chucks and I have not hear him mention any "Stalled prop"
condition.
FWIW
Ed Anderson
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