As with most things, there is no one
best length. Answer depends on max RPM, what you want to optimize, how
much room you have, what prop is used (fixed or variable), how much money you
want to spend, etc.
With a fixed pitch prop I liked my
first system the best for a good combination of climb rate & speed.
Climb was at 6200 rpm. It had 16 - 17" runner length and did use a Dynamic
Chamber. Please don't make me or Ed rehash the DC again : )
My current manifold only has about
10.5" runners and gives up a little on climb rate but really starts to pull
strongly above 7000 rpm. "Cleanliness" is of course very
important.
Tracy
Tracy,
I promise not to
make you and Ed rehash the dynamic chamber. ;-)
I tried searching
the archives for every combination of runner, length, intake, tuning I could
think of and the results were not exactly what I was looking for. Now I'll
search for dynamic chamber and see what shows up.
I was looking at
my Renesis and thinking how nice it was that it was all put together and there
was nothing wrong with it. In a moment of weakness I considered leaving it that
way. Then after sleeping on it I decided it had to come apart to fix the oil
jets and de-carbon everything.....so I'll just stick with plan
A.
The problem with
my installation is the cowl is very tight and I only have room for two options
for intake length.
1.) Very short 9"
with the carbs right against the ports.
2.) Very long
20"+ with the carbs on the other side of the engine.
After reading
about Ed's experience with the short intakes I started to think maybe I should
go with the longer solution, in addition it should be better in
cruise.
The P-port should give enough power on the top
end that an intake optimized for mid range shouldn't hurt too
bad.
Of course a CS prop would solve most
problems including any surplus cash problem ;-).
The short system would probably have a higher
BSFC.
As
always....testing is the answer.
Monty