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Here are a couple of photos of the old and new
manifold on the aircraft. The new one has a much wider range of adjustment
tube length of from 6 1/2" of tubes to 11". The old one had a max of
9". However, I can only use about 9 3/4" before I bump into the cowl with
the air inlet elbow. So I will reshape that to lower its profile and see
If I can't get at least 10".
Went out around noon and fired it up with
an OAT of 85F got 5800 rpm static with the old manifold. Flew the old
manifold and got 6400 rpm at 2000 MSL and 6400 at 7000 msl. Landed and
proceeded to take off old manifold and put on new. Discovered I had failed
to remove a boss on the new one that interfered with the motor mount and had to
take it home and grind that off. Back out in the late afternoon and got
the new one installed. I tried several lengths of adjustment,
but this was just a quick and dirty and will need more testing to
confirm. But for what its worth these were the results
Length
Static Fuel
Flow
Calculated HP based on fuel burn
6 1/2"
5800 14.5
GPH OAT 87F 164.77
9"
6000
15.25 GPH OAT 87F
173.29
10"
6100 16.50
GPH OAT 88F 187.50
As Al pointed out, that fuel burn may
not quite as reliable a measure of HP for the rotary as it may be for a
piston engine The reason - you can keep cranking up (enriching)
the mixture once past a certain point and the fuel burn rate will increase but
you may not really be converting all of that increase into power - it could
simply be blown through the chamber and burnt in the exhaust
manifold.
I know when I continuing enrichment, my EGTs
come down after a certain point of enrichment - that leads me to believe that
excess fuel in the exhaust actually results in lesser temps - cools the exhaust
as counterintuitive as that seems. If this supposition is correct, then by
monitoring your EGTs you may be able to detect when that "excess" point is
reach. The end result may be a better estimate based on your observed fuel
burn rate.
I should have recorded the EGTs, but didn't think
of it at the time. Was in a hurry to get home so as not to miss
grilled steaks. Both were up in their normal range around
1650F.
In any case, at 6 lbs 3 0z this intake is lighter
by 4 lbs than the old one and I believe esthetically more pleasing to the
eye.
Couple of photos attached.
Will report flight results later.
Ed
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