----- Original Message -----
Sent: Tuesday, April 05, 2005 4:42
PM
Subject: [FlyRotary] New manifold on
engine
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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