8-22-04
1.1 hours / 29.7 total
Took the plane up
for some testing today, and believe I’ve found that it isn’t putting out the
power I’d hoped for. I couldn’t tell if the low MAP readings
were real or not, but now I think they are.
First, the takeoff
was less eventful. I very slowly
added power until I got going fast enough to raise the tail. At that point, it was easy to add
throttle and adjust the rudder to match.
Piece of cake, though I will still plan to shim the mount at some
point. In cruise, the ball is just
about the same amount off as it was with the previous B drive version, so the
left mount offset doesn’t see to have that much effect on cruise. Need to start thinking about a trim
tab though.
Climb at 130 mph was
only about 1200 fpm, at 5800 rpm, and a MAP of 24.5 around 1500 ft MSL.
Tracy was reporting 6200 rpm
at 120-130, so I’m clearly below his 13B
performance.
Climb at 100 mph was
about 2400 fpm, at about 5600 rpm, but I didn’t note the MAP. I might have gotten a little more climb
rate from 90 mph, but the oil temps rang the bell on the EM-2. They seemed to want to stay in the 215
range after a few thousand feet (97 degrees on the ground), though the water
temps were still OK. I removed the
rear bulkheads of the cowl cheeks for the next test.
Full throttle at 7k
ft was a dismal 190 mph TAS, at 6200 rpm.
I think this was a step backwards from the B drive.
My conclusion is
that the engine isn’t making enough power for the current prop and redrive. I’m starting to believe the low MAP
readings are real, and not an error from the port placement. Eventually, this will mean intake #4,
and an new inlet scheme, but perhaps not right now.
Finally, I brought
the muffler home to weld on a tailpipe.
The slipstream is blowing the exhaust on the bottom of the fuselage,
right under my butt. I’m also
smelling a little more exhaust than I care to, so this will help eliminate that
as well. It will also perhaps
reduce the sound in the cockpit as well.
The best news is
that the engine continues to run flawlessly, though not as powerfully as I’d like.