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.