I
guess I have now done what I’d consider the first serious runs of the engine
on the plane, and I have so many question marks in my head, it’s hard to know
what to address next.
The biggest issue
is; I cannot get smooth running up to about 2200 rpm; which is as far as I
went. At about 2000 I adjusted mixture from too lean to too rich, and
nowhere does it smooth out completely – some roughness, mild surging. At
lower rpm, 1000 – 1500 it is quite rough and unsteady, which is disconcerting
in itself, but worrisome when it goes through periods of torsional vibration
with the reduction gear backlash, which is noisy and shakes the
plane.
Of course it brings
back the recent discussions of you other guys with the 550 injectors in the
primary. I kind of glossed over that because I recalled smooth running
on the dyno. In hindsight now, I think the operator figured out early-on
that to keep it smooth he needed to keep some load on – just turn the load
knob a little and it was fine. And on the dyno when it wasn’t running
smooth, no big deal – no redrive to backlash, and the engine is bolted down in
the next room. You could just hear that it wasn’t running
smooth.
Still, I suspect
something is different now; and perhaps you’ll indulge my dumping, and pass on
a clue or two.
At 2000 I’m seeing
a 13.1 MAP reading. Seems low to me. Is it? That puts it below the
stage point, yet when I turned off the primary injectors, it continued to run;
just rougher. Same effect turning off the secondaries. Hotest EGT
was at about 1100, lowest about 980. Bigger spread than I ever saw on
the dyno runs, but the data we took there was always under higher
load.
Fuel pressure reads
50 psi, TWM tells me it came to me preset at 43.5. When the coolant temp
read 125 when the pipes and rad tanks were just about too hot to touch, which
I guessed to be more like 140. I’m suspicious of just about every
readout. Later when the WT read 140, the CHT TC that measure temps in and out
of the rads were reading about 85. I believed backup gauges were
unnecessary.
Oh yeah; the
mixture bar reads just about full scale all the time, even when the engine is
about to die from being too lean. I have a different heated Bosch
sensor, which I assumed would have the same 0-1volt range. Maybe
not. Is the sensor output voltage low when lean or rich? With the
engine off and sensor heated I measured .052 volts. I tried to get a
reading with the engine running, but all I got was about .025 and I can’t be
certain I had contact with the lead – and with the prop spinning so close by I
didn’t spend too much time trying.
One other major
concern. With hot oil (150) at the filter block where the feed goes to
the redrive, the ¼” Al line to the redrive was hardly above ambient temp a
minute or two after shutdown; suggesting little or no flow was going
there. Oil pressure was in the 90’s. I’m not aware that there is
an orifice in there. This has me a bit baffled.
Oil pressure,
coolant pressure, Oil temp seem fine.
Maybe I should go
to a movie.
Al (not
ecstatic)