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)