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Al, this enging run sounds very much like my first few iterations. To be honest, I cant really tell you exactly what I fixed to make it work. And I still don't have it quite as smooth as I want.
First fuel pressure is key. You want it lower. I have the same TWM fuel pressure regulator that you do. Make sure that it is hooked up to the manifold. You should be seeing pressures closer to 32psi at idle. I opened up the tension screw on the pressure regulator all the way. That gives me about 41 PSI with the engine off, up near 50 when running boost, and 32 at idle. Any test I made with higher fuel pressures made the situation much worse.
I also experimented with changing the transition point. A first I wanted to brin it down to run off all four injectors all the time (because they are dissimilar and I wasnt sure if they would handle a transition well. When I finally moved the transition back up, idle got better.
Try different configurations with the manifold pressure lines. Make SURE that each line is connected to all the runners/rotors. In my set up controller A samples both rotors right at the port, while controller B samples the pressure (from both runners T'd) just downstream of the throttle body. I find that A runs a little better on the ground and B seem to be a little smoother at altitude (though both work very well above 2000 RPM.
Keep playing with the MAP and work very hard to make sure there are no gaps. Use a wide Mode 2 band at first, then fine tune with a narrow one.
I finally got my to idle pretty good down to about 1200 or 1300 (sometimes 1000). It actually seems to run a little better when cold. Sometimes it runs exceedingly well and sounds like music. Sometimes not. But if it runs rough all I have to do lately is get it back above 1600 and it settles down.
Keep at it. If you want I will be working on mine all weekend and you can come down to MYF and hear it idle if interested.
Dave Leonard
>
> 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)
>
>
>
>
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