201Steve Posted December 27, 2018 Report Share Posted December 27, 2018 Take a look at video. ‘77 J. Cruise flight. Power and fuel settings appear to be no factor, but this was at WOT, 2500RPM, approx 40 LOP. 8DAB7920-A024-4A0A-9474-BADF8A04B191.MOV Quote Link to comment Share on other sites More sharing options...
Oldguy Posted December 27, 2018 Report Share Posted December 27, 2018 You don't happen to have a recording engine monitor, do you? Comparing what it shows versus the display might be the first place to look. Quote Link to comment Share on other sites More sharing options...
201Steve Posted December 27, 2018 Author Report Share Posted December 27, 2018 Also, here is engine monitor. Quote Link to comment Share on other sites More sharing options...
takair Posted December 27, 2018 Report Share Posted December 27, 2018 Almost looks like a problem with the tach. Would check the harness and connectors first. What’s going on with fuel pressure at the end of the clip? Quote Link to comment Share on other sites More sharing options...
201Steve Posted December 27, 2018 Author Report Share Posted December 27, 2018 Good call on the fuel pressure. I had forgotten that had happened. Here is a full instrument scan where the fuel pressure is moving again. It didn’t seem to have a correlation but maybe another thing to keep an eye on 11566D6A-61C2-476E-964C-1F9485AAC222.MOV Quote Link to comment Share on other sites More sharing options...
Guest Posted December 27, 2018 Report Share Posted December 27, 2018 In your first video, as well as fuel pressure the old Alcor EGT wanders almost in sync with the tachometer. Clarence Quote Link to comment Share on other sites More sharing options...
LANCECASPER Posted December 27, 2018 Report Share Posted December 27, 2018 23 minutes ago, 201Steve said: Good call on the fuel pressure. I had forgotten that had happened. Here is a full instrument scan where the fuel pressure is moving again. It didn’t seem to have a correlation but maybe another thing to keep an eye on 11566D6A-61C2-476E-964C-1F9485AAC222.MOV Were your strobes on? If so, try it again with the strobes off just to see if there's a ground issue. 3 Quote Link to comment Share on other sites More sharing options...
201Steve Posted December 28, 2018 Author Report Share Posted December 28, 2018 29 minutes ago, LANCECASPER said: Were your strobes on? If so, try it again with the strobes off just to see if there's a ground issue. Yes. Strobe on. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 28, 2018 Report Share Posted December 28, 2018 Dial up the smartphone app... audio based tachometer... See if you can prove/disprove the ship’s gauge... Do you hear anything changing? PP thoughts, not a mechanic... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
201Steve Posted December 30, 2018 Author Report Share Posted December 30, 2018 On 12/27/2018 at 6:34 PM, M20Doc said: In your first video, as well as fuel pressure the old Alcor EGT wanders almost in sync with the tachometer. Clarence All 3 seem to be goofing out a bit. Fuel Pressure, RPM, and Alcor EGT. The insight egt moves a little, but I figure there’s no way you get a constant EGT temp to the “T”. Or I wouldn’t think. Quote Link to comment Share on other sites More sharing options...
Guest Posted December 30, 2018 Report Share Posted December 30, 2018 I believe that your fuel pressure gauge is a mechanical gauge, so the pressure may indeed be wandering. I don’t think it would affect EGT, the servo should be able to handle some variation in pressures. Your G1 engine monitor sadly doesn’t have data logging from what I read on Insight Avionics The tachometer is electric driven by magneto impulses from the P lead circuit. With a constant speed propeller, I don’t think the RPM would change unless the governor isn’t able to keep up. Do you feel/ hear a change in engine performance? Clarence Quote Link to comment Share on other sites More sharing options...
201Steve Posted December 31, 2018 Author Report Share Posted December 31, 2018 On 12/29/2018 at 8:43 PM, M20Doc said: I believe that your fuel pressure gauge is a mechanical gauge, so the pressure may indeed be wandering. I don’t think it would affect EGT, the servo should be able to handle some variation in pressures. Your G1 engine monitor sadly doesn’t have data logging from what I read on Insight Avionics The tachometer is electric driven by magneto impulses from the P lead circuit. With a constant speed propeller, I don’t think the RPM would change unless the governor isn’t able to keep up. Do you feel/ hear a change in engine performance? Clarence I’m hearing an occasional variation in sound/feel. It is maybe once or twice every 10-20 minutes. It’s very short, so by the time I start scanning and checking instruments, I can’t correlate it to fluctuation. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 31, 2018 Report Share Posted December 31, 2018 Well Steve, That does sound unusual... If I heard something that sounded like an uncommanded change in engine operation, my HR would start to increase... Doing that every 10-20 minutes would lead to discomfort. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Rick Junkin Posted December 31, 2018 Report Share Posted December 31, 2018 40 LOP = low fuel flow. The fuel pressure fluctuation looks pretty smooth, so it probably wouldn't be fuel percolation, right? Does it behave the same if you run ROP? Cheers, Rick Quote Link to comment Share on other sites More sharing options...
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