Bolter Posted August 30, 2012 Report Posted August 30, 2012 I was talking LOP with a friend while up in his C-172. He has an IO-360, but I was not sure how to go about trying out LOP when the power can't be set without changing the RPM. We did an experiment with low RPM in lieu of dropping power, so that nothing would get hurt from the LOP operation if we made a mistake. When leaning, the RPM kept dropping, so it was a chase between throttle and mixture, and became impractical. We did watch 3 of 4 cylinder peak and go down again nicely, though. Cylinder #1 was way out of sync with the rest, so it would grossly fail the Gami spread test, but we were also changing rpm from 1500 rpm to 2200 rpm, trying to make something happen. Does anyone have LOP experience without the constant speed prop we Mooney pilots take for granted? -dan
KSMooniac Posted August 31, 2012 Report Posted August 31, 2012 How about just trying it at WOT during cruise? The RPMs will come down since going LOP means reducing power from the ROP setting at WOT, or any throttle setting for that matter.
jetdriven Posted August 31, 2012 Report Posted August 31, 2012 Try removing and cleaning those injectors in Hoppes #9, then reinstaling carefully. I have done that twice and went from a ~1 GPH GAMI spread to around .2 GPH. Your friend's IO-360 is a parallel-valve engine, however.
Parker_Woodruff Posted August 31, 2012 Report Posted August 31, 2012 Quote: tomcullen Does anyone have LOP experience without the constant speed prop we Mooney pilots take for granted? -dan
jetdriven Posted August 31, 2012 Report Posted August 31, 2012 Parker, does that IO-360 on the 172R/S have a tuned intake system?
Bolter Posted August 31, 2012 Author Report Posted August 31, 2012 Thanks for all the feedback. Parker: This was a fairly new 172 with the G1000 setup displaying all 4 EGT's and fuel flow. I admit I don't know if it was a genuine fuel flow sensor or not, but I would hope so on such a sophisticated panel. Byron: A fuel injector cleaning may be the thing regardless of LOP or ROP, though they run similar EGT's at ROP settings. I thought there may be something funny because of the slow RPM at the same time. I have seen thay my engine LOP characteristics change with 100 rpm differences. Sometimes it likes 2500, sometimes 2400. Scott: WOT is a possiblity, but I was scared that we might be making too much power and risking a problem if we played aggressively with mixture. Just being cautious, like the first LOP experiment on my plane. In hindsight, we could have used fuel flow to estimate percent power pretty easily. Future plan: limit power via fuel flow, and be aggressive with the throttle to keep up RPM while watching EGT's peak and see what we get? -dan
N601RX Posted August 31, 2012 Report Posted August 31, 2012 Has anyone tried indexing the injector air hole in different orinetations to see it small tweeks can be made to the fuel flow balance? Lycoming recommends straight up to help with fuel seemage when the engine is hot, but I have no idea if flow is slightly affected by angular orientation. It might be worth experimenting with.
jetdriven Posted August 31, 2012 Report Posted August 31, 2012 The "A" stamped on the injector needs to be within 30 degrees of the lower side. I have had good luck swapping injectors around to even the mixture distribution out. To run LOP since you have all 4 CHT and EGT, leave it WOT, pull the mixture quickly to rough, then enrich to smooth. If FF is below 9.0 GPH then you are running less than 75% power (the engine is derated by RPM from 180 HP). Sound familiar? You might have been running LOP all this time....
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