M20C cruise vibration

[BKlott]

19 hours ago, LucasC said:

I had some prop work done in sept. Sent out to prop shop to have a ding blended out. I was thinking it may be that. Im going to play with the mixture next time im up and a few other checks then im going to get it dynamically balanced. Just cant remember feeling it so bad.

 

How big was the “ding” and what caused it? May be something else going on here.

[Shadrach]

What are you using as a reference to lean?  With the extreme cold and high pressures in your area, you're seeing DA' of -3500'msl maybe even lower. Is it possible that you are over leaning?  Your 180hp lycoming will make ~110% of rated power under those conditions.  

[LucasC]

Update. Went flying today. Was 10 degrees f on the ground. Ran great in climb. Once i leveled off and got into my cruise setting i did have a vibration after the initial stumbling of engine during leaning. I brought mixture in about an inch more and vibration went away mostly. 

[Shadrach]

47 minutes ago, LucasC said:

Update. Went flying today. Was 10 degrees f on the ground. Ran great in climb. Once i leveled off and got into my cruise setting i did have a vibration after the initial stumbling of engine during leaning. I brought mixture in about an inch more and vibration went away mostly. 

 

My engine gets rough too if I pull the mixture out far enough. It smooths out if I enrichen. Is that OK? From that info can you help me diagnose the health of my fuel delivery system?

[Andy95W]

Lucas- cold air is a lot thicker than warm, so it'll need more fuel.  If you lean it a "normal" amount it'll be too lean and you'll get the roughness you experienced.  Mixture notwithstanding, my C also seems to run rougher the colder it gets.

[3914N]

This thread is a good reminder that the “rule of thumb” mixture positions those of us without engine monitors use on a daily basis may not be correct in abnormally high or low temps. I’ve shocked myself how far out I need to pull the mixture in cruise on a really warm day. Seems like this was the opposite problem. 

[Hank]

1 hour ago, 3914N said:

This thread is a good reminder that the “rule of thumb” mixture positions those of us without engine monitors use on a daily basis may not be correct in abnormally high or low temps. I’ve shocked myself how far out I need to pull the mixture in cruise on a really warm day. Seems like this was the opposite problem. 

Flying around down here, my mixture is often 2/3 towards Idle Cutoff . . . .

[Hank]

5 hours ago, bluehighwayflyer said:

Having flown my previous M20J for the past dozen years or so LOP, I had gotten a little rusty on (or perhaps just too lazy for) ROP ops.  So since I recently transitioned back into our M20C I have just been relying on MAPA’s “key” number of 47 (actually conservatively using 44 or 45 since our engine instrumentation sucks to insure I’m around 60 percent power where I can do no harm with the mixture) and then I’m just leaning til rough and then enrichening til smooth. The engine seems happy and from what instrumentation I do have, the temps all look good, and the fuel flow seems about right based upon what I am putting in at the pump.  Best of all it is almost as easy as flying LOP based on fuel flow used to be.

Perhaps you should just try that, too, Lucas, until, like me, you can get some better engine instrumentation installed.  I bet your engine is fine and that it is your leaning technique that has room for improvement.  

Jim

I fly at 46, or as close as I can get at altitude with 2500 RPM. Except I lean using the single factory EGT value. It can go to about 25°F LOP up high, but speed really drops off.

[Hank]

2 hours ago, bluehighwayflyer said:

Thanks, Hank.  I had read a few of your old posts about M20C engine operation and have taken them to heart.  

I’m only finding the C to be about 10 knots slower than the J at 8 GPH.   Ours is bone stock aerodynamically except for the brake caliper rotation mod but it has a fresh roller tapet engine and a PowerFlow exhaust.  Not too shabby.   

EDM-900 going in after I absorb the new interior I am currently putting in and the tailbeacon I just ordered.

Jim

We should get together and compare notes, even check performance in the air together. If you're through cleaning up your home and farm after Michael.