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Engine management / leaning / peak / lean of peak (merged)

giving back 2-3 twists to enrich you should be in the ballpark of -50* F LOP EGT?

Maybe, maybe not…
It has been my experience flying different engines in different aircraft, that some can’t be leaned LOP. Carb and mags equipped engines generally don‘t like to go into LOP. The best configuration to take advantage of the procedure is an injected/electronic ignition engine. Also note that the air inlet, air filter, etc, may also influence the capability.

Sidenote
Jim Petty has a fantastic little iOS app called AircraftPower. I use it mostly in flight to determine or set the power settings since my instrumentation is pretty basic (engine parameters on a VM1000). Sure beats reading lines on the Lycoming tables
And the app is FREE!

Last Edited by Dan at 15 Oct 11:48
Dan
ain't the Destination, but the Journey
LSZF, Switzerland

@igor wrote

Am I understood correctly, that by leaning until roughness and then giving back 2-3 twists to enrich you should be in the ballpark of -50* F LOP EGT?

I think what you describe is more 50-150 rich of peak?!

On a NA carb. engine you can try LOP by going high up (7000ft+), WOT and then lean as much as you can. A little carb heat helps (caution: some carbs will freeze and even full carb heat will then not fix it!).

Last Edited by Snoopy at 15 Oct 18:45
always learning
LO__, Austria

@Dan thanks for the App recommendation, very nice!

always learning
LO__, Austria

igor wrote:

Am I understood correctly, that by leaning until roughness and then giving back 2-3 twists to enrich you should be in the ballpark of -50* F LOP EGT?

You can’t be sure about that. Onset of roughness isn’t caused by leaning as such and thus has no direct relation to EGT. It’s caused by small differences in mixture between cylinders. As power drops rapidly lean of peak EGT it is likely that these small differences will give noticeably different power from different cylinders and thus roughness. That’s why you can buy “calibrated” injector sets for fuel-injected engines to ensure that all cylinders get the same mixture. It is more difficult with carburetted engines.

ESKC (Uppsala/Sundbro), Sweden

Dan wrote:

Jim Petty has a fantastic little iOS app called AircraftPower

The App is just so good if you’re really interested in what your engine is doing. I used it since when I bought my plane, and for the next flight with two pilots on board have plans to understand and use it in flight. To see where I really am. We talked about this and believe that with some settings tricks we can spare another Gallon/hour on same speed.

igor wrote:

Am I understood correctly, that by leaning until roughness and then giving back 2-3 twists to enrich you should be in the ballpark of -50* F LOP EGT?

It’s impossible to say where you end with this trick. For example, on my engine, reducing to 2000 RPM I cannot really go LOP, as the EGT does not fall below peak upon leaning. When I set, say, 2500 RPM or more, I can perfectly lean down to 150°F LOP and have no roughness whatsoever (GAMIjectors installed). Another influencing factor is the output power set. For example, with my engine it’s not possible to fly far LOP during lower power like in a descent. I have to enrichen the mixture a bit, else it will run rough. And that’s all with the same engine, just different settings.

If you don’t have any precise instruments this “trick” is the best you can do, however. It should start running rough only in the region of peak EGT or maybe up to 100°F ROP. So this is more or less about where best economy is indicated in the POH. Just make sure that you stay on lower power outputs to not harm the engine, I’d say not more than 65% power, if you don’t have single-cylinder CHT. Maybe even less.

Germany
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