Leaning with fixed pitch and no egt

[Caramon13]

From Lycoming:

For a given power setting, best economy mixture provides the most miles per gallon. Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM. Some engine power and airspeed must be sacrificed to gain a best economy mixture setting

Reference here.

 

[cowman]

I have a good deal of experience in an Archer II which I don't think should be significantly different than the III.

The mixture lever on mine wouldn't have much of an apparent effect until you pulled it about halfway down. So when I leaned I would always start out pulling it about halfway down straight away, then move it leaner in small increments, waiting a moment inbetween until I either saw peak EGT(which you can't do) or the engine started to feel rough, then move it a tiny increment back rich. Response from leaning isn't quite instant so it's important to wait a moment to see the results of your change, just a couple seconds but if you just keep moving it without pause to see the result you'll go way too lean.

Your dead zone on the mixture lever may vary but doing what I described above should result in satisfactory leaning. If you lean too far, you can always enrichen so it's not a huge deal

 

[schmookeeg]

No need to rush; it's a process, not an event. Get in the habit of adjusting it slowly, or one day you'll pull it too far too fast.

pull too far, too fast... and then... what? he will need to push it back in?

 

[Salty]

If you pull it too fast you can’t properly determine peak.

 

[schmookeeg]

If you pull it too fast you can’t properly determine peak.

Slow EGT probes suck.

Was OP asking how to find peak, or just how to lean for cruise? I haven't met many CFIs that are concerned with the LOP/ROP religion, or fuel efficiency.

 

[iflyvfr]

Once in cruise if I want to go fast I'll lean again to max RPM or to save a bit I'll lean until the engine stumbles then enrich it just enough to make it smooth. Ill do the big pull kinda fast but I also know about where its gonna be anyway. Well and I do go full rich for landing though it's not needed but less to do if a go around is needed.

It's exactly the same in my C-172, except for the go fast part.

 

[Jim K]

Slow EGT probes suck.

Was OP asking how to find peak, or just how to lean for cruise? I haven't met many CFIs that are concerned with the LOP/ROP religion, or fuel efficiency.

Mainly just if my procedure was correct. Fuel mileage isn't a huge concern, just don't want to foul the plugs, and in a more general sense not prematurely wear the engine. I do intend to purchase my own plane in 3-5 years, so I want to ingrain good habits now.

 

[1RTK1]

Love those guys but I suspect the "big pull" is less of an issue than they make it. If the concern is high CHTs, at least in the airplanes I have flown, I have not seen temps rise to the danger level in the ordinary course of the leaning process. That said, especially on high performance engines, I kind of like the idea of learning where the ballpark setting is manually. Just makes the whole thing more efficient.

I think the big fast pull was more of a thought for turbo’d engines where you would spend to much time in the red box pulling slow possibly causing detonation and preignition.

 

[simtech]

It's exactly the same in my C-172, except for the go fast part.

Well...fast for a Cherokee haha I get 120kts at 8k leaned to roughness and enriched to smooth.

 

[midlifeflyer]

I think the big fast pull was more of a thought for turbo’d engines where you would spend to much time in the red box pulling slow possibly causing detonation and preignition.

It may be more of an issue with a turbo, but even with non-turbos it is about spending too much time there.