Proper Leaning Technique - Cherokee 140

CC268

CC268

Final Approach
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CC268
I know this is probably going to open up a big box of worms as it seems to be a controversial topic for some. When I was doing my PPL (in a 1979 172N) I always leaned for taxi and did a full power run-up and leaned until I got a power drop in which I would then enrichen about 3 or 4 turns.

Anyways, now that I am an aircraft owner with my dad (1965 Cherokee 140) I want to treat the engine well. I have read Ted's threads over in the Maintenance Bay as well as many other articles online about engine maintenance and leaning techniques.

My airplane does have a CHT, EGT gauge (just a gauge with two needles, it isn't digital or anything) - I haven't even really looked at it yet to be honest as I never used one in my training.

I came across this article which I found to be pretty interesting. It says you should either run 100*F rich of peak or 20*F lean of peak. In fact this writer states that running 50* ROP is the worst thing you can do.

http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning-198162-1.html

Anyways, just wondering what your guys' thoughts are. Just trying to educate myself as best I can and take care of the engine.

Also...I haven't been leaning for taxi in this airplane and I have been running full rich on takeoff. I am thinking I ought to lean for taxi and then put it back to full rich for takeoff (unless I am at a higher elevation field of course).
 
Are you based at a high altitude airport? Max RPM at run-up is not appropriate in a 172N unless above 3000 DA. Leaning until the engine drops is a bit too much.

Cherokees seem to want it a bit richer.
 
With my 180 I lean very aggressive on the ground. If I tried to add full power at that point it would die.

Run up full rich and for take off full rich, I'm a flat lander.

Take off full rich and climb above 3k lean to max rpm.

Cruise flight lean to roughness and enrich slightly to smooth out. Or if I want a few more kts and burn a gph more I'll lean in cruise until max rpm.

I don't worry about LOP or ROP operation, I have no engine monitor. But I'm sure leaning until rough and then smoothing it out will likely put you in one of those ranges...
 
MAKG1 said:
Are you based at a high altitude airport? Max RPM at run-up is not appropriate in a 172N unless above 3000 DA. Leaning until the engine drops is a bit too much.

Cherokees seem to want it a bit richer.
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Airport elevation is roughly 1500', but DA is often over 3000'. Now that is is cooling down it will start to come down a bit. Okay thanks for the feedback, I have been running a bit rich anyways.
 
In my 140, I leaned aggressively on the ground (same as above) and then on level off, I leaned 100 rich of peak. You aren't going to do LoP on a Cherokee 140 (no fuel injection). I would lean again, if I climbed significantly.
 
ircphoenix said:
My 1970 Cherokee 140 says lean until rough, then enrichen slightly.

So that's exactly what I do.
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When I follow this approach in planes with fancy engine instrumentation it seems to get to the right point more or less all the time.
 
As above is what I do as well with most carbed engines, lean like crazy on the ground to help prevent fouling on the plugs. Full rich, unless DA is above about 5K, for TO. Climb up and lean. If I'm going high, 9-10K, I will pull a little on the red as I climb, then once in cruise use the gauges or rough then smooth for final setting.
 
Cool thanks for all the feedback guys!
 
John221us said:
In my 140, I leaned aggressively on the ground (same as above) and then on level off, I leaned 100 rich of peak. You aren't going to do LoP on a Cherokee 140 (no fuel injection). I would lean again, if I climbed significantly.
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This seems like a good method.
 
Years ago!! when I was taught not many had all these fancy analyzers. (PPL in 1974) So I learned the lean till rough, then smooth it out method. But I was also taught to monitor the oil temp very closely. That is the only gauge you have to tell you whats going on inside the engine. All the rest are external reading. Even today with all the fancy stuff, I watch oil temps very closely.
 
For takeoff above 5000' DA, I like to lean to max rpm, then richen a couple of twists.

As others have said, I wouldn't try running LOP at cruise with a carbureted engine. The good news is that with your plane, at cruise above 8000' DA, you can put the mixture anywhere you want and not hurt the engine with detonation. I like the "lean to roughness, then richen to smooth a little" approach.

I'm always fiddling with mixture at altitude (with my fuel-injected engine) to run a bit LOP and keep the cylinder head temps down and gain a bit of extra economy. Sometimes a 30-degree LOP setting will result in rough running initially, but it'll settle into smooth running after 10-15 seconds or so.
 
cfiiguy said:
Years ago!! when I was taught not many had all these fancy analyzers. (PPL in 1974) So I learned the lean till rough, then smooth it out method. But I was also taught to monitor the oil temp very closely. That is the only gauge you have to tell you whats going on inside the engine. All the rest are external reading. Even today with all the fancy stuff, I watch oil temps very closely.
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Yup, without A CHT/EGT, your stuck with leaning the old fashioned way. Pull the mix out till the RPM's peak, enrichen and monitor oil temps. It works, just not as precise.
 
I have an EGT in my Archer, it has a little adjustable reminder needle on it that was set when I bought the plane. Sure enough the point at which it's a bit too lean and starts to run rough is slightly hotter than that needle. For me the EGT really ends up being a nice visual indication of how close I am to ideally leaned out but engine feel remains primary.
 
Whenever I was flying a 140 which was in the late sixties early 70's always leaned on taxi,then full power for takeoff,then lean to roughness ,enrich till running smooth. Also leaned on high density altitude.
 
Another approach which I have read but never tried is similar to the lean til rough, then enrichen til smooth is put in carb heat, lean til rough, remove carb heat. Supposedly same end result. Anyone know more about this method?
 
Graueradler said:
Another approach which I have read but never tried is similar to the lean til rough, then enrichen til smooth is put in carb heat, lean til rough, remove carb heat. Supposedly same end result. Anyone know more about this method?
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Your not supposed to use carb heat on a Cherokee unless you suspect icing, unlike a Cessna. Supposedly it can cause detonation.
 
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