And, again, in terms of reliability as long as the absolute CHT value is low enough to cool the exhaust valve adequately nothing matters too much on a carburated low speed plane except that when leaned (even by ear and feel) you’ll have just enough fuel to avoid roughness/misfire on the leanest cylinder… and will as a result save fuel to whatever degree. Training and club aircraft with reasonable cooling and Lycoming engines have been abused mercilessly for decades minus EGT gauges and in some cases CHT instrumentation, and unless its leaned at over 75% power with high CHT on all cylinders as a result I don’t think much goes wrong.
You can make leaning into a PhD thesis if you like, as you might justifiably do with a tightly cowled fast plane on a long range flight, but on a well cooled low speed ‘club’ type, as per the original post, making leaning non-critical for reliability was figured out decades ago during development: adequate air cooling was designed in. Individual cylinder EGT and CHT instrumentation, matched injectors etc are for minimizing high fuel consumption in cruise and preserving the cylinders in climb…. on fast planes, gulping fuel quickly enough to worry you, with marginal, low drag cylinder cooling.
I still have some reservations without any means of monitoring. In the rental enviroment even if all of these elements are understood by the rental pilots do pilots forget the mixture having set it? I fully appreciate even owner pilot can do this, but my point is that while it might not be for technically the correct reasons I have a lot of symphathy with the engineer in the OP efffectively trying to encourage the “club pilots” to run the engine rich of lean. Maybe I am being overly cautious? However pulling cylinders is a costly business.
I wanted to know this and I figured who knows better than the Manufacturer and they were nice enough to write it down in the Lycoming Operator’s Manual on Page 3-7. I fly a normal aspirated IO360A1B in my Lake:
Leaning to Exhaust Gas Temperature Gage:
(1) Maximum Power Cruise (approximately 75% power) – Never lean beyond 150°F on rich side of peak EGT unless aircraft operator’s manual shows otherwise. Monitor cylinder head temperature.
(2) Best Economy Cruise (approximately 75% power and below) – Operate at peak EGT.
It says for leaning without EGT or flowmeter to lean until power loss is noted (fuel injected engines) or to lean until roughness is observed (carbureted engines) and then enrich until either power is regained (fuel injected) or engine runs smooth (carbureted).
Fuji_Abound wrote:
Airborne_Again – what monitors do you have in the Club aircraft for cylinder and exhaust gas temepratures?
One of them (Cessna 172S) has digital EGT and CHT indicators for each cylinder as well as a digital FF indicator (part of the G1000 package). The other two (Cessna 172R and PA28-181) have a single analogue EGT indicator – the C172R additionally an analogue FF indicator. We have been discussing installing digital engine monitors in all aircraft but then the average club member must learn how to use them otherwise not much is gained.
Airborne_Again – well that is very good news and some well fitted out aircraft. With that ability then I would agree with others you have the means to operate the engines “properly” but as you rightly say it is now down to education.
I learned to lean in cruise until it starts running rough, then make it richer until it runs smooth. I still use that method, works every time 
Also, lean on the ground the same way, just remember full rich at take off.
Re full rich for takeoff, for high altitude takeoffs you generally lean just rich of roughness before takeoff, and that is often in accordance with the manual on the basis that takeoff power is often restricted by altitude to below 75%. But there is a little problem if takeoff power is determined to be 80%…. In that situation I lean the same way for takeoff, check and potentially adjust EGT on the climb and monitor CHT to make sure it’s in the normal range.
A bigger concern for me at that point is if the mixture is too rich, the feeling of climbing at (say) 300 rpm with a rich misfire is not pleasant and when the engine is running not so smoothly there is (regardless of logic) an emotional resistance to pulling the mixture knob leaner! In a situation where one may have set mixture poorly before takeoff, when climbing out near terrain, it takes a certain level of self control to lean until the engine runs rough then slightly richer.
@LeSving: that is how I have learned it as well. The article mentioned above by @Rwy20 is a very good article and I am glad he posted it.
When flying the SR22T with Garmin Perspective, I have all the engine parameters on my screen.
When flying the Piper Archer 3, I only have the EGT. So, from the article @Rwy20 posted, I take that leaning to peak EGT is good, but that you should not then move the mixture “just a little” richer than that as that will bring you to the highest possible CHT temps.
Also, the rough running engine when you lean is just an indication of one cylinder running different from the others and not directly a sign that the engine is being “starved” of fuel.
So, it seems to me that in the Archer, it might be worth to look at EGT peak as your aim as it will be just on the lean side of peak CHT. Right?
So, which EGT is hotter, 50 ROP or 50 LOP? Duh, that is like saying 1 out of 10 people are in the top 10 percent. Ten percent of what?
At 50 ROP, the CHT will be the hottest. At 50 LOP, the CHT will be up to 30 F lower.
I don’t rent and have to pay my own fuel and maintenance bills. I just set the fuel flow to 12.5 GPH on my IO520BA engine. That provides me with about 65% power, almost totally independent of the MP and RPM. I don’t use an engine analyzer or EGT for the purposes of leaning, it is a waste of time. I merely set fuel flow. I use the engine analyzer for analyzing problems, like when the engine does not run smoothly.
My response to those who take the advice of mechanics on how to operate the engine, I reply, does the concert pianist check with the piano tuner on how to play the piece. I don’t think so.
NCYankee wrote:
My response to those who take the advice of mechanics on how to operate the engine, …
Listening to the mechanics is not a bad thing. They know what tends to break easily and why it breaks. I talk a lot with ours (some of them have a PPL…) and as long as it does not contradict the POH try to follow their guidance.
