Dan wrote:
IIRC @eurogaguest1980 was doing some testing with such a device, any feedback?
I have not finished installing my AF sensor – requires a bung welded to the exhaust and I’ve been too lazy to do it. Also, after getting more and more experience with the engine, I feel pretty comfortable leaning it in climb just by knowing some FF numbers, and then when in cruise at altitude, I just lean until it stumbles and enrichen a bit.
ch.ess wrote:
Rather than using the airplane manufacturers’ recommendations, I would use the engine manfacturer as the go-to expert. (Different to cars and motorcycles, airplane manufacturers are not engine experts, but depend on the three established players there)
And Lycoming’s recommendation for leaning (shortened) pull back the mixture lever until the engine runs rough, then enrichen a little so it runs smooth again For my IO540 that comes very close to Mike’s method.
Mfg. manuals nad recommendations for order Conti and Lyco engines are mess.
It is because it was written by old time where engine instrumentation and knowledge was much lower than now and it’s perhaps too much problems and afford for them to change it now (its certified). For them it’s better to leave it as it is. On other hand, more killed engines, more money.
When they was writing op manual for lyco 360 noone had idea about full engine monitors, gami spread, peaks etc.
I was expecting some novel discovery about what could harm the engine if you use EGT as a reference. Maybe not as the only reference, but it is still useful.
I started to think of it the other way round long time ago. I have an app on my tablet called “AircraftPower”, it calculates power for I’d say any aircraft engine for given RPM and MP values. So for example I typically take around 45% power in cruise, that translates to about 9 Gal/h. So I adjust RPM to 2000 in my case and MP and FF accordingly, depending on altitude, but still monitor EGT meter to verify that I’m not too far away from peak EGT. In my experience this takes a bit until optimal setting is found, where a bit off can easily be 1 Gal more FF (interestingly enough it’s never less 
less translates to rough engine run in a millimeter of the red knob) This results in a reasonable cruise speed of close to 150 true airspeed in my case. I have a penalty because I typically fly heavy. Initially, when close to MTOW, it’s only 145 knots while during cruise it gets faster.
@Mooney_Driver By the way, I still climb on 25 squared and can see nothing wrong with it. It’s about 75% power on my engine (at sea level) and that’s my typical climb power. I only choose more if it’s necessary, for takeoff or ice avoidance.
Mike is rarely actually wrong but in
he is right on best power but not really right on best economy which is achieved around 25F LOP, which is as near as dammit peak EGT.
I wrote some notes on this years ago here. Peak EGT is just fine for cruise – except at high altitudes where you need best power. Just make sure there is plenty of airflow coming in and flowing past the exhaust otherwise stainless steel gets a “bit soft” 
If TCM is to be believed, then the best economy, i.e. the lowest BSFC, is achieved somewhere around 50-60 F LOP (obviously these measurements have been made at 25/25, which is a rather high, low-level, power setting in an IO-550, but I wouldn’t think this changes with other power settings.
Sure, the efficiency difference between peak and 50-60 LOP is likely small, but it seems to exist. And when you need the power, than you obivously have to fly richer. But when I have the option, I tend to fly 50 LOP. 50 degrees lower EGTs are likely also a little bit better for the exhaust valves.
It changes with rpm. At lean mixtures, lower rpm eg 2200 produces a small second order gain.
Lower rpm also reduces pumping losses.
That procedure where one leans for the onset of roughness and then enriches a little is actually pretty good, where there is no engine monitor.
In “best power” the power curve vs fuel flow has a maximum, so fuel flow for best power exist
For “best economy” one needs to tack his decrease in aispeed as both speed and power drops when LOP down to zero, it’s hard to come up with a number but I would say 30deg LOP is best economy that keeps one closer to peakEGT speeds under that power & speed decays too much
ch.ess wrote:
Rather than using the airplane manufacturers’ recommendations, I would use the engine manfacturer as the go-to expert.
Remember that the airframe manufacturer’s information about how to operate the engine in that type prevails over the engine manufacturer’s information Note that the airplane POH is required to be carried aboard, but not the engine operating instructions – which pilots rarely encounter. And, the airframe manufacturer knows (and have tested) the instrumentation between airplane and engine (EGT probe placement, for example), so they may have information on indications and values which the engine manufacturer does not have for that particular engine installation.
In times past, at ASTM meetings, I would seek out and chat with Ceasar Gonzalez, who, at the time, was Cessna’s engine installation expert. He told me of flying he did in Cessna twins where they had severely damaged an engine during testing, and come home on the other. In brief, Ceasar told me that he was opposed to LoP, or peak operation, as he had damaged too many engines testing in that regime, he disliked 100LL, but understood it was a necessary compromise fuel, and he was a proponent of Mogas use, when correctly used. That’s why Cessna has not come out against MOGAS use in their planes, other than MOGAS containing alcohol. He owned a 150M, and flew it on MOGAS at the time.
Mooney_Driver By the way, I still climb on 25 squared and can see nothing wrong with it. It’s about 75% power on my engine (at sea level) and that’s my typical climb power. I only choose more if it’s necessary, for takeoff or ice avoidance.
So do I, because the AFM tells me to do just that. There certainly is nothing wrong with it, particularly if it is set in the AFM as the normal climb procedure.
Several high profile engine folks like John Deakin and also Bob Kromer (Mooney) did state however, that most engines could easily keep on take off power for the whole climb and some AFMs actually use those values for certain performance tables, some in contradiction to the procedure part which recommends a specific climb power. The important thing particularly for planning is to make sure what the tables refer to.
And if there is no limits indicated by the AFM, in certain situations where maximum climb is required or desirable, it is noteworthy that take off power will offer increased climb performance without risking engine damage as long as temperatures are observed.
If you don’t want to use your EGT for leaning for whatever reason – you may use your fuel flow indicator (if you are sure it works ok) with the following formula:
Normally aspirated engines with compression 1:8,5
Calculate gal/hr x 14,9 = HP roughly.
So to set 55% of pwr on 200hp engine – set correct MP and RPM acc to your table and set fuel flow to about 7,4 gal/hr.
Turbocharged engines with compression 1:7,5 –
Use 13,7 factor.
That value will put you just about peak egt, so use it only below about 70% pwr and lower unless you have good engine monitor and low gami spread.
