[Walter Atkinson]

Kyle:

It seems to me that you're gaining a pretty good hold on the concepts. Some points to further your understanding:

**I don't actually think that the LOP guys and the manufacturers are as far apart as they appear. They certainly aren't that far apart on their data.**

Actually, there is no argument at all on the data. None. Period. It all agrees 100% because, as Sir Isaac Newton said, "The physics are everywhere the same."

**(2) without these engine monitors, there is no better alternative than following the manufacturers recommended power and mixture settings, provided we keep an eye on the CHT's (by running them at 400 degrees or less).**

That's close, but not altogether precise. Keeping CHT's below 400 is a good guide but it does not address ICPs completely, but it's difficult to be too argumentative with that statement. It's pretty close.

You comments about the charts are correct. The Cessna and GAMI charts are in agreement because the physics are, indeed, everywhere the same.

**If this is true, and if "everybody" knows that operating at peak EGT is actually going to be cooler than operating at 50 DROP, then why does the POH say you shouldn't lean to peak EGT above 65% power?**

Because an engineer didn't write the POH! I, too, would like to see a scientific explanation for that statement. I know of none. OTOH, be aware that the common recommendation not to lean above 75% power is an attempt to keep the pilot from operating inside what we later termed the Red Box. It was an admonition by the OEM that assumed that the pilot was not knowledgeable and had little instrumentation--which in many cases isn't all that bad of an assumption!

**Correct me if I am wrong, but I can's see anything wrong with setting MP and RPM for 75% power, then leaning to peak egt and leaving it there (instead of enrichening to 50 DROP).**

Our research indicates that peak EGT is not quite lean enough at 75% power to keep the ICPs low enough to be in harmony with longevity concerns. You are absolutely correct that it is a better choice than 50dF ROP. I'd say peak is "less bad" at 75% power. <g>

**Extending this argument further, I don't see any reason that I couldn't continue to lean the engine until I was running at 50 DLOP (assuming that the engine would run smoothly at this point, which it probably wouldn't without gami's).**

That is 100% in harmony with all of the known physics.

**I absolutely don't see how this would hurt anything.**

It won't. It's actually better.

**And this is where I guess the "kicker" is. In order to perform LOP operations AT HIGHER POWER SETTINGS (I am guessing settings where the real power exceeds around 65 to 70 percent), it is necessary to move the manifold pressure and/or RPM controls to a position HIGHER than the factory recommended settings for 75% power operation (the "power recovery" step).**

Correct. You have to get the mass airflow up so you can put the fuel to it. I currently, routinely operate at about 60dF LOP, 85-90% power in cruise. The engine loves it..... and I go faster on lower FF than if I were making 75% power ROP.

**If I do this (eg: by advancing MP until the airspeed is what it was before I started leaning) and I DON'T have an engine monitor, then it is possible that an individual cylinder could be running at some power setting greater than "book 75%" because of unbalanced fuel flows.**

Right... but... if it's running smooth LOP, it MUST have balanced FFs. <g> In that case, you don't need an engine monitor to run LOP.

Duzzat make sense? <g>