[KyleTownsend]

WOOPS! In my previous post, item (c) should have said "operate at peak EGT" not "operate at peak CHT".

Now, on to my real question.

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.

Taking the manufacturers "side" for a moment, I believe that we all agree that:

(1) at the time most of these airplanes were built, multi-probe engine monitors were either not available or were prohibitively expensive (they are still pretty expensive); and

(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).

Now, here is the part that I "don't get." Cessna has the charts, GAMI has the (even better) charts. If I am reading them correctly, then operating by the manufacturers settings at 75% power leads to the highest possible CHT's for that power setting. They just aren't going to get any higher, no matter what you do (o, if you want to split hairs, they can't get more than a few degrees higher, since true peak CHT is more like 40 DROP EGT).

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?

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).

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).

But for argument's sake, lets say I have GAMI's but my engine monitor died or whatever, so I'm having to rely on the factory gauges.

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

Of course, the "catch" is, that if I leaned to peak EGT, or leaner, then I would not still be making 75% power. I would be making some lesser amount. But if I am OK with making this lesser amount of power, I really don't see how this could possibly hurt anything.

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).

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.

So, I can see why this would be a no-no.

However, I can't see why I shouldn't lean as much as I want to from the factory 75% setting, provided that I don't do the "power recovery" step.

Am I thinking right, or not?