Why is LOP (lean of peak) controversial?

Doug wrote:
: One thing no one has mentioned is LOP may not be possible with
: carbureted engines. The flows to each cylinder just aren't consistent
: enough to make it work. Also you really need CHT and EGT guage on each
: cylinder to do it right. The problem with LOP, isn't running LOP, its
: that you are running peak and THINKING you are running LOP. The same
: could be said of running rich of peak too. Running AT peak is really
: only a problem at higher power settings. So most of this LOP stuff is
: really for turbocharged fuel injected engines. I said MOST. Some people
: with just fuel injection use LOP and a FEW at least claim to use it
: with carburetion.

: LOP works, but I think you have to really know what you are doing and
: have the right equipment. But if you are running at 65% power or below,
: it doesn't hurt to try it, no matter what sort of equipment you have
: (unless of course you dont even have a mixture knob :-))

I guess that's what I was trying to say. I'm assuming that most people
reading the thread know that carb'd engines (particularly 6's) generally have too poor
fuel/air distribution between the cylinders to run LOP.

I do know that I am running about half of my cylinders slightly LOP and about
half AT peak. Although the EGT is higher than LOP, the CHT is *lower*, and thus
should have cooler exhaust valves (or at least about the same). That's also why I
tend to limit myself to 65-70% at most. A little safety margin. Besides for my bird
(PA-28), the airframe doesn't buy much speed increase from 65-75% on a 180hp engine.
It's not worth the extra fuel burn for the additional 5 mph or so.

Again, the *at peak* operating condition is mentioned in one of the Lycoming
publications as the "best economy cruise" setting and is considered acceptable.

-Cory

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* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
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