From: "George Braly" <gwbraly@gami.com>

Dan,

While you cannot identify the "guru" from either L or C to which you
attribute the comment about LOP operation,  let me help out and identify one
such legitimate "guru".

>From 1996 to 1999, I, personally, spent a LOT of time with the former V.P.
of Engineering for TCM.

He was at TCM for 40 years, and was the VP engineering for the last 7 or 8
years he was there, before he retired.

He is widely regarded as the most knowledgeable general aviation piston
engine engineer in the last 50 years.

His name was Carl Goulet. He died a couple of years back.  He so impressed
me that I named a whole facility after him as a memorial.  See
www.engineteststand.com.

Carl made no bones about it.  

That comment was made to me in the spring of 1997 after I had just
demonstrated the operation of one of his engines at 85% of rated power while
90degrees F lean of peak.

His direct response I offer as a quote:  "Leaner is cleaner.  Leaner is
cooler.  Cleaner and cooler are better for the engine."
 
He said this in the context of a discussion of the TSIO-520BE engine - -
which, by the way, is ONLY authorized to be run lean of peak.  High power
rich of peak cruise operations are not authorized by the OEM.

Those engines use the same exhaust valve as every other big bore TCM engine.
Their exhaust valves routinely go to TBO - - but only when the engines are,
in fact, meticulously run ONLY lean of peak by the owners.

The engineering text book defined concentration of O2 in a LOP exhaust
stream is about 1.5%.   The air in the hangar is about 19%.

The story you heard from the unknown and un-identified L? or C? "guru" is
typical of many uninformed pieces of information that come out of both L &
C.

If you find the people that really know the engineering,  they will tell you
that LOP operations are always better for the engine.

If you get a chance, you might consider coming to one of the Advanced Pilot
Seminars on engine management.  You can see from the real time combustion
data from the test stand the difference in the combustion environment
between ROP and LOP mixtures.

The CW-3350 engines frequently went to 3600 hours TBO - - ALL of the cruise
portion of their operation was lean of peak.  They accumulated about 300-500
million engine operating hours lean of peak.  You cannot find a single
reference in the SAE literature that attributes any premature valve failure
to the presence of oxygen in the exhaust stream for those valves operated in
that environment for over 20 years during the heart of the piston powered
aircraft era.

Regards,  George Braly