Leaning Procedure for a Carbureted 182

I fly a C182P with O470S. Recently read the engine management and leaning
articles on AVWEB prior to a long (1200NM) cross country. I have a 6
cylinder analyzer with CHT and EGT for each cylinder. Cruising at 7500ft I
would lean to about 75-100 ROP on the first cylinder to peak. I would have a
large descrepancy between EGT temps between the cylinders due to uneven
distribution of fuel air mixture in the O470S. I then tried a trick
mentioned in those articles. I would back off the throttle until MP just
noticably fell (about 1/4 inch MP). After a couple of minutes the EGT's were
all within 25 degrees of each other. The idea put forward in the article was
that by partially closing the throttle the turbulence created resulted in
more even distribution of fuel. Don't know if there is any rational basis of
this but seemed to work in my plane.

Howard

Howard,

After a couple of minutes the EGT's were
all within 25 degrees of each other.


Just to make something clear about a common misunderstanding he The
goal is NOT to have the EGTs equal. The goal is to have the EGTs in
equal distance from their respective peak. The absolute EGT value
doesn't matter.

--
Thomas Borchert (EDDH)

A couple of observations. If you are running rich of peak, you want ALL
they cylinders to be rich of peak and you use the leanest, highest temp
cylinder as your guide. If you are running lean of peak, you want all
the cylinders to be lean of peak, and you use the RICHEST, highest temp
cylinder as your guide. One can see why it is good to have all they
cylinders close to each other. This is what the Gami's do.

As for carb heat. If you put on the carb heat you introduce hot air,
which is less dense. You have just richened the mixture.

As for throttle pull back. If you lean to roughness, then pull back the
throttle, you have just richened the mixture.

There is no magic. You can safely operate at high power setting rich of
peak or lean of peak. To operate lean of peak you need (or want)
EGT/CHT monitoring of all cylinders, fuel injection, Gamis and fuel
flow monitoring to REALLY do it right. You MIGHT be able to operate
lean of peak successfully with a carbureted engine, but most can't
because of uneven air and fuel distribution.

If you operate at about 50% power you can run as lean as you want
because you won't be generating enough heat to do any damage. 65% power
takes 50 degrees rich (or lean), 75% takes 100 degrees rich (or lean),
85% 150 degrees rich (or lean) etc.