I have a 360 with a 200 HP engine.  My oil cooler is a 13 row cooler and my
baffling is as tight as the part of a duck that is usually described as
watertight.

I have plenty of exit area at the rear of the cowling, but as my cowl is not
stock and the fuel injection unit is forward facing from the side of the
pan, there is no need for a "trough" in the cowl.  The rear of the cowling
is therefore level with the bottom of the firewall.  I did all the
housekeeping items, gauge check, vernitherm check,  verification of all
baffling and manufacture of a proper plenum chamber on the cooler before I
embarked on the following pilgrimage.

I started off with the cooler on the firewall fed through a 3" scat hose
from a NACA duct on the RH side of the lower cowling.  Oil was too hot.  I
opened a 3" hole in the RH rear baffle and fed the cooler from there.  Not
sufficient improvement!  So I made a large Y and fed the cooler from both
the NACA duct and the rear baffle.  Here I think one source fought the other
and the oil was still too hot.  Next step was to put vents in the bottom of
the bottom cowling as per a recommendation in the Lancair newsletter.
Better but not good enough. I removed the Y and increased the exit from the
NACA duct to 4",  still not satisfactory.  So I fitted vortex generators as
per the recommendation of another list member.  Much better but still would
not provide consistent cooling for multiple touch and go. At this point I
gave up on the NACA duct and blanked it off.

I increased the size of the cowling air intake by 50% and built ramps inside
the  cowling top to smooth the air entering the cowling and prevent
turbulence.  The cooler went on the rear RH baffle.  Bingo! My only problem
now will be to build restricter plugs for the winter to keep the engine and
oil warm enough.

I do not know neither do I care particularly or even notice what this has
done to my drag and/or speed.  I can point the nose skyward on the hottest
day and climb, climb climb without worrying about the temperatures.  Engines
are too expensive to mistreat.  They are also fundamental to your health.

If you go to the RV web site there is information available on the best way
to get good cooling.  I believe the smoothing of the turbulent entry flow is
a big factor in getting air through the engine and cooler.

There are many ways of killing the proverbial pig, this worked for me.

Ian Crowe
C-FKRO 85 hours and counting