Hi Listers

I feel for throwing in my 2 cents worth.
It appears to me that most participants in the discussion, focus on air
inlet to the oil cooler.
In my opinion the main point to get any heat transfere is air flow.
Air flow is a function of pressure differential.
If you do not have sufficient pressure differentian between 'front' and
'back' side of the oil cooler, you will not get sufficient air flow, to
take the heat out of the oil.

Having the oil cooler sitting in front of no 2 cylinder (on a 4 cyl eng) is
a good thing - if the inlet air is not stallet due to turbulence or lack of
trumpet function in the start of the plenum chamber. NACA ducts on the
cowling are another good solution - if they are not placed where
aerodynamics makes a low pressure at the location of the duct intake.

Not only do one have to ensure there is a high pressure on the air inlet
side, but you also have to ensure there is not a back pressure on the
outlet side of the cooler.

When cooling air for the engine enters the plenum chamber, usually above
the cylinders, it builds a pressure, to force the air down and around the
cylinders. Hereby the air is heated and expands, and if the volume or the
exit of the room below the cylinder is insufficient, it will build up a
back pressure. If the pressure in the area below the cylinders are too high
to make a positive pressure differential between the sides of the oil
cooler, it doesn't help you have got access to all the air in the sky, if
there is no force to move it through you cooler.

Usually the area of the cooling air outlet, should be many times the area
of the air inlet, a) to give sufficient cooling, b) not to buil up too much
cooling drag.
Please bear with my poor/unusual english, as it is not my mothertongue.


Regards
Villi H. Seemann
Senior Engineer
Infrastructure Network
Phone  (+45) 3333 2101
FAX      (+45) 3333 1130
CellPhn (+45)2220 7690