Jerry,
I don't think that 3" is nearly large enough.  You will probalby need

about 25 sq. in. of intake area (according to Fred Morino) for the oil
cooling.  The 3" is a really small duct.  Take a look at the following
numbers:

3" = 7.069
4" = 12.57
5" = 19.63
5.5" = 23.76
6" = 28.27

FWIW, I'm not flying yet.

Ken P.

Ken Powell
kenpowell@aristotle.net

Good point Ken. I missed that.

Paul Lamar

My original oil cooler location (Earl cooler) was within 12" of the
firewall
and with the initial 3" dia duct temps went to over 240F on first
flight.
Later and even with a better plenum and  5" dia duct cooling was
marginal.
Could have been the oil cooler or the location or a poor plenum, but I
did
not get effective oil cooling until I went back to the stock mazda oil
cooler and moved it up under the spinner.  FWIW

Ed Anderson

I am  skeptical about the need for intakes that are 25% of the surface
area of the rad or oil cooler.   According to that rule, the Mazda stock
oil cooler would require about 22 sq. in. inlet.   Inlets for  typical
radiators would have to be 100 sq in or more total.   Since there are
Mazda powered  RV  that are flying with  with the  stock cowl inlets (42
sq in total), the theory is having trouble with the facts.   ( Sam James
is producing RV cowls with round cooling inlets that are only 4"
diameter for the 0-320.   That is 26 sq in total inlet for an  0-320.
These work.)

  I have an alternative  inlet scheme for the oil cooler that  provides
more inlet area by dividing the intake plenum in half and feeding each
half from separate 3" inlets.  This is easy to do in my situation.   I
am planning to  use a similar design (two smaller belly scoops to a
divided plenum)  to feed air to the  fuselage radiator.      Jerry

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