"Bass, Jerry" wrote:

Thanks, if I modify the duct as you suggest, will the air move

forward,

towards the front of the cooler?  Some who have looked at it say the

air

only goes toward the rear.  I have enlarged the air inlet from 2 sq.

in. to

8 sq. in.  and blocked the bypass to not bypass with no improvement

Jerry Bass

That's why you need to skinny the back of the duct down a bit.
A straight wedge shape works fairly well but not as well as duct
that is thinned down near the back. Get one of those digital wind
meters and pump some air into the duct with a furnace blower.
Use the wind meter to survey the air velocity coming out of the
back side of the oil cooler. Here is my test set up for radiators.

Paul Lamar

Ken Powell wrote:

I'm not sure that I remember the original post.  If Jerry is only
using an 8 sq in opening for his oil cooler then the oil probably will
not cool properly.  We all seem to agree that the oil will accept 1/3
of the head of the rotary - Fred Morino recommends a total radiator
inlet size for both the coolant and the oil to be between 66 and
81 sq in.  Based on Fred's estimates we need an oil cooler opening
of at least 22 sq in.  I think we might get away with less because
the Delta T of the oil will be higher since the oil temp is higher than
the coolant temp.  Every time I read Fred's research paper I seem to
learn something new.  This is my best guess based on Fred's research.

Ken Powell

Ed Anderson wrote:

I am in agreement with Ken.  My oil cooler opening (2"x10" = 22 sq inches)
up under the spinner is adequate for a NA 13B producing around 180 HP. 8 sq
inches just does not strike me as being nearly enough.   My radiator
openings are closer to 24 sq inch each for a grand total of 70 sq inches for
both radiators and oil cooler. This appears to be in agreement with Fred's
findings.

  Typical temps are 190 F Oil and 180 F coolant during summer months.  Will
occasionally get up to 200F on hot day climb out.

Ed Anderson

I don't disagree :-) Just for the record you still need a good duct
shape. With the right shape you can minimize the opening area and cut the 
cooling drag.

Paul lamar

 
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