As you can see the pressure difference across the right radiator
is 5.11 - 3.61 is only 1.5 inches of water or about .055 psi
which is hardly enough to generate a gentle evening breeze.
In effect this radiator is not functioning. Well hardly at all.

I'd say the 1.5" drop across Tracy's radiator gives a lot more than a

gentle

breeze.  That's enough pressure to produce significant flow, especially
through a fairly open core as I believe the air conditioning cores are.
That's enough for about 2000 cfm through my 16 fins/in radiator.  That's

a

pretty strong wind - or I guess one could say - it's a lot of hot air.

I've also done some measurements on my custom oil cooler.  More on that
later.

Al Gietzen

As I recall Tracy's AC cores are 3.5 inches thick and not 2.5. As I also

recall,

but I could be wrong, the flow per square inch is inversely proportional
to the square of the thickness. 1/6.25 = .16 while 1/12.25 = .081 or
about half the flow per square inch of frontal are. Due to the thicker

core.

Now as to the volume or CFM of air going through you must realize
Tracy's rads are only 10 by 9 inches for a frontal area of 90 square

inches

while your rad is 184 square inches or twice the total flow for the same

pressure

drop if the thicknesses were the same which they are not. They are much

thicker.

Also the fin spacing looks much closer on the AC cores than it does on a

real water

cooling radiator. My guess is Tracy's AC heat exchanger cores are flowing

one

quarter of the air that your rads are at the same pressure drop.

That could be right.  There is nothing optimum about Tracy's core, or the
inlet ducting; but I guess the important thing is that it works.

Al Gietzen

It sort of works. Tracy complains about the oil temp getting too high
when we climb for too long or make some top speed runs. Tracy lives
in flat country. It is never necessary to climb out at max angle.
In fact it is rarely necessary to climb over 500 feet but he does it
slowly anyway when he goes on a long cross country.

With one simple cowl flap down under the engine I think it would 
work a lot better and he could make those inlet holes a lot smaller. 
Tracy is not convinced. He was mumbling something about getting the air warmer
by keeping it in the AC core longer or something like that. :-)>
He also does not think those big inlet holes are hurting him on drag either.
His argument there is external diffusion. Top speed is about 205 MPH
but I think with some cooling drag improvements it might reach
215 MPH with the same power. We have sort of agreed to 
disagree :-) I left the water manometer with him and I hope he finds 
time to make some improvements and do some more tests. 

BTW the water manometer could measure the flow through the
rad if you set up some pito tubes in back of the rads.

Paul Lamar
 
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