Joseph M Berki wrote:

Hi Paul,
        I am looking again at the cooling system for the Limo.  I know you are a
fan of the straight wedge ducts with a thin radiator.  What would result if
several thick evaporator cores where placed in a wedge duct fed by an
expanding duct / scoop?  My rationale is that if velocity is traded for
pressure you could improve flow through the thick cores.  I keep thinking
about the P51 rad that was 7 or 9" thick.  I know it is twice as fast but
evap cores are 3.5" thick.  An augmenter would  also be used to push air
out of the cowl.  How do you determine the curve in the floor of the wedge
duct?  It is not K&W?  Thanks for any help

Joe Berki
Limo EZ

Couple of problems with the evap cores. Number one they are too thick
so air flow, hence heat transfer  at climb speeds would be limited. 
If your diffuser STOPS the air you still only have .2 psi at 100 MPH.
Real world diffusers are lucky to see .8 times that or .16 psi. 

Number two the internal passages are not optimized for engine coolant. The 
only thing they have going for them is cheap if you buy them in 
a junk yard. An all aluminum  two inch thick car racing rad can be 
had for $200.

The P51 core was 11 inches thick but it had 16 times the pressure
at 400 MPH. Also it mainly took off in England where the temp rarely
gets over 65 F :) Also the P51 duct was plenty long enough for a
K&M bell shaped diffuser however it did not use that shape until
near the end.

A wedge shaped diffuser will work with any core thickness provided
you have enough pressure to jam air through it.

An exhaust ejector will up the pressure drop across the diffuser
no doubt about it. Might be enough. Then again it might not.
You could carry around a water dribble systems for hot days like
Tracy does :)

I know you don't have the necessary width between the motor mounts
to use a conventional rad mounted on the firewall like that OSH Power 
Sport Velocity. About your only hope is a horizontal rad under the engine
with an ejector. The ejector shown in this 3D needs to be wider and longer.
it could transition from a rectangular opening with two exhaust pipes
in front to a round opening at the prop for a more esthetic appearance.

Keep the duct feeding the wedge constant area.

Paul Lamar
 
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