Putting that back panel in there reduced the velocity of
the air going through that portion of the radiator.
>From about 40 MPH out of the back side of the rad to 
about 32 MPH out of the back side with an airspeed
of 74 MPH.

Here is a shot showing both the static pressure taps
and the velocity probes. Static pressure built up in the exit
chamber to impede the flow.

Anything within ten inches of the back side of the rad
is going to cut the flow. Keep the rad as far away
from objects as you can. The closer the object such as 
an oil pan, muffler or engine block the worse the flow interruption 
and the bigger the rad required. 

The easiest thing to do full scale  is
just measure the static pressures as once you have a good
inlet duct there is little you can do to enhance the flow
through a given radiator.

For the next test I will remove the back panel and change
the inlet area to see what effect that has on rad flow.

Paul Lamar
 
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