Tracy has argued that all your cooling air comes in
at 200mph, then has to slow down to almost 0mph to go through the radiator,
then accelerate back to 200mph again. All that work being done on the air
costs you -- it's drag. So he says that you want to put the minimum
amount of air through the radiator.

I don't know whether its significant or not, but a
couple of secondary effects occur to me...

1. If the air at the radiator is compressed, it will
be able to carry more heat away per cubic metre. So you want to maximise
the air pressure at the radiator. But compressing air heats it.

2. Heating the air as it comes through the radiator
will cause it to expand, and therefore produce thrust, which might be
useful in accelerating the air back up to the 200mph exit speed. I vaguely
recall that the P51's cooling system produced some thrust.

Frank.