Ram Air--(higher pressure)
Is at the inlet --
not thru the inlet.
engine cooling requires that the air flow thru the fins -not over the heat bubble that is generated by the engine.
The question that needs complete addressing is not resolved by restating formula
How , can the model builder , best cause this air to cool the engine?
Does the ram air do the cooling?
No
It is simply the supply point and as such the inlet can be small IF the path thru and out is correct (back to the exit low pressure placement and shape)
Inlet drag is significant problem on full scale stuff- not on our models
Creating a full duct for best flow is simply beyond the ability or desire or understanding (NOT practical) for most hobbiests.
The best setup is to try to create a path which allows the low pressure to pull air thru the fins
You certainly can't blow it over and down around them .