"The inlet is a strange thing to analyze -
It appears to be a "ram air " inlet - it isn't.
actually -the air behind the prop - at the base of the prop -is somewhat stagnant (?)
What I mean is that it is swirling and moving outward at that point on the prop--so no air is being rammed into the cowl.
The exit air (lowering of pressure in the cowl) is the controlling factor.
a very small inlet does the job as long as the exit air pressure drop is sufficient"

Dick I really don't understand that...

whereas in FS we were told:
Basic principles of air cooling

"The majority of aircraft piston engine cooling is done by air. The aircraft engine cowling is equipped with air inlets that allow the air to be directed into the engine compartment. On a standard design aircraft (with engine in front) the propeller and the relative wind drive air into the inlets. In cruise, the relative wind does most of the work of pushing air through the inlet. When the aircraft is flying the air entering the inlets is denser due to the ram action of flight. This ambient air creates a high pressure area inside the engine cowling than the static air around the aircraft."