Ram air

The Mooney 201 has a ram air port, a half a foot under the prop
spinner. The POH tells us it can be opened at altitude for a very
modest increase in MP and we find maybe a half inch increase in
pressure. The idea of the thing is, if the port is looking right at
the air being thrust toward it by the prop (it can't be more than 6
inches or so behind it) as well as the air impact from the airplane's
motion the air being 'rammed' into it should effectively lower the
altitude the engine thinks it's at. Well, a half inch of Hg is about
500 feet or so. The question is, though, wouldn't you think there
would be a way to capture a great deal more of the ram air effect and
really boost the engine performance? Who wouldn't like to fly at 24
square at 12000 feet without a turbo charger?

What makes me wonder about it is, even at 60 mph holding your hand out
of the window of a car subjects it to a significant backward pressure,
so the energy must be there.