Probably no one here has heard of pressure cowls -but anyway they were common on speed control line-back when the earth was still flat --
The idea is a small inlet that feeds ONLY into the finned (usually cut way down) section of the cylinder -which fits very closely to the sides of cyl
the outlet is large and situated such that air is extracted .
One can not ram air into the opening - simply can't do it.
the prop in this area is only a spinning log - actually worse than it would be without a prop.