On Fri, 19 Oct 2007 16:55:04 -0500, "Robert Swinney"
wrote:

Did you ever hear the one "Nature abhors a vacuum." Pull the air out of anything and gravity
pushing on the atmosphere causes it (the air) to rush in. Suction really has nothing to do with it,
except that was the method used to eliminate the air. Gasses can be eliminated in other ways, such
as the "getter" in the envelope of a vacuum tube at evacuation.

A correct answer would be "due to pressure differential". Manifold
pressure is seldom atmospheric. It's often lower (engine vacuum) in
an ordinary engine but it might be higher in a turbocharged engine.
"Suction" is created by a lower pressure region causing a pressure
differential, so "suction" is closer to right in this case.