And for those wondering about intake manifold plenums.
The "ideal" plenum size is rougly 14 x engine capacity.
That would the Zetec's (2.0L) "ideal" plenum size about 28L.
28.3 Liters of air = 1 cubic ft of air.
Obviously the Zetec doesn't have a 1 cubic ft plenum on the intake manifold.
Its closer to 1/4 cubic feet.
