OBJECTIVE: Wet flow, pressure excursions, port volume, runner length, plenum volume—all these figure into an engine's overall efficiency. But there's more… Sometimes theory is neat, but sometimes it ...

A.Pressure "excursions" (variations in intake manifold mixture flow pressures) are shown here in a trace of pressure vs. time (or crankshaft angle) in only one runner of a single-plane manifold. Since ...