Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere.
Manifold vacuum is an effect of a piston's movement on the induction stroke and the choked flow through a throttle in the intake manifold of an engine. It is a measure of the amount of restriction of airflow through the engine, and hence of the unused power capacity in the engine. In some engines, the manifold vacuum is also used as an auxiliary power source to drive engine accessories and for the crankcase ventilation system.
Manifold vacuum should not be confused with venturi vacuum, which is an effect that is exploited in carburetors to achieve a fixed mix ratio between fuel and air.
Read more about Manifold Vacuum: Overview, Modern Developments, Manifold Vacuum Vs. Venturi Vacuum, Manifold Vacuum in Cars
Famous quotes containing the words manifold and/or vacuum:
“They had met, and included in their meeting the thrust of the manifold grass stems, the cry of the peewit, the wheel of the stars.”
—D.H. (David Herbert)
“No, it wasn’t an accident, I didn’t say that. It was carefully planned, down to the tiniest mechanical and emotional detail. But it was a mistake. It was a beaut. In the end, somehow granted the time for examination, we shall find that our so-called civilization was gloriously destroyed by a handful of vacuum tubes and transistors. Probably faulty.”
—John Paxton (1911–1985)