A vacuum delay valve is a valve with a small orifice, which delays a vacuum signal. These are commonly used in automobiles to alter the behavior of

vacuum switch Prior to effective engine control unit computers, engine vacuum was used for many functions in an automobile. Vacuum switches were employed to regulate this flow. For instance a dual port vacuum switch located in a port on the intake manifold mo ...

es,

vacuum motor A vacuum engine (also called flame-licker engine, flame-engine, flame-dancer) derives its force from air pressure against one side of the piston, which has a partial vacuum on the other side of it. At the beginning of an outstroke, a valve in the ...

s, and other vacuum devices. The engine in a common

automobile A car or automobile is a motor vehicle with Wheel, wheels. Most definitions of ''cars'' say that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, pe ...

produces almost of vacuum, and this pressure differential has been utilized for everything from automatic locks and

windshield wipers A windscreen wiper, windshield wiper, wiper blade (American English), or simply wiper, is a device used to remove rain, snow, ice, washer fluid, water, or debris from a vehicle's front window. Almost all motor vehicles, including cars, tru ...

to operating emissions control items.

Engine vacuum 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 c ...

is also the best direct source of information on the engine's load. Most delay valves have a one-way function, where there is either no restriction or no movement in one direction. Delay valves are usually color-coded to their function."1988 Jeep Cherokee Technical Service Manual.", "Spark Control System." Chrysler, 1987.

References

Valves Automotive technologies Pollution control technologies {{automotive-part-stub