Conventional diesel engines are fitted with a vacuum pump as standard, as they have no throttle valve and therefore cannot generate a vacuum. Vacuum pumps are also used in petrol engines if there is an insufficient vacuum in the intake manifold after the throttle valve.
Vacuum pump variants
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Vacuum pumps that move a piston or diaphragm back and forth have long proven their worth in the field. A more recent development is vane-type vacuum pumps with a rotary drive.
Vacuum pumps can be driven by means of cams, tappets, chains, belts or cam discs. Single-vane vacuum pumps are state-of-the-art: they are mostly mounted to the cylinder head and are driven by the camshaft. Electric vacuum pumps can be switched on independently of the vehicle engine as and when needed.