The system cost $ 59.50, but offered stick-shift economy, performance, and driver control without a clutch pedal by using engine oil pressure and intake manifold vacuum to engage and disengage the clutch when shifting gears.
32.
Manifold vacuum should not be confused with venturi vacuum, which is an effect exploited in carburetors to establish a pressure difference roughly proportional to mass airflow and to maintain a somewhat constant air / fuel ratio.
33.
Prior to the introduction of Federal Motor Vehicle Safety Standards in the USA by the National Traffic and Motor Vehicle Safety Act of 1966, it was common to use manifold vacuum to drive windscreen wipers with a pneumatic motor.
34.
This manifold vacuum can be substantial, and can be used as a source of automobile ancillary power to drive auxiliary systems : power assisted brakes, emission control devices, cruise control, ignition advance, windshield wipers, power windows, ventilation system valves, etc.
35.
Worn valve guides and / or defective oil seals can often be diagnosed by a puff of blue smoke from the exhaust pipe on releasing the accelerator pedal after allowing the engine to overrun, when there is high manifold vacuum.
36.
The Corsa came standard with an instrument panel featuring a speedometer with resettable trip odometer, a 6, 000 rpm tachometer, cylinder head temperature gauge, analog clock with a sweeping second hand, a manifold vacuum / pressure gauge and fuel gauge.
37.
The tops of the rods are connected to a vacuum piston or a mechanical linkage which lifts the rods out of the main jets when the throttle is opened ( mechanical linkage ) or when manifold vacuum drops ( vacuum piston ).
38.
A relatively small diameter booster unit is required; for a very conservative 50 % manifold vacuum, an assisting force of about 1500 N ( 150 kgf ) is produced by a 20 cm radius diaphragm with an area of 0.03 square meters.
39.
An exception to this generalization is newer diesel engines meeting stricter emissions standards, where a throttle is used to generate intake manifold vacuum, thereby allowing the introduction of exhaust gas ( see EGR ) to lower combustion temperatures and thereby minimize NOx production.
40.
The intake air mass is measured with a " hot-wire " mass airflow sensor : drawn in by intake manifold vacuum, air moves past an electrically-heated wire filament, and the degree to which the filament is cooled indicates the mass of the airstream.
