3026086 - Introduction - ENGINE AIR SUPPLY CIRCUIT

COMPOSITION

STRUCTURE

AIR SUPPLY SYSTEM1 - Air cleaner with resonator 2 - Flow meter 3 - Corrugated hose 4 - Turbocharger 5 - Air-Air heat exchanger (intercooler) 6 - Throttle body 7 - Throttle body actuator 8 - Air chamber 9 - Hose with resonator

COMPONENT DESCRIPTIONS

THROTTLE BODY

Construction features

To reduce engine judder when it is being switched off, a throttle body has been fitted upstream of the air chamber to cut off air flow to the cylinders.Under all other operating conditions, the throttle body remains open.1 - Vacuum reservoir 2 - Solenoid 3 - Throttle body actuator 4 - Throttle body 5 - Fuel injection control unit

Operation

With the engine switched off, the throttle is open because there is no vacuum.With the engine running, the throttle is open because, as the Pierburg solenoid valve is not supplied, it prevents the vacuum from reaching the pneumatic actuator.The vacuum accumulates in the reservoir whilst the engine is running.Whilst the engine is being switched off (when the key is turned to the OFF position), the control unit keeps the actuator relay feed supplied for 4 or 5 seconds and, at the same time, places the Pierburg solenoid valve to earth which, on opening, sends the vacuum, which has accumulated in the vacuum reservoir, to the pneumatic actuator which closes the butterfly interrupting the flow of air to the cylinders.