3363704 - INTRODUCTION - ENGINE AIR SUPPLY CIRCUIT

COMPOSITION

STRUCTURE

AIR SUPPLY SYSTEM1 - Air filter complete with resonator2 - Flow meter3 - Corrugated hose4 - Turbocharger5 - Air/air heat exchanger (intercooler)6 - Throttle body7 - Throttle casing control actuator8 - Intake chamber9 - Hose with resonator

DESCRIPTION OF COMPONENTS

THROTTLE BODY

Construction specifications

In order to limit the shuddering of the engine whilst it is switching off, a throttle casing has been introduced downstream of the air chamber which has the task of closing the flow of air to the cylinders.The throttle remains open in all other operating conditions.1 - Vacuum reservoir2 - Solenoid3 - Throttle casing control actuator4 - Throttle body5 - Injection control unit

Operation

When the engine is off, the throttle is open because no vacuum is present.When the engine is running, the throttle is open because the deactivated solenoid valve closes off the flow of the vacuum to the throttle casing pneumatic actuator.A vacuum builds up during engine operation.When the engine is turned off (the key is turned OFF), the injection control unit keeps the actuator supply relay supplied 4 or 5 seconds longer and simultaneously earths the solenoid valve. The valve then opens to send a vacuum to the pneumatic actuator which closes the throttle to cut off the air flow to the cylinders.