Throttle casing

THROTTLE CASING

To reduce engine noise during shut-down, a throttle has been added to the intake port with the aim of closing off the air flow to the cylinders.

Throttle valve opening or closure is controlled by an engine control unit (5) that manages a control actuator (3) on throttle body (4) via solenoid (2).

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 Pierburg solenoid is not activated and prevents the vacuum reaching the pneumatic actuator.

A vacuum builds up in the tank during engine operation.

During engine shut-down (when the ignition key is turned OFF), the control unit keeps the actuator supply relay activated for a further 4 or 5 seconds and simultaneously earths the Pierburg valve. The Pierburg valve opens to send the vacuum that has built up in the vacuum tank to the pneumatic actuator, which closes the throttle to cut off the flow of air to the cylinders.

1. Vacuum tank;
2. Pierburg solenoid controlling throttle body actuator;
3. Pneumatic actuator on throttle body
4. Throttle case
5. Engine control unit
6. Vacuum pump