Butterfly casing

The intake circuit is made up of the following components:

• air filter with relevant sleeves;
• acoustic resonator fitted in parallel to the inlet sleeve;
• inlet manifold, on which the fuel manifold is fitted;
• butterfly casing, where the butterfly position sensor, the PCV valve (Positive Crank Ventilation) for the oil vapour recirculation circuit and tne engine idle adjustment solenoid valve are fitted.

BUTTERFLY CASING

The butterfly casing has the task of metering the quantity of air supplied to the engine (and therefore the power developed) according to the driver's request via the accelerator control.

The butterfly casing is fixed to the inlet manifold by four bolts: the butterfly is opended by means of levers which create a small opening which, consistent with the pedal travel, produce small butterfly openings with the pedal gently pressed and viceversa large angle openings with the pedal strongly pressed. With the pedal completely released (engine decelerating or idling) the additional air required is supplied by the engine idle adjustment solenoid valve: under these circumstances the butterfly opening lever is in contact with screw which prevents the butterfly from being locked in the closed position.

To prevent the formation of ice in the butterfly and the port connected to the PCV valve, the butterfly casing is heated with a small amount of coolant coming from the engine thermostat circulating in a chamber inside the actual casing.

The PCV valve for the oil vapour recirculation system and the butterfly position sensor are also fitted on the butterfly casing.

The screw is adjusted during operation by fluxing in the factory and should never be tampered with.

1. Screw
2. Butterfly position sensor
3. Engine coolant inlet
4. Engine coolant outlet

1. PCV valve
2. Accelerator control lever
3. Accelerator cable adjustment bracket
4. Engine idle speed adjustment solenoid valve