Butterfly casing

BUTTERFLY CASING

The quantity of air drawn in is determined by the opening of the butterfly located at the start of the inlet manifold. The butterfly casing is fixed to the inlet manifold by four bolts; the butterfly is operated by the accelerator pedal by means of linkage which produces an opening system where in relation to the pedal travel, small butterfly opening angles are produced with the pedal slightly pressed and greater opening angles are produced with the pedal more depressed.

The air required to support the engine during idling and in load conditions with the butterfly valve closed is regulated and by-passed exclusively by the engine idle speed actuator.

A special screw (1), makes it possible to adjust the butterfly closure to prevent interference with the surrounding duct; this screw is not used for adjusting the idle as it is adjusted by fluxing in production and should not be tampered with under any circumstances.

The flow of engine coolant arriving from the thermostat flows through the inlet and outlet ducts (3) and (5) in the area of the butterfly valve has the aim of preventing condensation and the formation of ice which could be produced in particular low external temperature and/or high humidity conditions.

The gases which flow from the engine crankcase are drawn into the inlet manifold downstream of the butterfly through the PCV valve (4).

1. Butterfly valve adjustment and anti-tamper screw (not to be tampered with)
2. Butterfly opening control levers
3. Attachment for engine coolant supply pipe
4. Attachment for engine crankcase vapour recovery and recirculation pipe
5. Attachment for engine coolant return pipe
6. Engine idle speed actuator
7. Butterfly valve position sensor