Spark-ignition engine ancillaries for better timing control - increase engine braking with reduced carbon monoxide emission

摘要

The equipment is for an engine with a carburettor utilising a butterfly valve (20). A pressure tapping (66) just downstream of the valve in its idling position applies a vacuum of small throttle openings and low engine speeds to one side (82) of a diaphragm (76) which rotates the contact-breaker so as to retard the ignition timing. At a certain threshold speed, solenoids (96 and 108) operate two slides valves (88 and 100), one of which applies a vacuum produced at large throttle openings at another tapping (64) in the carburettor to the other side of the diaphragm (76) to advance the ignition timing. If the throttle control is released at speeds above the threshold, vacuum is derived from a further inlet tapping (50) via a pre-loaded valve which now retards the ignition and slightly opens the butterfly valve; this provides engine braking torque.