Valve duration control system for four-cycle engine

摘要

A control system for a four-cycle internal combustion engine controls a cam drive mechanism for an intake valve such that a cam of the cam drive mechanism maintains a valve open duration of the intake valve at a short valve open duration in response to a shift from engine operation at low speed with low load to engine operation at low speed with high load, and the cam increases the valve open duration of the intake valve in response to a shift from engine operation at low speed with low load to engine operation at low speed with middle load that is higher than the low load but lower than the high load.