Four-stroke cycle engine

摘要

A four-stroke cycle engine having intake ports openable to a combustion chamber in a cylinder head, said intake ports being connected to an intake manifold, said intake manifold being provided with a throttle valve for controlling the intake air flow rate, and having a sub-intake passage for connecting the upstream and downstream sides of said throttle valve; and a control valve disposed in said sub-intake passage for controlling the intake air flow rate. The downstream side ends of said sub-intake passage are open to said intake ports, and a check valve is disposed on the downstream side of said sub-intake passage from said control valve. <IMAGE>