A reciprocating piston-type internal combustion engine includes an engine cylinder, an intake port, an intake runner providing a passage through which intake gas enters the cylinder through the intake port, an intake valve for opening and closing the intake port, and a first flap located in the intake runner upstream from the intake valve, arranged in series with the intake valve, and having first and second positional states that vary during each engine cycle. The first state opens the intake runner passage to permit intake gas to enter the cylinder through the intake port. The second state at least partially closes the intake runner passage to control the flow of gas exiting or entering the cylinder through the intake port.