Abstract: A turbocharged engine is provided with a waste gate valve which limits the supercharging pressure in the intake passage downstream of the compressor of the turbocharger not to exceed a predetermined value. The intake passage has first and second pressure propagating paths downstream of the compressor. The pressure wave generated by the intake stroke of the combustion chamber is propagated substantially along the first pressure propagating path when the engine operates at a speed in a low engine speed range under heavy load and substantially along the second pressure propagating path when the engine operates at a speed in a high engine speed range.

Abstract: An engine intake system including a supercharger of a type wherein the intake air drawn from the intake air inlet port is compressed by the pressure of the exhaust gas before it is discharged through the intake air outlet port. An exhaust gas recirculation passage is provided between the exhaust passage upstream of the supercharger and the intake passage downstream of the supercharger. The recirculation passage can be used for decreasing the pressure difference between the exhaust gas and the intake air to thereby minimize the engine pumping loss. Further, the recirculation passage can be used for recirculating the exhaust gas to the intake passage to thereby decrease nitrogen oxides in the exhaust gas.