Patent ID: 8807100

Claim:
A high expansion ratio engine equipped with a supercharger which is rotationally driven by means of exhaust gas and in which an expansion ratio is settable greater than a compression ratio, the engine comprising: an operation state determination unit that determines an operation state of the engine; a plurality of exhaust valves provided at a single cylinder; a variable exhaust valve timing mechanism that is capable of changing opening timing of at least one exhaust valve among the exhaust valves; and a controller that, when it is determined by the operation state determination unit that the engine is operated with a load equal to or more than a middle load and is in a steady supercharging operation state in which supercharging is performed by the supercharger, transmits a command to the variable exhaust valve timing mechanism and retards the opening timing of the at least one exhaust valve relative to the opening timing of another exhaust valve, compared with non-supercharging time of the supercharger.