High expansion ratio internal combustion engine

A high expansion ratio internal combustion engine comprising:

• a variable compression ratio mechanism for changing a mechanical compression ratio of the internal combustion engine;
• a variable valve train in which some valve(s) of a plurality of intake valves arranged at a cylinder is phase-variable and the remaining valve(s) is phase-fixed;
• and
• a control unit for controlling the variable compression ratio mechanism such that the mechanical compression ratio of the internal combustion engine is increased and also controlling the variable valve train such that valve-close timing of the phase-variable intake valve is retarded after valve-close timing of the phase-fixed intake valve, when the internal combustion engine is under low-load operating state,
• wherein the variable valve train is configured such that a working angle of the phase-variable intake valve is larger than a working angle of the phase-fixed intake valve.