Abstract: An air-fuel ratio of an air-fuel mixture produced by fuel injected from a first injector into an intake port (or into a combustion chamber) is set in a range of 28 to 38. Therefore, when the temperature and pressure rise with a first combustion started by spark-ignition around a spark plug to the fuel injected from a second injector into the combustion chamber, the timing of starting a second compressive hypergolic ignition is optimized to provide a stable combustion state free of knocking and misfire.

Abstract: An air-fuel ratio of an air-fuel mixture produced by fuel injected from a first injector into an intake port (or into a combustion chamber) is set in a range of 28 to 38. Therefore, when the temperature and pressure rise with a first combustion started by spark-ignition around a spark plug to the fuel injected from a second injector into the combustion chamber, the timing of starting a second compressive hypergolic ignition is optimized to provide a stable combustion state free of knocking and misfire.

Abstract: A valve actuating apparatus for an internal combustion engine selectively operating in the normal Otto cycle or the Miller cycle is provided which enables the engine to achieve stable combustion and improved fuel economy during cruising or in a low-load engine operating region. A delayed-closing cam for Miller cycle operation and a normal cam having a cam profile for earlier valve-closing timing of the intake valve than a cam profile of the delayed-closing cam are provided on a camshaft. A cam profile-switching mechanism switches between the delayed-closing cam and the normal cam, for opening and closing the intake valve. An ECU controls the switching mechanism such that when a detected operating condition of the engine indicates starting or idling, the intake valve is operated by the normal cam, and when the detected operating condition indicates cruising, the intake valve is operated by the delayed-closing cam.

Abstract: A valve actuating apparatus for an internal combustion engine selectively operating in the normal Otto cycle or the Miller cycle is provided which enables the engine to achieve stable combustion and improved fuel economy during cruising or in a low-load engine operating region. A delayed-closing cam for Miller cycle operation and a normal cam having a cam profile for earlier valve-closing timing of the intake valve than a cam profile of the delayed-closing cam are provided on a camshaft. A cam profile-switching mechanism switches between the delayed-closing cam and the normal cam, for opening and closing the intake valve. An ECU controls the switching mechanism such that when a detected operating condition of the engine indicates starting or idling, the intake valve is operated by the normal cam, and when the detected operating condition indicates cruising, the intake valve is operated by the delayed-closing cam.