Abstract: In an in-cylinder fuel injection engine capable of selectively switching a combustion strategy from a stratified charge combustion to a homogeneous charge combustion and vice versa, when a coolant temperature at engine start is lower than a specified temperature, the combustion strategy is established to be a homogeneous charge combustion mode and this homogeneous charge combustion mode is held until the coolant temperature reaches the specified temperature. While the coolant temperature is higher than the specified temperature and lower than a warm-up completion temperature, the combustion strategy is switched from homogeneous to stratified by lowering the engine load from a high load area to a low load area so as to improve emissions and fuel economy.

Abstract: Each cylinder of an internal combustion engine has two intake valves, two exhaust valves, a fuel injector and a spark plug. The fuel injector is vertically provided in a cylinder head of the engine such that a nozzle of the fuel injector is located in a central position of a combustion chamber. The spark plug is disposed between intake ports of the intake valves, so that an electrode of the spark plug is located near the nozzle of the fuel injector.

Abstract: A supercharging system has a turbocharger driven by exhaust-gas of the engine, a supercharger driven by an engine and communicated with the turbocharger and the engine in series. A clutch is provided in a device for driving the supercharger and a bypass having a control valve is provided around the supercharger. A control unit is provided to respond to engine operating conditions for operating the clutch and the control valve. The control unit operates to disengage the clutch at light load on the engine in a predetermined low engine speed range, to engage the clutch at heavy load in the low engine speed range, and to disengage the clutch in a predetermined high engine speed range. The control valve is gradually opened in accordance with variation of engine operation conditions when the engine operation is in a transient state.