Abstract: In an internal combustion engine with a supercharger, a timing or timings for varying characteristics of kinetic supercharging effects of intake air are synchronized with a timing or timings for varying supercharging pressures by the supercharger. Reduction in engine torque at the time when the supercharging pressure is shifted, can be compensated for by enhancement in the engine torque generated at the time when the characteristics of the kinetic effect are varied.

Abstract: A supercharged engine has a geometric compression ratio of more than 8.5, and engine specifications are set to establish a relation, Y.gtoreq.-1.75X+10, in which an intake port closing timing Y is expressed by a crank angle after the piston reaches BDC and an overlapping angle X is expressed by a crank angle for an overlapping time period during which the intake valve and exhaust valve are both open.

Abstract: An exhaust device for use in an internal combustion engine includes a plurality of independent passages each connected to an exhaust port of a respective cylinder of the engine. At least one communicating passage is provided to connect the independent passages to each other at points upstream of a junction where the independent passages are joined together. The communicating passage permits the exhaust gases from one cylinder to flow into the independent passages for the other cylinders, thus lowering the gas temperature and improving fuel comsumption.

Abstract: In a turbocharged engine, a bypass passage bypassing the impeller of the turbocharger is provided in the intake system to be opened and closed by a bypass valve. A flow control valve is provided in the intake system on the intake side or discharge side of the impeller. During heavy load operation of the engine, the bypass valve is closed and the flow control valve is opened so that all intake air flows through the impeller of the turbocharger. On the other hand, during light load operation of the engine, the bypass valve is opened and the flow control valve is partly closed so that the ratio of the pressure in the intake system downstream of the impeller to the pressure in the intake system upstream of the impeller is set near the surging line but below the same.

Abstract: An intake system for an internal combustion engine has an intake passage comprising a common passage portion opening to the atmosphere, a surge tank connected to the downstream end of the common passage portion and a plurality of discrete passage portions branching from the surge tank and respectively connected to the cylinders. At least one interconnecting passage is provided to communicate each of the discrete passage portions with at least one of the other discrete passage portions at a portion downstream of the surge tank, and an on-off valve is disposed at each junction of the interconnecting passage with the discrete passage portions to open and close each junction. The on-off valve is opened at least when the engine speed exceeds a predetermined speed during heavy load operation of the engine.

Abstract: An intake system for a multicylinder internal combustion engine comprises an intake passage including a common passage portion opening to the atmosphere, first and second volume chambers communicated with each other by a communicating passage, and a plurality of discrete passage portions branching from the first volume chamber and respectively connected to the cylinders. The second volume chamber is arranged to communicate the discrete passage portions with each other at a portion downstream of the first volume chamber and the common passage portion is communicated to one of the first and second volume chambers. An on-off valve is disposed at each junction of the second volume chamber with the discrete passage portions to move between an open position and a closed position in which the effective cross-sectional area of the junction is narrowed to an extent sufficient to prevent reflection of the pressure wave generated in the discrete passage portion at the second volume chamber.

Abstract: A multiple cylinder engine having an intake passage for each cylinder. A shut-off valve or valves are provided in the intake passage or passages leading to selected one or ones of cylinders downstream of the throttle valve. The shut-off valve is closed in idling operation so that the combustible mixture is totally supplied to the remainder of the cylinders to increase the mixture charge therein. The intake passage or passages leading to the selected cylinder or cylinders are supplied with air when the shut-off valves are closed so that the peak pressure in such cylinders is increased. The air supply is cut-off in deceleration in order for preventing the engine-brake effect from being weakened.