Abstract: A direct-injection, spark-ignition engine of the present invention includes a turbo-charging device which promotes the temperature rise or activation of the exhaust-gas purification catalyst disposed downstream of a turbine during cold start. During engine cold start, the fuel injection by the fuel injector is divided into a leading fuel injection performed during the latter half of the compression stroke, prior to the ignition timing, and a trailing fuel injection performed during the expansion stroke, after the ignition timing. The amount of the intake-air and the amount of the fuel injection are so controlled that the air-fuel ratio in the combustion chamber during the combustion of the fuel by the leading fuel injection (a leading air-fuel ratio) is within the range of 2<&lgr;<3, and the air-fuel ratio in the combustion chamber during the combustion of the fuel by the trailing fuel injection (a total air-fuel ratio) is within the range of 1<&lgr;<2.

Abstract: A spark-ignition type 4-cycle direct injection engine is provided with a turbocharger for boosting intake air and an injector for directly injecting fuel to a combustion chamber within a cylinder, wherein in a &lgr;=1 region (II) and an enriched region (III) on the high-speed high-load side, fuel is injected during the intake stroke of the cylinder to attain a state of homogenous combustion. When the engine is in the high-speed side (specific region) of the enriched region (III), the air-fuel ratio A/F of the air-fuel mixture in the cylinder is controlled to become A/F≦13, the tumble flow T is strengthened by closing the TSCVs, and the opening degree of a wastegate valve of the turbocharger is controlled in order to increase the maximum boost pressure and compensate the drop in intake efficiency that is caused by closing the TSCVs.

Abstract: A spark-ignition type 4-cycle direct injection engine is provided with a turbocharger for boosting intake air and an injector for directly injecting fuel to a combustion chamber within a cylinder, wherein in a &lgr;=1 region (II) and an enriched region (III) on the high-speed high-load side, fuel is injected during the intake stroke of the cylinder to attain a state of homogenous combustion. When the engine is in the high-speed side (specific region) of the enriched region (III), the air-fuel ratio A/F of the air-fuel mixture in the cylinder is controlled to become A/F≦13, the tumble flow T is strengthened by closing the TSCVs, and the opening degree of a wastegate valve of the turbocharger is controlled in order to increase the maximum boost pressure and compensate the drop in intake efficiency that is caused by closing the TSCVs.

Abstract: A direct-injection, spark-ignition engine of the present invention includes a turbo-charging device which promotes the temperature rise or activation of the exhaust-gas purification catalyst disposed downstream of a turbine during cold start. During engine cold start, the fuel injection by the fuel injector is divided into a leading fuel injection performed during the latter half of the compression stroke, prior to the ignition timing, and a trailing fuel injection performed during the expansion stroke, after the ignition timing. The amount of the intake-air and the amount of the fuel injection are so controlled that the air-fuel ratio in the combustion chamber during the combustion of the fuel by the leading fuel injection (a leading air-fuel ratio) is within the range of 2&lgr;3, and the air-fuel ratio in the combustion chamber during the combustion of the fuel by the trailing fuel injection (a total air-fuel ratio) is within the range of 1<&lgr;<2.

Abstract: An engine has a torque peak in a middle engine speed range. An engine output control system reduces the engine output torque in the middle engine speed range so that the torque characteristic curve of the engine becomes flat when the vehicle is accelerated from a low engine speed range at a low gear speed.

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.