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Exhaust emissions of a test gasoline engine were successfully reduced to 1/30 of the SULEV standards with the aim of minimizing the impact on the atmospheric environment. This reduction was achieved by reducing engine-out emissions from engine startup and by reconciling faster catalyst light-off with suppression of catalyst thermal degradation to avoid a decline in conversion efficiency. Specifically, a new intake gas flow control device and a low heat mass spark plug with high ignitability were developed for promoting post-oxidation of unburned HCs in the combustion chamber thus markedly reducing engine-out emissions, while ensuring acceptable drivability. The conflicting requirements for quicker catalyst light-off and avoidance of catalyst thermal degradation have been achieved at unprecedented levels by developing a new bypass-type exhaust manifold.

In this research, the effect of high-temperature residual gas, resulting from the application of a certain level of EGR, on combustion was investigated using a two-stroke engine and alcohol fuels (ethanol and methanol) and gasoline as the test fuels. Measurements were made of the light emission intensity of the OH radical on the intake and exhaust port sides of the combustion chamber and of the combustion chamber wall temperature (spark plug washer temperature) and the exhaust gas temperature. Data were measured and analyzed in a progression from normal combustion to autoignited combustion to preignition and to knocking operation.

The new all-wheel-drive control system has been developed to improve stability, handling performance and safety under various road/operating conditions. This system consists of center differential and hydraulic transfer clutch which is electronically controlled according to road/operating condition. The center differential of this control system is in the form of composite planetary gear system without a starter ring. The output torque of transmission is distributed by this center differential 35% to front wheels and 65% to the rear wheels. It improves handling performance on dry road when the transfer clutch is open. On the other hand, when the slippery road condition is detected or motion of vehicle is disturbed, the actual torque distribution is modified by electronically controlled transfer clutch to improve stability and safety.