Development of Atmospheric Air-level Emission Vehicle Technology for Gasoline Engines 2009-01-1076
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. Moreover, the adoption of an HC trap catalyst developed in-house at Nissan also contributed to the attainment of cleaner emissions at levels equal to 1/30 of the SULEV standards. The levels achieved are comparable to the atmospheric concentrations of the measured species in urban areas.