Reduction of Ammonia Emission using Deceleration Cylinder Cutoff in a Gasoline Spark Ignition Engine

The newly proposed Euro 7 emission standards have added regulations limiting ammonia emissions for gasoline vehicles. This paper proposes a new emissions-control strategy to satisfy the regulated ammonia emission levels, using deceleration cylinder cut-off (DCCO) to reduce or eliminate conventional deceleration fuel cutoff (DFCO) and the associated lean-rich excursions in the three-way catalyst during oxygen saturation and desaturation. The improved air-fuel ratio management closer to stoichiometry lowers the ratio of CO to NO_x and thus the ammonia (NH₃) formation rate inside catalytic converter. Tests show more than 80% reduction of ammonia emission on the WLTC drive cycle without increasing other regulated emissions.