Engine control systems and methods for nitrogen oxide reduction
A fuel control module controls fuel injection of an engine based on a predetermined lean air/fuel ratio. The predetermined lean air/fuel ratio is fuel lean relative to a stoichiometric air/fuel ratio for the fuel. A cylinder control module selectively deactivates opening of intake and exhaust valves of M cylinders of the engine to increase removal of nitrogen oxide (NOx) from exhaust. M is an integer greater than 0 and less than a total number of cylinders of the engine. The fuel control module further: disables fueling of the M cylinders while opening of the intake and exhaust valves of the M cylinders is deactivated; and, while fueling of the M cylinders is disabled and opening of the intake and exhaust valves of the M cylinders is deactivated, controls fuel injection of other cylinders based on a predetermined rich air/fuel ratio that is fuel rich relative to the stoichiometric air/fuel ratio.