Limiting NOx emissions of a compression ignition internal combustion engine

A method for controlling an internal combustion engine (10) limits emission of undesirable compounds of nitrogen and oxygen and provides increased transient power, the method comprising: operating the engine at a first power output by providing a first air/fuel mixture to a combustion chamber of the engine; receiving a request for an increased power output from the engine, that is greater than the first power output; providing a second air/fuel mixture to the combustion chamber of the engine, the second air/fuel mixture comprising a greater amount of fuel than the first air/fuel mixture; and treating a flow of exhaust gas with a non-urea aftertreatment to reduce a level of pollutant in the exhaust gas during a fuel enriched operation of the engine to invoke the real-time removal reduction of the pollutant while increasing engine power.