I did some research for you and came up with the following:
a reductant injection system for an internal combustion engine including a selective reduction system communicated with the internal combustion engine, a vehicle sensor communicated with the internal combustion engine, a controller, wherein the controller is communicated with the selective reduction system and the vehicle sensor and a reductant storage device communicated with the selective reduction system. In addition, a method for increasing NOx conversion efficiency in an internal combustion engine having a reductant injection system is provided, wherein the method includes obtaining a vehicle data signal responsive to the engine performance of the internal combustion engine, processing the vehicle data signal so as to determine a combustion characteristic of a combustion cylinder, determining an optimum reductant injection timing and introducing a predetermined amount of reductant into the combustion cylinder responsive to the optimum reductant injection timing. Furthermore, a medium encoded with a machine-readable computer program code for increasing NOx conversion efficiency in an internal combustion engine having a reductant injection system is provided, wherein the medium includes instructions for causing controller to implement the aforementioned method.
I hope this will give you an idea. Well not quite but a GENERAL COMPLICATED IDEA. Don't say it I know; I made it worse!!!