16. The apparatus of claim 13 , wherein said aftertreatment system comprises a selective catalytic reduction device; and wherein said modulating aftertreatment comprises dosing urea injection based upon said NOx creation estimation.
13. Apparatus for estimating NOx creation in a combustion process of a four-stroke internal combustion engine including a variable volume combustion chamber defined by a piston reciprocating within a cylinder between top-dead center and bottom-dead center points, intake and exhaust passages, and intake and exhaust valves controlled during repetitive, sequential exhaust, intake, compression and expansion strokes of said piston, said apparatus comprising: a pressure sensor generating pressure sensor readings describing conditions within said combustion chamber; a NOx estimation module including logic operations comprising: monitoring said pressure sensor readings; modeling a mass fraction burn value for combustion within the combustion chamber based upon said pressure sensor readings, wherein said mass fraction burn value indexes a crank angle at which a selected percentage of injected fuel is burned in a combustion cycle; estimating a state of combustion within the combustion chamber based upon the mass fraction burn value, the state of combustion comprising a combustion phasing and a combustion strength; and and estimating NOx creation with an artificial neural network based upon said state of combustion; and an aftertreatment system receiving an exhaust gas flow from said engine and modulating aftertreatment based upon said NOx creation estimate.