Patent ID: 8245502

Claim:
An emission control system comprising: a reductant injector injecting a pre-determined amount of a reductant into a vehicle exhaust passage; and sensors measuring an exhaust space velocity, a selective catalytic reduction (SCR) catalyst temperature, and a before-SCR nitrogen oxide (NO x ) concentration; wherein the predetermined amount of the reductant is a function of the exhaust space velocity, the before-SCR NO x concentration, and the SCR catalyst temperature according to equation (I) y=ax n , wherein y is the predetermined amount of the reductant; x is the product of the exhaust space velocity and the before-SCR NO x concentration; “a” and “n” are each independently a function of the SCR catalyst temperature; the SCR catalyst temperature being measured in degrees Celsius; the before-SCR NO x concentration being measured in parts-per-million (ppm); and the exhaust space velocity being measured in inverse hours (hr −1 ).