Correlating reductant injection with NOx leve

摘要

A method of mapping the rate of reductant injection required to reduce NOx catalytically in a lean-burn internal combustion engine exhaust gas, to meet a required standard, comprises measuring the NOx in the exhaust gas as the vehicle is driven and correlating the measured value with at least one measurable parameter indicative of a condition of the engine. The at least one measurable parameter may be at least one of exhaust gas temperature, mass flow of exhaust gas, manifold vacuum, ignition timing, engine speed, throttle position, the lambda value of the exhaust gas, quantity of fuel injected into the engine, amount of exhaust gas recirculation, and boost pressure. The correlated value may be used to determine the amount of reductant required to reduce the measured value of NOx to a desired level or by a desired amount.