Method of controlling vehicle emissions

摘要

Disclosed is a method of controlling a vehicle engine. The method comprises the steps of determining at least two engine operational parameters selected from CO2 output, power output and NOx output; averaging the values of each of the two parameters during a driving time or distance window; providing a nominal reference curve relating the two engine parameters to each other; comparing the average value results with the reference curve to determine a measure of how far the parameter averages are from the reference curve and adjusting control of one or more engine systems dependent on the result. The method uses the deviation of at least two of an average NOx value, average CO2 value and average engine power from a curve showing an expected NOx, expected CO2 or expected engine power to provide an indication of the required control of one of the engine systems. These engine systems may relate to control of the urea dosage to a Selective Catalytic Reduction (SCR) system, Leant NOx Trap (LNT) regeneration frequency, Exhaust Gas Recirculation (EGR) rate, fuel injection timing or boost pressure in an engine having a turbocharger or supercharger. The method provides a means to control vehicle emissions to meet the required environmental emissions regulations across a wide range of real world driving conditions and is particularly applicable to internal combustion engine systems using exhaust gas recirculation.