METHOD FOR TREATING EXHAUST GASES OF A MOTOR VEHICLE

A method for treating exhaust gases from an internal combustion engine (2) in a motor vehicle (1) comprising an exhaust line (3) equipped with a selective catalytic reducer hereinafter SCR (5) and a reservoir (6) comprising a nitrogen oxide (NOx) reducing agent, this method comprises the following steps: - determination of the actual quantity (12) of NOx present in the exhaust gases, - determination of a quantity of NOx to be treated based on a predetermined limit quantity (13) of NOx to be released into the atmosphere, - determination of a flow rate (14) of reducing agent to be injected into the SCR (5) to eliminate the quantity of NOx to be treated, - injection of the flow rate (14) of reducing agent previously determined into the SCR (5), from the reservoir (6), - modification of operating parameters of the engine (2) in order to vary the quantity of NOx produced by the engine. The modification of the operating parameters of the engine (2) is carried out on the basis of a dimensionless number (24) calculated according to the following steps: - calculation of the volume (18) of reducing agent injected into the SCR between two consecutive refills of the reservoir (6), - measurement of the distance (20) traveled by the vehicle (1) between two consecutive refills of the reservoir (6), - calculation of a discretized flow rate (21) by dividing the volume (18) of reducing agent injected by the distance (20) traveled, - calculation of the dimensionless number (24) by dividing the discretized flow rate (21) by a predetermined limit consumption (23) of reducing agent, if the dimensionless number (24) is greater than 1, the modification of the engine parameters is carried out to reduce the quantity of NOx produced by the engine (2).