Patent ID: 8635030

Claim:
A method for determination of a NOx concentration value upstream of a Selective Catalytic Reduction (SCR) catalyst in a Diesel engine, the Diesel engine comprising an exhaust line, a Diesel Particulate Filter (DPF) and a NOx concentration sensor downstream of the SCR catalyst, the method comprising: estimating, at a control apparatus, the NOx concentration value upstream of the SCR catalyst as a function of at least two engine parameters to provide an estimated value; measuring the NOx concentration value downstream of the SCR catalyst using the NOx concentration sensor to provide a measured value; calculating a difference Z(x, y) between the estimated value and the measured value; and correcting, with the control apparatus, said estimated value with a NOx concentration correction value if said difference is higher than a predetermined threshold, wherein said NOx concentration correction value is calculated using a correction map that correlates said at least two engine parameters and said difference Z(x, y) with said NOx concentration correction value.