A method for engine-out soot flow rate prediction of an exhaust gas treatment system is provided. A measured level of oxides of nitrogen in the exhaust gas treatment system is received. An engine fuel injection timing and air-fuel ratio of an engine producing the oxides of nitrogen are also received. An engine timing factor is determined based on the engine fuel injection timing. An engine air-fuel ratio factor is determined based on the engine air-fuel ratio. An engine-out soot flow rate prediction is generated based on the measured level of oxides of nitrogen, the engine timing factor, and the engine air-fuel ratio factor.