Patent ID: 8682595

Claim:
A method to estimate a NO 2 concentration in an exhaust gas flowing through an exhaust pipe of an internal combustion engine, the exhaust pipe has a first section and a second section and is equipped with an aftertreatment device located between the first section and the second section, the method comprising: determining, at an electronic control unit (ECU), a parameter related to a NO 2 concentration of exhaust gas flowing in the first section, wherein the parameter related NO 2 concentration is a ratio of NO 2 to NOx in the exhaust gas; determining, at the ECU, an oxidization index expressive of a rate of NO contained in the exhaust gas which oxidizes into NO 2 inside the aftertreatment device; determining, at the ECU, a reduction index expressive of a rate of NO 2 contained in the exhaust gas which is reduced into NO inside the aftertreatment device; and calculating, at the ECU, a parameter related to the NO 2 concentration in the second section as a function of the parameter related to the NO 2 concentration in the first section, the oxidization index and the reduction index of the aftertreatment device.