Gm Global Technolgoy Operations, Inc.

Roberto Vernassa

Francesco Cianflone

Maura Dintino

Paolo Zamboni

A method and a control system are provided for diagnosing a diesel combustion catalyst that is located in an exhaust line within a diesel engine system. The method comprising providing an unburned fuel mass flow through the diesel oxidation catalyst, determining the oxidation heat release rate which is related to the exothermic oxidation reactions of the unburned fuel into the diesel oxidation catalyst, integrating the determined oxidation heat release rate on a time interval, integrating the unburned fuel mass flow on the same time interval, dividing the integrated value of oxidation heat release rate and the integrated value of unburned fuel mass flow for determining an efficiency index (DOI) of the diesel oxidation catalyst.

Method for diagnosing a diesel oxidation catalyst

In a fuel injection system of an internal combustion engine that includes, but is not limited to injectors (I-I), each of which is adapted to deliver a predetermined amount of pressurized fuel to a combustion chamber of a respective cylinder (C-C) of the engine, a high-pressure accumulator volume common to the injectors (I-I) and arranged to maintain the fuel at high-pressure, a pressure sensor for measuring fuel pressure in the accumulator volume, a metering unit for adjusting the fuel pressure in the accumulator volume as a function of the measured pressure, so as to maintain a predetermined target injection pressure set-point dependent on the engine operating point by returning excess fuel to a fuel tank; and an electronic control unit arranged for controlling fuel injection timing and quantity by operating injectors control valves, the operating pressure is controlled by triggering retarded injections (INJpost) of a predetermined quantity of fuel to the combustion chamber of the cylinders (C-C) of the engine during a respective exhaust stroke, when pressure above a predetermined threshold (THover) is detected in the accumulator volume, so as to discharge fuel from the accumulator volume without it taking part to the combustion process, thereby reducing pressure in the accumulator volume.

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Volpiano, Italy

Roberto Vernassa