Patent attributes
In a combustion control system, a control unit determines, based on an operating condition of an exhaust purifying device, whether a request for an exhaust temperature rise or a rich A/F ratio engine operating mode is present. The control unit executes, by way of fuel injection control in presence of the request of the exhaust temperature rise or the rich operating mode, a split retard combustion mode in which a main combustion needed to produce a main engine torque and at least one preliminary combustion occurring prior to the main combustion are both achieved, and the preliminary combustion occurs near top dead center on a compression stroke, and the main combustion initiates after completion of the preliminary combustion. The control unit simultaneously executes an exhaust-emission reduction control that reduces HC and CO emissions, while keeping the excess air factor at a desired value in the catalyst deactivated state.
