Abstract: The present invention is a dual-stage fuel injection strategy for compression ignition engines in which 15-40% of the fuel is injected into the combustion chamber no later than about −20 to −30 CA ATDC and as early as IVC. The rest of the fuel is then injected in one or more fuel pulses, none of which start before about −20 to −30 CA ATDC. The fuel injected early in the compression stroke forms a lean mixture that burns with low soot and low NOx emissions. The combustion of that fuel serves to increase in-cylinder temperature such that the ignition delay of subsequent fuel injection pulses is short. This mode is utilized when it is predicted that a NOx spike is imminent. Various other alternative methods for reducing NOx spikes are also disclosed such as specialized EGR systems that can provide EGR with low manifold vacuum.

Abstract: The present invention is a dual-stage fuel injection strategy for compression ignition engines in which 15-40% of the fuel is injected into the combustion chamber no later than about −20 to −30 CA ATDC and as early as IVC. The remaining fuel is then injected in one or more fuel pulses, none of which start before about −20 to −30 CA ATDC. The fuel injected early in the compression stroke forms a lean mixture that burns with low soot and low NOx emissions. The combustion of that fuel serves to increase in-cylinder temperature such that the ignition delay of subsequent fuel injection pulses is short. This mode is utilized when it is predicted that a NOx spike is imminent. Various other alternative methods for reducing NOx spikes are also disclosed such as specialized EGR systems that can provide EGR with low manifold vacuum.

Abstract: A method and system for controlling combustion mode in an internal combustion engine is disclosed. A method for controlling a multi-cylinder internal combustion engine includes operating a portion of the cylinders according to a first combustion mode and operating a second portion of the cylinders according to a second, different combustion mode. The net torque produced by the cylinders equals driver demanded torque. By this invention, a first combustion mode, which has a desirable combustion characteristic such as high fuel economy or low emissions, but which cannot provide driver demanded torque if used in all cylinders, can be used in combination with a second combustion mode, thereby meeting driver demand for torque and gleaning the benefits of the first combustion mode.

Abstract: A method and system for controlling combustion mode in an internal combustion engine is disclosed. A method for controlling a multi-cylinder internal combustion engine includes operating a portion of the cylinders according to a first combustion mode and operating a second portion of the cylinders according to a second, different combustion mode. The net torque produced by the cylinders equals driver demanded torque. By this invention, a first combustion mode, which has a desirable combustion characteristic such as high fuel economy or low emissions, but which cannot provide driver demanded torque if used in all cylinders, can be used in combination with a second combustion mode, thereby meeting driver demand for torque and gleaning the benefits of the first combustion mode.