Abstract: A cylinder having at least one intake port and at least one exhaust port, wherein the at least one intake port includes an upper surface and a lower surface, the upper surface of the intake port having an entrance portion and an outlet portion, the upper surface arced from the entrance portion to the outlet portion.

Abstract: A cylinder having at least one intake port and at least one exhaust port, wherein the at least one intake port includes an upper surface and a lower surface, the upper surface of the intake port having an entrance portion and an outlet portion, the upper surface arced from the entrance portion to the outlet portion.

Abstract: An engine is provided which includes various precise configuration parameters, including dimensions, shape and/or relative positioning of the combustion chamber features, resulting in a combustion process minimizing NOx emissions and particulates. The combustion chamber includes one or more of the following: a spray angle relative to an inner bowl floor angle; a vertical distance from the tip of the piston bowl to the injection orifices; a number of injection orifices; a swirl ratio; a vertical distance from the injection orifices to an inner face of the cylinder head; a radius of curvature of an outer bowl section; chamfer with dimensional parameters; and a transition radius.

Abstract: The swirl control system is provided for varying the swirl of intake air in an internal combustion engine comprising a primary intake air passage for delivering a primary flow of intake air having an initial angular momentum corresponding to a low swirl energy level and a secondary intake air passage connected to the primary passage for directing a secondary air flow at a predetermined flow rate into the primary air flow to form a combined air flow having a combined angular momentum greater than the initial angular momentum of the primary air flow. The secondary air flow enters the primary passage substantially tangential, to the primary air flow so as to substantially avoid destructive interference with the primary air flow thereby minimizing pressure losses in the primary passage. A secondary air flow control valve for controlling the flow of secondary air into the primary passage is operable to vary the combined angular momentum so as to vary the swirl of intake air in the combustion chamber.