An engine system includes an engine housing forming a plurality of intake ports, and a plurality of fuel admission tubes each forming a fuel passage and at least one mixing air opening fluidly connected to the fuel passage between a first tube end and a terminal end surface of a second tube end. The mixing air opening may be formed in an end cap of the fuel admission tube. A plurality of mixing air openings in a fuel admission tube may have at least one of a circumferential distribution or an axial distribution that is biased in a direction of an incoming flow of intake air. Related apparatus and methodology is also disclosed.

An engine system includes an engine housing forming a plurality of intake ports, and a plurality of fuel admission tubes each forming a fuel passage and at least one mixing air opening fluidly connected to the fuel passage between a first tube end and a terminal end surface of a second tube end. The mixing air opening may be formed in an end cap of the fuel admission tube. A plurality of mixing air openings in a fuel admission tube may have at least one of a circumferential distribution or an axial distribution that is biased in a direction of an incoming flow of intake air. Related apparatus and methodology is also disclosed.

A plurality of injection holes include at least one flat injection hole while an outlet opening of the at least one flat injection hole has a long axis and a short axis, and the at least one flat injection hole includes at least one specific flat injection hole. The specific flat injection hole has an injection hole axis that connects between a center of an inlet opening and a center of the outlet opening, and the long axis of the outlet opening is perpendicular to a plane which includes the injection hole axis and is parallel with the valve axis. An inner wall of the outlet opening has two planar portions which are opposed to each other while the long axis is interposed between the planar portions.