Abstract: An oil cooled diesel engine piston is designed to restrict heat loss from the combustion chamber through provision of a combustion chamber insert defining a central non-oil-cooled chamber and a surrounding annular insulating air gap. The air gap controls heat flow primarily between the combustion gas exposed wall of the insert and an adjacent coolant exposed wall of the main piston volume.The insert is press fitted into a recess in the main piston body and is positively locked therein by a retaining ring. A seal ring closes expansion clearance provided at the upper edge of the insert against significant gas flow into the insulating air gap. Insulating efficiency of the air gap is maximized by forming the gap with a thickness throughout a major portion of its extent of between about 0.040 and 0.060 inches.Numerous additional features are also disclosed.

Abstract: An oil cooled diesel engine piston is designed to restrict heat loss from the combustion chamber through provision of a combustion chamber insert defining a central non-oil-cooled chamber and a surrounding annular insulating air gap. The air gap controls heat flow primarily between the combustion gas exposed wall of the insert and an adjacent coolant exposed wall of the main piston volume.The insert is press fitted into a recess in the main piston body and is positively locked therein by a retaining ring. A seal ring closes expansion clearance provided at the upper edge of the insert against significant gas flow into the insulating air gap. Insulating efficiency of the air gap is maximized by forming the gap with a thickness throughout a major portion of its extent of between about 0.040 and 0.060 inches.Numerous additional features are also disclosed.