A method is disclosed for producing a piston (8) having a circumferential seal in the form of a circular cup seal (16). In a functional, installed state, the cup seal (16) has a profile consisting of a leg held in the piston (8) and aligned radially with respect to the piston longitudinal axis (19) in a radial region (17) and of a leg which is bent by approximately 90 into an axial region (18) and is aligned approximately parallel to the piston longitudinal axis (19). The cup seal (16) is mounted in a mold as a flat or arched preform (21, 21a) with a radial region (17a, 17b) which forms the approximately radial leg, aligned with the piston longitudinal axis (19). A circumferential region (18a, 18b) projecting radially beyond the mold cavity is shaped into the axial region (18) after removing the piston from the mold to obtain the functional contour of the installed state of the cup seal (16).

Disclosed herein is a method of treating a composite piston pin, including: preparing the piston pin of which at least surface layer includes a composite material including a reinforcing fiber and a resin; improving roughness by processing the surface layer of the piston pin; and forming a coating layer on the surface layer processed to reduce a friction coefficient of the piston pin.

A piston for a heavy duty diesel engine including a composite layer forming at least a portion of a combustion surface is provided. The composite layer has a thickness greater than 500 microns and includes a mixture of components typically used to form brake pads, such as a thermoset resin, an insulating component, strengthening fibers, and an impact toughening additive. According to one example, the thermoset resin is a phenolic resin, the insulating component is a ceramic, the strengthening fibers are graphite, and the impact toughening additive is an aramid pulp of fibrillated chopped synthetic fibers. The composite layer also has a thermal conductivity of 0.8 to 5 W/m.Math.K. The body portion of the piston can include an undercut scroll thread to improve mechanical locking of the composite layer. The piston can also include a ceramic insert between the body portion and the composite layer.