Abstract: Present day diesel engines having aluminum piston assemblies are limited to combustion chamber pressures of approximately 12,410 kPa (1,800 psi) whereas the desire is to increase such pressures up to the 15,170 kPa (2,200 psi) range. To reach such levels the instant engine has a piston assembly including a steel piston member having an upper cylindrical portion of a diameter D and defining a top surface, a depending tubular wall having a top ring groove a minimal elevational distance TRH below the top surface, and an annular cooling recess located beneath the top surface and juxtaposed to the top ring groove for removing heat away therefrom in use. The piston member is preferably forged and subsequently machined to precisely controllable dimensions, and has a ratio of TRH to D of less than 0.06. Moreover, the piston assembly is preferably of the articulated type and includes a forged aluminum piston skirt connected to the piston member through a common wrist pin.

Abstract: An improved piston assembly including a generally cylindrical piston body having a crown, a depending relatively short ring land and a central cavity comprising inner and outer chambers. Seal receiving grooves are disposed in the ring land and are adapted to receive sealing rings, one of the grooves being specifically adapted to receive an oil ring. A generally cylindrical skirt body is provided and has an end in proximity to the piston body adjacent the ring land and is aligned with the piston body. An annular groove in the end of the skirt body opens into the outer chamber of the central cavity for receiving cooling oil draining from the cavity and for splashing the cooling oil against the interior of the piston body to cool the same. Bores from the oil ring receiving groove convey oil from such groove to the annular groove.