The MAN L21/31 engine relies heavily on its pistons and piston rings, crucial components for maintaining engine compression and efficient combustion. Pistons, estimated at code H27222, withstand intense heat and pressure while transferring force to the crankshaft. The piston rings, likely coded around H31110 series, provide a critical seal between piston and cylinder walls to prevent gas leakage and control oil consumption. Regular inspection and timely replacement of these parts are vital for optimal engine performance and longevity.