ENGINE FOR USE IN A MACHINE

An engine (104) for use in a machine comprises an engine block (108). A cylinder head (106) is mounted to the engine block (108). A combustion chamber (126) is formed at least partially by the cylinder head (106). A piston (112) is slidably disposed in the engine block (108) and configured to reciprocate therein, wherein the piston (112) comprises a bottom surface (152), an outer surface (150) and a sidewall (147). The sidewall (147) faces radially outward to mate with a cylinder (110) of the engine (104). The sidewall (147) contacts the outer surface (150), the bottom surface (152) and the outer surface (150) forming a portion of the combustion chamber (126). The bottom surface (152) comprises a convex region (154) being intersected by a longitudinal piston axis (118) defined by the piston (112), a concave region (156), and a circumferential edge (166). The convex region (154) is radially inward of and in contact with the concave region (156), the concave region (156) is radially inward of and in contact with the circumferential edge (166), and the circumferential edge (166) is radially inward of and in contact with the outer surface (150).