Combustion system:3.4.1.12.

The plunger's top face has a groove (54) which hold the cull (16) after each transfer molding cycle, thereby allowing the cull (16) retained on the plunger top face to be readily removed.

The spray is accommodated in the area (41) that is formed by the upper side of the piston, the lower side of the valve head and the upper inner wall of the can.

Said oil cooling channel having a bottom surface facing towards a top surface of said piston and a top surface facing away from said top surface of the piston.

The main portion of the upper surface of the piston is convex, while the main portion of the lower surface of the piston is less convex than the upper surface.

A pilot valve for relieving pressure above the piston has its inlet positioned within a cavity formed on the upper surface of the piston.

In one embodiment the upper surface of the piston extends to the piston rod (5) and is attached at it.

An upper surface of the piston, the piston cylinder and the cylinder head define a combustion chamber.

The additional air supplied therethrough is sufficient to substantially reduce heat transferred from the piston upper surface portion to the skirt of the piston.

Pressurized oil in a release chamber (12) formed at the upper side of the piston (5) moves the piston (5) downward for releasing.

A pilot valve for relieving pressure above the piston has its inlet positioned within a cavity formed on the upper surface of the piston.

At top dead center, a top face of the outer piston (14) maintains a substantially constant distance from an engine head assembly to minimize squish area variations.

In another embodiment, a recessed channel (9) may extend on the upper surface of the piston from the periphery of the piston towards its centre.

The piston (13) has a cavity (25) recessed at its center, and the height of the top surface of the piston (13) varies in the circumferential direction.

The upper surface of the piston is contoured to increase turbulence in the combustion chamber.