Abstract: An arrangement for a reciprocating internal combustion engines is provide that includes a reciprocating main piston and a smaller cell piston which works in cooperation with the main piston to vary the compression ratio of and igniting a fuel-air mixture in a homogenous compression ignition engine. An actuator controls movement of the smaller cell piston relative to movement of the main piston.

Abstract: A cylinder head of an engine is disclosed, the cylinder head including an upper deck, a lower deck, and a sidewall extending between the upper deck and the lower deck. The lower deck defines a block-engaging portion and a combustion chamber flame deck. The combustion chamber flame deck is spaced apart from the block-engaging portion. An engine is also disclosed that includes a cylinder block having a cylinder bore, and a piston slidably positioned within the cylinder bore. The engine also includes a cylinder head having a lower deck connected to the cylinder block, the lower deck defining a block-engaging portion and a combustion chamber flame deck. The combustion chamber flame deck is spaced apart from the block-engaging portion by a recess.