Apparatuses, systems and method for utilizing multi-zoned combustion chambers (and/or multiple combustion chambers) for achieving compression ignition (and/or spark-assisted or fuel-assisted compression ignition) in an internal combustion engine are provided. In addition, improved apparatuses, systems and methods for achieving and/or controlling compression ignition (and/or spark-assisted or fuel-assisted compression ignition) in a Siamese cylinder internal combustion engine are provided.

An engine block comprising: a combustion chamber, an inlet for introducing a fuel/air mixture into the combustion chamber and an outlet for expelling combusted fuel/air mixture from the combustion chamber; and a piston that reciprocates within the combustion chamber to compress the fuel/air mixture therein, the piston having a closer supported thereon, wherein reciprocating movement of the piston seals the combustion chamber with the closer.

An engine block comprising: a combustion chamber, an inlet for introducing a fuel/air mixture into the combustion chamber and an outlet for expelling combusted fuel/air mixture from the combustion chamber; and a piston that reciprocates within the combustion chamber to compress the fuel/air mixture therein, the piston having a closer supported thereon, wherein reciprocating movement of the piston seals the combustion chamber with the closer.