Valve trains employing a splined interface between phaser(s) and a concentric camshaft, actuator at rear of camshaft actuated by an actuation rod, adding a clearance hole to the lobe pin for clearance to the actuation rod, supplying oil to camshaft bearings via the concentric camshaft inner tube, and bolt on front camshaft bearing. The valve trains may further employ a third rocker lever that is usable for a selectable valve event (e.g. compression release brake) while also implementing variable valve timing and a concentric camshaft.

An arrangement of a camshaft phaser (1) which has a drive element (2) and at least two driven elements (3, 4), whereby the camshaft phaser (1) has a first control valve (7) arranged concentrically to the camshaft phaser (1), and a second control valve (8) arranged off-centered with respect to the rotational axis (5) of the camshaft phaser (1).

An internal combustion engine is configured to operate in a homogeneous-charge compression-ignition combustion mode and a spark-ignition combustion mode employing late intake valve closing. A method for operating the internal combustion engine includes determining an amount of residual gas re-inducted into a combustion chamber from a previous engine cycle and determining an amount of fresh air trapped in the combustion chamber for the present engine cycle based upon the amount of residual gas re-inducted into the combustion chamber from the previous engine cycle. Engine fueling to the cylinder for the present engine cycle is controlled based upon the amount of fresh air trapped in the combustion chamber for the present engine cycle.