A method to control operation of an engine during a transition from a
first to a second combustion mode is provided. The engine includes a
controllable throttle valve, a variable valve actuation system for
controlling openings and closings of intake and exhaust valves, and, an
intake and an exhaust. Mass airflow, intake manifold pressure, and
cylinder volume to operate the engine in the second combustion mode and
meet an operator torque request are determined. Current states for mass
airflow, intake manifold pressure, and cylinder volume are determined. An
opening position of the controllable throttle valve and the openings and
the closings of the intake and exhaust valves are controlled during the
transition to the second combustion mode based upon differences between
the current states for mass airflow, intake manifold pressure, and
cylinder volume, and, the mass airflow, the intake manifold pressure, and
the cylinder volume.