A method is provided for control of transition between combustion modes of
a direct-injection engine operable in a homogeneous charge compression
ignition (HCCI) mode at lower loads and a spark ignition flame
propagation (SI) mode at higher loads. The engine includes a variable
valve actuation system including two-step high and low lift valve
actuation and separate cam phasing for both intake and exhaust valves.
The method includes operating the engine at steady state, with
fuel-air-exhaust gas mixtures at predetermined conditions, for each speed
and load, and controlling the engine during mode changes between the HCCI
mode and the SI mode by switching the exhaust and intake valves between
low lift for HCCI operation and high lift for SI operation. High load may
be an SI throttled mode with an intermediate unthrottled mode (SI/NTLC}
in which transition between HCCI and SI/NTLC modes requires switching
only the exhaust valve lift and transition between SI/NTLC and SI
throttled modes requires switching only the intake valve lift, with
predetermined phase adjustments in the valve timing phasing.