A direct injection controlled auto-ignition engine is operated at steady
state, within a homogeneous charge compression-ignition (HCCI) load range
and with fuel-air-diluent mixtures at predetermined conditions, for each
speed and load, of engine control inputs, including at least injection
timing (FI), spark timing (SI), throttle position, exhaust gas
recirculation (EGR) valve setting and exhaust recompression obtained by
negative valve overlap (NVO). During engine speed transients, the control
inputs are synchronized to changes in the current engine speed, and also
with any concurrent changes in the engine fueling rate. Inputs that are
inactive during all or part of a speed change have a zero change rate
while inactive. The method maintains robust auto-ignition combustion
during speed transients with constant or variable fueling rates and with
or without load changes.