A compression ignition engine (10) has a control system (24) for
processing data, one or more cylinders (16), a fueling system (18), and a
variable valve actuation mechanism (20). Control system (24) develops
both fueling data for fueling the engine and timing data representing
time during the engine cycle for intake valve closure to a cylinder that
will endow the cylinder with an effective compression ratio (ECR)
appropriate to current engine operation for causing auto-ignition to
occur near or at top dead center in the engine cycle. During a
compression upstroke, the cylinder is fueled according to the fueling
data and intake valve closure for the cylinder is performed according to
the timing data. This creates an air-fuel mixture that is increasingly
compressed to the point of auto-ignition near or at top dead center.