A method for coordinating engine throttle position with camshaft phaser
motion during transient engine operation such that desired internal
residual dilution is maintained. A dilution model for residual mass
fraction and a table of desired dilution values are embedded in the
engine control algorithm. The dilution model is applied to calculate the
desired throttle and camshaft phaser positions for the next intake event.
In a first method, if the throttle is capable of changing the airflow
into the engine cylinders faster than the camshaft phasers can respond,
the throttle is modulated to maintain desired dilution levels while the
phasers are allowed to move as fast as they can. In a second method, if
the phaser response faster than the engine intake port airflow response
to a throttle position change, the throttle is allowed to move as fast as
it can while phaser motion is modulated to maintain desired dilution
levels.