A method and system for using an internal combustion engine with dedicated EGR cylinders to provide an adjustable EGR rate to the main (non dedicated) cylinders. The dedicated EGR cylinder(s) are configured to receive fresh air via a fresh air intake or to receive a portion of the mixture of fresh air and EGR gas via the same mixed intake line that delivers intake to the main cylinders. If the dedicated EGR cylinder(s) receive only fresh air, the main cylinder(s) receive EGR at higher EGR rate. If the dedicated EGR cylinder(s) receive only the portion of fresh air and EGR gas, the main cylinder(s) receive EGR at a lower EGR rate. The EGR rate to the main cylinder(s) may be adjusted between these rates in response to operating conditions of the engine.
Robert W. Burrahm