System and method for operating an engine

摘要

A method for operating an engine is disclosed. In one example, internal EGR is increased during conditions where cooled EGR is at a higher concentration during a decreasing engine load so that homogeneous compression ignition may be initiated at lower engine loads.

主权项

1. A method for operating an engine including cooled EGR, comprising:
supplying cooled EGR to engine cylinders; and increasing a concentration of internal EGR supplied to the engine cylinders in response to a concentration of cooled EGR supplied to the engine cylinders during a reduction in engine load, where the concentration of internal EGR is increased as the concentration of cooled EGR increases, and further comprising decreasing the concentration of cooled EGR supplied to the engine cylinders via closing an EGR valve and increasing intake and exhaust valve opening time overlap during the reduction in engine load until a rate of decrease in engine load exceeds a threshold rate of decrease in engine load.