Various example approaches are described, one of which includes a method for adjusting relative delivery of liquid and gaseous fuel to a cylinder of the engine to effect rapid changes in cylinder air charge via changes in the displacement of fresh air by the gaseous fuel. In one particular approach, turbocharger lag is addressed by decreasing gaseous fuel injection while increasing liquid fuel injection to increase cylinder fresh air over and above any changes to fresh air via the throttle, wastegate, and/or turbocharger.