Pressure waves in the inlet manifold of internal combustion engines have a significant effect on volumetric efficiency. This paper considers the possibility of generating further pressure waves as a method of increasing volumetric efficiency. A theoretical and experimental investigation, the former based on a novel linear model for supercharging, has revealed that actuators driven by the waves present in the waves, “passive” actuators, are able to significantly alter the volumetric efficiency; with ±15% changes demonstrated experimentally. Further improvement with energising or “active” actuators, however, requires more potent actuators than are in general use at present: to provide significant benefit, the power introduced by the actuator must be comparable to that of the natural excitation of the manifold by the induction stroke. A few possible classes of active actuators are discussed.