In endeavouring to present a paper on the relative problems of supercharging aircraft and motor-car power units, the author wishes to convey at the outset that no attempt is being made to give a scientific investigation of air compression, but rather to review the present stage of supercharger development, the difficulties which have to be met by the engine designer in applying such a device to a high-speed petrol engine, and with the hope of stimulating from this review a discussion on the possible advantages to be obtained thereby.

For the purpose of this paper, supercharging an internal combustion engine may be defined as :–The filling of the cylinder during each cycle by mechanical means in the form of a pump, with a greater amount of charge than would be possible with natural aspiration.