War service demanded that gasoline engines be absolutely reliable in minor as well as major details of construction; lightness of construction was second in importance. The war scope of the gasoline engine was so wide that engineers were forced toward the solution of unexpected and unrealized problems and a vast amount of valuable data resulted. This information includes recent determination of the quantitative nature of the factors governing thermodynamic performance in respect to mean effective pressure, compression ratio and the effect of volumetric efficiency; mechanical performance in regard to mechanical efficiency and internal friction; and engine balancing. The problems of the past five years of intensive gasoline-engine experience, thus brought under critical survey for the first time, are discussed in the light of recent developments and a reexamination made of designers' existing practice to determine the trend of design regarding the obtaining of absolute mechanical efficiency; the application of modern views of gasoline engine thermodynamics; improvements in mechanical efficiency, engine balancing, carburetion and capacity to utilize low-grade fuels; the principles of light-engine design; and clean-cut design in general.
