Factors Affecting the Utilization of Anti-knock Quality in Automobile Engines

Abstract

In this paper the author has compiled an interim report based on a close study of the anti-knock requirements and fuel utilization of a number of modern automobile engines. It is found that the maximum octane requirements of most of the engines tested are related to then-indicated mean effective pressures. Considerable differences, however, exist in the performance of the engines when run on a fuel of the same quality in each case. A comparison is made between several engines operated on gasolenes of United Kingdom “Pool” and United States “Premium” grade quality, and it is shown that these engines vary considerably in the benefit they derive from the better classes of fuel. It is concluded that, in order to obtain the maximum benefit of a given anti-knock quality of fuel, an engine should be over-compressed and operated with retarded ignition at full throttle. The characteristics of side-valve engines are given special consideration, and the desirability of restricting full throttle spark advance at high speed is mentioned. Carburation requirements for good fuel utilization are also dealt with, and the effects of combustion chamber deposits are discussed.