Matching a Diesel Engine to Light Road Vehicles

Abstract

Reference to early use of Diesel engines in cars, etc., includes remarks on the application of heavier commercial transport engines. A list of ways in which the small Diesel has to compare more closely with the established petrol engine other than in fuel economy is followed by a description of experiments on a 1 1/2-litre four-cylinder design which fits a number of popular types of vehicle. Various difficulties met with are mentioned. In particular, valve gear and injection pumps required special attention. Specific outputs comparable and even higher than those of some contemporary petrol engines of the lower priced cars were obtained, but not without some noise and smoke. Graphs and tables show engine performance and data of injection processes and valve gear for maintenance of volumetric efficiency. It is shown that the Diesel and petrol engine size is similar, as are torque curves throughout the speed range. An automatic injection advance is necessary for reducing noise at low speeds and to keep performance up at high speed. Some road test figures are given; when the engine was installed in a typical 1 1/2-litre petrol car the effect was encouraging so far as performance and fuel consumption were concerned. There was room for improvement in engine noise. Exterior noise will require reduction by engine modification. Cold starting is an important problem and it is desirable to avoid the use of expensive aids. There is a reasonable expectation that the Diesel will be made attractive. Developments in injection pumps and possibly fuel will assist.