A study of all aspects of noise generated by small indirect injection diesel engines has been made, primarily aimed at the reduction of idling noise. This is a major problem in the application of diesel engines to taxis and light commercial vehicles when compared with the gasoline engine.
The inherent advantage shown by the indirect injection system, in terms of smoke, noise, and gaseous emissions, is resulting in an extension of its application into larger commercial vehicles.
Combustion is shown to be the major noise source under both idling and high-load, high-speed conditions, and means of reducing this by control of fuel injection are described, together with the reduction of the other noise sources contributing to the annoyance aspect of idling noise.