Influence of Atmospheric Pressure and Temperature upon the Performance of the Naturally Aspirated Four-Stroke C. I. Engine

The compression-ignition (C. I.) engine differs from other types of internal-combustion (I. C.) engine in that the fuel supply is entirely independent from the air supply and, further, that at all times a large excess of air is present. It is to be expected therefore that although the weight of air received will be influenced by atmospheric changes, the effect of these changes will be much less than in the case of an engine in which the fuel supply is dependent upon the air flow. Basically the effect is a change in air utilization, that is, air/fuel ratio. This is not universally realized as is shown by the fact that, quite frequently, a formula developed for correcting petrol-engine test results for atmospheric changes is applied to C. I. engine figures.The experiments described were designed to show the absurdity of this procedure and, if possible, to provide information from which a method of correcting C. I. engine results could be derived. The first objective is very definitely achieved; for the seco...