A semirational method is developed for predicting steady-state power, smoke, exhaust temperature, and turbocharger speed of diesel engines (naturally aspirated (NA), turbocharged or turbo-intercooled) over a range of ambient conditions at constant fuel rate and engine speed. The equations are shown and prediction calculations can be performed on a slide rule. The basic assumptions, derivations, and a comparison of calculated predictions with test data are presented. A method of including the effect of fuel temperature on engine power is also given. The derivations and fundamental approach have been detailed in Appendixes B and C to assist other investigators. The addition of other factors not included by the authors may improve the accuracy or extend the useful range of the prediction equations.