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The results are presented of an extensive series of tests on a turbocharged 4-stroke diesel engine in which the test results are compared with predictions using a generalized computer program. An examination is made of the influence of the cylinder heat transfer coefficient, the cylinder wall temperature, the exhaust pipe wall temperature, and the air valve flow areas on the engine and turbocharger performance predictions in order to establish the limits of accuracy required for these data. The effect of including the intake system in the calculation is also examined. Results are presented comparing the actual performance of the turbocharger with the predicted performance using steady flow data.

A mathematical model is developed to represent an oxidizing catalytic converter in the exhaust system of a spark ignition engine in which the flow is non steady. By using the basic mass transfer, heat transfer and chemical reaction rate equations on the path lines the heat generated at the catalyst surface and the friction factor are allowed for in the generalized non steady flow relations using the method of characteristics. The model is included in a multi-cylinder engine simulation program. Secondary air injection into the exhaust system is represented by a simple mixing process without chemical reaction. A series of tests were carried out on a four cylinder two litre engine with a carbon monoxide and hydrocarbon oxidizing converter and secondary air injection. Comparison of results between experiments and computer calculations shows excellent agreement when the converter is new, but that if the catalyst surface is poisoned or aged the hydrocarbon prediction deteriorates.