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The improvement of exhaust emission during engine warm-ups is vital in engine emission control as engine emission limits are constantly lowered. An effective solution to this problem is to install a rapid-warming catalyst. On the other hand, precaution also has to be taken to avoid overheating of the catalyst. These require detailed information on heat transfer and accurate gas temperature variations at different locations in the exhaust system. In this study, experiment was conducted to investigate how mean gas and pipe wall temperatures vary during warm-ups throughout the exhaust systems, as well as the time constants of the transient processes. In addition, a program was developed for the simulation of exhaust gas and pipe wall temperatures during warm-ups. The temperatures were time-averaged in every engine cycle but variable from cycle to cycle.

An extensive amount of research has been carried out by various authors on the entrainment of fuel droplets in a steady air flow, in order to understand the transportation of droplet fuel in the spark-ignition engine intake manifold system. However, the utility of this type of steady state model is very limited when applied to the real engine where the air flow is highly pulsative. The present work develops a theoretical model of the flow of fuel droplets entrained in a non-steady air flow which requires the solution of a set of unsteady one-dimensional two phase flow equations by a numerical technique. This model is then applied to a single-cylinder spark-ignition engine fitted with both intake and exhaust manifold systems and also a carburettor.