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This paper describes an experimental study of the effects of ignition spark characteristics on combustion behaviour in a light duty automotive engine. A prototype programmable energy ignition system was used to investigate the influence of both spark energy and the current/time profile used to deliver a given amount of energy. The engine was tested under part load conditions using a stoichiometric air/fuel ratio and relatively high levels of exhaust gas recirculation (EGR). In addition to tests with port-injected gasoline, tests were also carried out using propane (premixed upstream of the throttle) in order to investigate the possibility that improvements in the homogeneity of the mixture might influence the impact of varying the spark characteristics.

This study describes the design and proof-of-concept testing of a system which has enabled sub-zero cold starting of a port-injected V6 engine fuelled with M100. At -30°C, the engine could reach running speed about 5s after the beginning of cranking. At a given temperature, starts were achieved using a fraction of the mixture enrichment normally required for the more volatile M85 fuels. During cold start cranking, firing is achieved using a high energy plasma jet ignition system. The achievement of stable idling following first fire is made possible through the use of an Exhaust Charged Cycle (ECC) camshaft design. The ECC camshaft promptly recirculates hot exhaust products, unburnt methanol and partial combustion products back into the cylinder to enhance combustion. The combined plasma jet/ECC system demonstrated exceptionally good combustion stability during fast idle following sub-zero cold starts.

The temperature and pressure of the charge, reached at the end of the compression stroke when an engine is cranked for starting, decide whether it will start and attain selfsustained running. These, in turn, are affected by the crevice volume in, and the blowby from, the engine, particularly at cold ambient temperatures and low cranking speeds. This paper presents a model to estimate these effects. Tentative values are proposed for the parameters that appear in the model based on experiments performed on small engines motored in a cold chamber. The model can be incorporated in engine cycle simulation programs to allow for crevice and blowby effects. It is impossible to prevent gas leakage entirely from an operating reciprocating engine. Gas may leak at the valves, the cylinder head gasket, the spark plug gasket, the injector gasket and the piston rings. The gas that leaks from the cylinder past the piston rings into the crankcase is termed “blowby”.

Geometric maldistribution is recognized as a major impediment to obtaining maximum efficiency from carbureted or single point injected methanol fuelled engines. In this program engine tests have been conducted with the inlet manifold inclined to provide a gravitational influence on the flow of fuel in order to study maldistribution effects due to manifold fuel films. It was found that substantial distribution errors were caused by this slight gravitational influence, which was only a fraction of that which could occur periodically in a maneuvering passenger car. Improved atomization is shown to be superior to heating the inlet air for reducing maldistribution, although the latter vaporized fuel more completely before the inlet ports. Fuel films may evaporate more easily than airborne droplets in the size range produced by many carburetors.