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In order to reduce tail-pipe hydrocarbon emissions from SI gasoline engines, rapid catalyst warm-up and improvement of catalyst conversion efficiency are important. There are many reports which have been published by manufacturers and research institutes on this issue. For further reduction of tail-pipe hydrocarbon emissions, it is necessary to reduce engine-out hydrocarbon emissions and to improve after treatment, during the time the catalyst is not activated. This paper quantitatively analyzed the fuel amount of intake port and cylinder wall-wetting, burned fuel and engine-out hydrocarbon emissions, cycle by cycle in firing condition, utilizing a specially designed analytical engine. The effect of mixture preparation and fuel properties for engine-out hydrocarbon emissions, during the cold engine start and warm-up period, were quantitatively clarified.

In SI engines with port injection system, fuel behavior both in the intake port and in the cylinder has significant influence on the transient A/F characteristics and HC emissions [1]. Therefore, to improve the engine performance, it is very important to understand fuel behavior in the intake port and in the cylinder [2, 3]. This paper describes the following three unique methods to analyze fuel behavior in port injected SI engines and some test results. (1) Observation of fuel behavior in the intake port, using a transparent intake air tube and a strobe synchronized TV-photographic system. (2) Observation of fuel behavior in the cylinder, using a glass cylinder and fluorescent fuel. (3) Measurement of fuel wall wetting in the intake port and in the cylinder, using the engine with electronically controlled hydraulically driven in-take/exhaust valves.