Comparative Studies on the Idling Performance of a Three Cylinder Passenger Car Engine Fitted with a Carburettor and a Single Point Electronic Gasoline Fuel Injection System

Experimental investigations relating to the performance and emission characteristics under idling conditions of a three cylinder passenger car spark ignition engine operating on a conventional carburettor and a developed single point gasoline fuel injection system are described in this paper. The idling performance at different engine speeds was studied by carrying out comprehensive engine testing on a test bed in two phases. In the first phase, experiments were conducted on an engine fitted with a conventional carburettor whilst they were extended to the engine provided with a developed electronic single point fuel injection (SPI) system, whose fuel spray was directed against the direction of air flow. The injection timing of the SPI system was varied from 82 deg. before inlet valve opening (or 98 deg. before top dead center) to 42 deg. after inlet valve opening (or 26 deg. after top dead center). An injection timing of 42 deg. before inlet valve opening (or 58 deg. before top dead center) was observed to be optimum. As compared to the carburettor version, SPI system operation under idling conditions resulted in :- 1 Lower cylinder to cylinder variation in mixture strength. 2 Less cyclic variations. 3 Stable operation under a leaner air fuel ratio. 4 Improved fuel consumption. 5 Lower level of carbon monoxide and hydrocarbon emissions.