Power and Emission Evaluation of Natural Gas Engines Converted From Gasoline

In the present article, the performance analysis of a bi-fuel spark ignition engine is investigated. An originally gasoline-fuelled car is used for experimental tests. It is converted to a bifuel vehicle which may run both on natural gas and gasoline. The wheel and motor power of the car are measured before and after conversion together with exhaust emissions. It is observed that the engine power reduces not only in gas but also in gasoline state after the conversion in comparison with the base engine power. The effect of gas/air mixer design is fully explained. The results of closed-loop and open-loop gas supplying systems are compared. The influence of ignition timing on the power loss is discussed. The optimum timing advance for natural gas is obtained through laboratory experiments. The power and emissions of the converted vehicle are compared with the base power and emission values for a series of engine speeds. The reasons for the power loss are discussed and some useful methods are recommended to decrease the amount of power loss.