Abstract
The application of natural gas for vehicles particularly public transportation such as taxi has been introduced by Indonesian government since 1988 however the result is still unsatisfactory. One of the reason is the drivability of natural gas vehicle is slightly lower than gasoline vehicle particularly concerning the changeability from natural gas to gasoline or vice versa, slow acceleration and lower poser. This work based on two important factors:1. The ignition timing must be re-set in order to achieve the optimal performance when the fuels are changed. 2. During the interchange phase of between fuels the engine tends to stall or even to stop since the mixture of fuel-air is too rich. Laboratory of International Combustion Engines and Propulsion Systems, Institute Technology Bandung, Indonesia has developed a simple and low cost solution to improve the performance and comfort of dual fuel engines. The systems is working when the fuel is changed by automatically turning the ignition distributor in order to re-set the ignition timing and controlling opening time of gasoline and natural gas valve bases on duration of changing between both fuel in the carburetor. The results showed that the ignition timing can be set automatically in order to achieve the optimal performance for each fuel with minimum efforts from the driver and the changing process of fuels can be accomplished smoothly, the engine doesn't tend to stall or to stop. The system showed very satisfactory results and quite simple to implement.