Study of CNG Fueled Two-Wheeled Vehicle with Electronically Controlled Gas Injection System

Owing to its combustion characteristics and chemical composition, natural gas features cleaner emissions and lower CO₂ compared to gasoline under equal thermal efficiency. Natural gas can be a promising alternative energy source to respond to crude oil exhaustion and global warming issues. Focusing on the utility of natural gas, a feasibility study on CNG (Compressed Natural Gas) -fueled two-wheeled vehicles has been conducted. A proto-type two-wheeled vehicle was made based on a 125 cm³ class gasoline-fueled scooter. To adapt the engine to the use of CNG fuel, an electronically controlled gas injection system was applied to the fuel supply system. To provide abrasion resistance of engine valves and valve seats, the specific matter of gas-fuel was improved. Furthermore, a lubricant circulation passage was added to maintain the temperature of the pressure reducing valve. Environmental performance, which decreases CO by 90% and HC by 64% without after-treatment of exhaust gas, and decreases CO₂ by 33% in CO conversion equal to CNG with after-treatment of exhaust gas, was proved through this study. Considering the use of a BI-FUEL system, anti-abrasion measures for carburetor float valve and the selection of ignition plug become very important.