Liquefied Petroleum Gas (LPG) and Compressed Natural Gas (CNG) have long been recognized as ideal clean and potentially available fuels for motor vehicles. However, some disadvantages of the two gaseous fuels such as lower energy density (kW/l) compared to gasoline, a loss of power in unmodified converted engines relative to gasoline and the current shortage of refueling stations hamper their widespread use. Additionally, engines with throttle-body gaseous fuel fumigation need longer cranking time and exhibit relatively slow response during transient engine operation.
To alleviate the above shortcomings, a low cost dual-fuel system was developed. The prototype system uses a mixture of gaseous fuel (Liquefied Petroleum Gas) and gasoline to enhance fuel economy, drivability, and lower emissions. The two fuels can be mixed at any percentage depending on the customer's need. The system uses proven gaseous fuel system components to deliver gaseous fuel and the original equipment manufacturer's (OEM) fuel injection system to provide gasoline. The gasoline injectors trim the total fuel demand. The dual-fuel system is designed for easy implementation.
Exhaust emissions and fuel economy of the gasoline baseline and the LPG/gasoline dual-fuel vehicle are presented. It was found that CO and HC emissions of the dual-fuel vehicle are lower than those of the gasoline baseline and LPG-dedicated baseline, and the NOx emissions are equal or slightly lower than that of the gasoline baseline. The fuel economy on gasoline equivalent energy basis of the dual-fuel vehicle is lower than that of the gasoline baseline and higher than the LPG-dedicated baseline vehicle.