An experimental study of CNG/gasoline bi-fuel vehicle with one-ECU control

In this study, a new compressed natural gas (CNG) supply system was developed based on single electronic control unit (ECU) for a CNG/gasoline bi-fuel vehicle. To achieve low-level engine emission, the control strategies for air to fuel ratio and density compensation were formulated. The fuel switching control method is further discussed for the retrofitted bi-fuel vehicle to operate smoothly. A bench test was performed to calibrate the original gasoline engine´s emission performance with the developed control algorithm. A series of field tests were further performed with the retrofitted bi-fuel vehicle in different areas. The test results demonstrated that the main emission indexes of the CNG/gasoline bi-fuel vehicle with the single ECU´s control were lower than the threshold values issued by Chinese National Standard (GB 18352.3-2005) and the vehicle was able to operate smoothly when switching the fuel between CNG and gasoline.