Study of Ethanol-Blended Fuel (E85) Effects Under Cold-Start Conditions

Research was conducted on cold startability with a focus on the vaporization characteristics of ethanol blended fuel (E85). Cold startability was tested with a conventional gasoline engine with standard calibration data by using gasoline and E85 of which RVP is adjusted to be equivalent to gasoline. The test engine started successfully when the gasoline was used, but failed to start when the E85 was used. A further analysis of this result indicated the fact that E85 displays lower vaporization than gasoline under cold conditions even if the RVP of both fuels are the same. The research determined that the formation of an air fuel mixture with minimum of 2 vol% fuel concentration is necessary for a successful engine start. The effects of increasing compression ratio and cranking speed as means of enhancing fuel vaporization were investigated and no major impacts ware observed. To enhance the fuel vaporization in a cold environment, two effective methods, increase of injected fuel quantity and usage of a high RVP fuel, were revealed through this research. To keep the same engine startability as the gasoline in a cold environment by using the E85 fuel (ASTM Class-3), about 3 times the quantity of fuel should be injected or RVP of E85 fuel should be adjusted to about 108 kPa. From this research it is concluded that to realize more efficient cold start in terms of fuel consumption, it is necessary to reconsider the RVP standard for cold conditions.