From the energy security and CO2 discharge reduction point of view, much attention has been paid to the usage of biofuel, ethanol, as an alternative source of energy in the transportation industry. Yet, the major drawback in applying highly concentrated ethanol in the spark ignited internal combustion engines is cold start instability. This is due to the characteristics of ethanol, large latent heat required to vaporize.
This paper investigates necessary conditions for the engine cold start, using highly concentrated ethanol. Tests performed with varieties of ethanol fuel, a relationship between cold startability lower temperature limit and reid vapor pressure was observed.
A method to boost the vaporization, intake valve timing control is introduced to obtain high compression peak temperature. The impact of controlling the valve timing on raising the compression peak temperature, the relationship between the compression peak temperature and cold startability, the ingredients of gasoline and ethanol mixture contributing to the engine, are analyzed quantitatively.