This paper investigates the effects of glycerol ethoxylate as an ignition improver on injection and combustion characteristics of hydrous ethanol under a Cl engine condition. Injection characteristics were investigated by an in-house injection rate measurement device based on the Zeuch method, while spray combustion has been performed in the rapid compression and expansion machine (RCEM). The Cl engine condition indicated as density, pressure and temperature of compressed synthetic gas, consisting of 80% argon and 20% oxygen, at fuel injection timing in RCEM 01 21 kg/m(3), 4.4 MPa and 900 K. respectively. This condition is equivalent to the isentropic compression of air of the actual CI engine with compression ratio of 22. Hydrous ethanol without ignition improver (Eh95) and the ethanol dedicated for heavy duty vehicles (ED95: composed of hydrous ethanol with the commercial additive for ED95) are reference fuels representing low and high quality ethanol fuel for Cl engines, respectively. All test fuels are injected at constant heat input. The results indicate that the additional ignition improvers change injection characteristics, i.e. injection delay, injection rate and discharge coefficient of hydrous ethanol. The maximum injection rates at fully opened needle for the ethanol dedicated for heavy duty vehicles (ED95) and hydrous ethanol with 5% glycerol ethoxylate (5%GE) are lower than that of hydrous ethanol without ignition improver (Eh95) by approximately 10%. Additional injection duration is required for ED95 and 5%GE to maintain a constant energy input. Ignition delay and heat release rate of Eh95 are significantly improved by ignition improvers. The effect of ignition improvers on flame temperature is minor. KL factor, which is approximately proportional to soot amount in the optical path, and the measured soot emission, are affected by these improvers. (C) 2015 Elsevier Ltd. All rights reserved.