The aim of this study is to investigate the effects of dimethyl ether (DME) fuel on the engine performance and the exhaust emission reduction characteristics in a DME fueled four-cylinder diesel engine with a common rail injection system, as well as an injection characteristics and a spray behavior. The injection rate meter and the spray visualization system are utilized for the analysis of the injection characteristics and the spray behavior. Also, the modified four-cylinder diesel engine with 1.6 liter engine size is used for the investigation of the engine performance and the exhaust emission reduction characteristics of DME fuel. Based on the experimental investigation, it revealed that the injection quantity of DME fuel was larger than that of the ultra low sulfur diesel (ULSD) due to the high return fuel pressure at the same injection pressure and energizing duration. In this case, the injection quantity of DME fuel is increased by extension of real injection duration due to return fuel pressure. In combustion characteristics, the peak combustion pressure and the ignition delay of DME fuel are higher and faster than those of ULSD, respectively. The NO emission of DME fuel shows slightly higher than that of ULSD at the same engine load condition, and the soot emission of DME fuel is nearly zero level. The oxygenated component and volatility of DME resulted in HC and CO emissions that were lower than those of diesel. (C) 2011 Elsevier B.V. All rights reserved.