|The purpose of this study is to investigate the effect of ethanol volume fraction and engine speed on the combustion and exhaust emissions characteristics in a turbo-charged spark-ignition (SI) engine. The test engine has 1,998 cc of displacement volume, 9.4 of compression ratio, and 4-cylinders. The test fuels are E20, E40, E60, E80, E100, and G100. A brake torque was measured and analyzed for the combustion performance, and a NOx (nitrogen oxides)/CO (carbon monoxide) was measured. From the experimental results, it revealed that the increase of ethanol fraction caused the increase of brake torque, the decrease of NOx and CO emissions. In NOx and CO emissions, the increase of engine speed induced the increase of NOx and decrease of CO in general.