The effects of ethanol fumigation (EF) on combustion, smoke index K and nitrogen oxides (NOx),) emission and performance parameters of a turbocharged IDI automotive diesel engine have been examined experimentally. Also, evaluations based on heat release and flammability analysis have been done. Experiments were performed at three diesel fuel delivery rates (FDRs), three different engine speeds and various EF ratios (EFRs). Ethanol was introduced into intake air by a carburetor, which main nozzle section is adjustable, given approximately 2%, 4%, 6%, 8%, 10% and 12% (by vol.) ethanol ratios. Experimental results show that smoke index K reduces for up to 4-8% EFRs but then it begins to increase. EF tests results showed that NOx emission takes lower values than that of neat diesel fuel (NDF). NOx emission decreases approximately 8.5%, 9.79% and 11.02% for 1/1, 3/4 and 1/2 FDRs respectively, at the selected engine speeds. For ethanol ratios higher than 8-10%, engine performance parameters improve for 1/1 and 3/4 FDRs but they deteriorate for 1/2 FOR at selected engine speeds. In heat release rate diagram two distinct peaks are observed for high ethanol additions. The first peak occurs before top dead center (TDC) and the second peak takes place after TDC. On the other hand, the first peak becomes larger, but the second peak diminishes as ethanol percentage increases. That is, premixed combustion of ethanol-air improves engine performance and also it increases in-cylinder pressure. However, total fuel cost of EF becomes higher than NDF because actual ethanol price is six times of diesel fuel in Turkey. (C) 2014 Elsevier Ltd. All rights reserved.