An experimental study was conducted in a port fuel-injection, spark-ignition engine fuelled with blends of gasoline and n-butanol at different spark timings and EGR rates. The effect of spark timing, blend ratio and EGR rate on the emission characteristics (unburned hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide (NOx) and particulate size and distribution) was analyzed. BSFC (Brake specific fuel consumption) and MBT (maximum brake torque timing) at full load were also discussed. Results show that the blends of gasoline and n-butanol decrease engine specific HC, CO and NOx emissions compared to those of gasoline. Pure n-butanol increases engine specific HC and CO emissions and decreases NOx and particle number concentration compared to those of gasoline. n-Butanol addition can decrease particle number concentration emissions compared with that of gasoline. Advancing spark timing increases engine specific HC, NOx emissions and particle number concentration while it decreases engine specific CO emissions. EGR can reduce engine specific NOx emissions and particle number concentration simultaneously in spark-ignition engine fueled with gasoline and n-butanol blends. (C) 2011 Elsevier Ltd. All rights reserved.