In this work, a dual-injection combustion mode for diesel n-butanol dual-fuel, combined direct injection (DI) of diesel with port fuel injection (PFI) of n-butanol, was introduced. Effects of n-butanol fraction, EGR rate and injection timing on this mode were studied on a modified single-cylinder diesel engine at the speed of 1400 r/min and the IMEP of 1.0 MPa. The results indicate that with increased EGR rate, NOx emissions reduce, but smoke emissions increase. As n-butanol fraction is increased, smoke emissions decrease with a small increase in NOx. However, higher HC and CO emissions, higher indicated specific fuel consumption (ISFC) and lower indicated thermal efficiency (ITE) have to be paid with increased n-butanol fraction, especially at high EGR condition. Advancing diesel injection timing suitably has the capacity of mitigating those costs and further decreasing smoke emissions with a small penalty in NOx emissions. Coupling of large butanol fraction, high EGR rate, and advanced injection suitably contributes to a better balance between emissions and efficiency in the diesel n-butanol dual-injection engine. (C) 2014 Elsevier Ltd. All rights reserved.