The present investigation explores the possibility of using Karanja methyl ester (KME) as a pilot fuel in a biogas run direct injection (DI) diesel engine of rated power 4.4 kW at 1500 rpm, with compression ratio of 17.5:1. The biogas was inducted with the intake air, and KME was injected directly into the combustion chamber. The injection timing of the pilot fuel, in the biodiesel dual fuel mode (BDFM) was varied from 21.5 degrees CA bTDC to 27.5 degrees CA bTDC in steps of 1.5 degrees CA. The BDFM with injection timing was denoted as BDFMX, where X indicates the injection timing. BDFM24.5 (biodiesel dual fuel mode of 24.5 degrees CA) gave better performance and lower emissions than those of other injection timings. The results showed that, the brake specific fuel consumption (BSFC) for BDFM24.5 was found to be higher by about 23.9% than that of KME, at full load. About 6.6% increase in the brake thermal efficiency was observed for BDFM24.5 in comparison with BDFM23.0, at full load. BDFM24.5 gave a reduction in the CO, HC and smoke emissions of 17.1%, 18.2% and 2.1%, in comparison with the BDFM23.0, at full load, respectively. But, the NO emission for BDFM24.5 was higher by about 5.5% than that of BDFM23.0, at full load. (C) 2016 Elsevier Ltd. All rights reserved.