Despite of simultaneous reduction of the nitric oxide (NO) and smoke emissions in a biogas-KME (Karanja methyl ester) fueled dual fuel engine, there seems to be lower efficiency, higher fuel consumption, and longer ignition delay period. In this study, an attempt has been made to increase the thermal efficiency, reduce the brake specific fuel consumption (BSFC) and reduce the ignition delay as much as close to that of diesel, in biogas-KME run dual fuel diesel engine, applying DEE port injection strategy. In KME-biogas-DEE operation, biogas was inducted through the intake manifold using a gas mixing kit and small quantity of DEE (2%, 4%, and 6%) was injected with the help of an electronic injector. In dual fuel mode, the KME injection timing was set at 24.5 degrees CA bTDC, while biogas was inducted at an optimum flow rate of 0.9 kg/h. The dual fuel operation of BDFM24.5/DEE4 (biodiesel biogas dual fuel mode with injection timing of 24.5 and DEE injection of 4%) gave better results in terms of the combustion, performance and emission characteristics, than those of other DEE injection cases. BDFM24.5/DEE4 gave an increase in BTE of 2.3% and reduction in BSFC of about 5.8% than that of BDFM24.5 at full load. A reduction in CO, HC, and smoke emissions of 12.2%, 10.6%, and 5.7% was observed for BDFM24.5/DEE4 in comparison with BDFM24.5, at full load respectively. But the NO emission for BDFM24.5/DEE4 was 12.7% higher than that of BDFM24.5, at full load. (C) 2015 Elsevier Ltd. All rights reserved.