The purpose of this paper is to investigate the effects of blending ratio of Karanja oil methyl ester (KOME) on spray characteristics and to analyze the engine performance and exhaust emissions of Karanja bio-diesel blend vis-a-vis baseline diesel. Spray characteristics were analyzed using injection rate and spray visualization experiments for the following injection pressures: 50, 100 and 150 MPa. Engine performance, emission and combustion characteristics were also investigated at various engine operation conditions. From a comparison of the spray evolution of Karanja biodiesel 40% (v/v) blend (KB40) vis-a-vis baseline diesel, the spray shape revealed a narrower and deeper penetrating spray development process for KB40. However, at an ambient pressure of 4 MPa, which is considered to be similar to the cylinder pressure of a test engine, KB40 exhibited a spray evolution behavior (spray penetration and shape) closely resembling that of diesel. In the engine experiment, lower max torque, brake thermal efficiency (BTE) and exhaust gas temperature, in addition to higher brake-specific fuel consumption (BSFC) were observed for biodiesel blend compared to diesel due to lower heating value of Karanja biodiesel. (C) 2016 Elsevier Ltd. All rights reserved.