Abstract: The study of effect of injection timing along with engine operating parameters in Jatropha biodiesel engine is important as they significantly affect its performance and emissions. The present paper focuses on the experimental investigation of the influence of injection timing, load torque and engine speed on the performance, combustion and emission characteristics of Jatropha biodiesel engine. For this purpose, the experiments were conducted using full factorial design consisting of (3(3)) with 27 runs for each fuel, diesel and Jatropha biodiesel. The effect of variation of above three parameters on brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), peak cylinder pressure (P(max)), maximum heat release rate (HRR(max)), CO, HC, NO emissions and smoke density were investigated. It has been observed that advance in injection timing from factory settings caused reduction in BSFC, CO, HC and smoke levels and increase in BTE, P(max), HRR(max) and NO emission with Jatropha biodiesel operation. However, retarded injection timing caused effects in the other way. At 15 N m load torque, 1800 rpm engine speed and 340 crank angle degree (CAD) injection timing, the percentage reduction in BSFC, CO, HC and smoke levels were 5.1%, 2.5%, 1.2% and 1.5% respectively. Similarly the percentage increase in BTE, P(max), HRR(max) and NO emission at this injection timing, load and speed were 5.3%, 1.8%, 26% and 20% respectively. The best injection timing for Jatropha biodiesel operation with minimum BSFC, CO, HC and smoke and with maximum BTE, P(max), HRR(max) is found to be 340 CAD. Nevertheless, minimum NO emission yielded an optimum injection timing of 350 CAD. (C) 2011 Elsevier Ltd. All rights reserved.