Experiments were conducted at different loads including the rated load (4.4 kW) and over load (4.75 kW) for water–diesel emulsion and water injection. The water–diesel emulsion ratio of 0.4:1 was chosen for the study as it was found to be the optimum based on the author’s earlier research work [4]. The same water content (water–diesel ratio: 0.4:1 by mass) was maintained for both methods and the results are compared with base diesel. The detailed study of optimization of water–diesel emulsion may be referred in literature [4]. Water–diesel emulsion was prepared using a surfactant(HLB = 7) with help of emulsion preparation apparatus which is explained in Section 2.3 and the emulsion was injected into in-cylinder during compression stroke using the main injection system. In case of water injection, plain water was injected into intake manifold using an auxiliary injector which was controlled by an ECU. A static injection timing of 23 BTDC was kept as constant for all experimental tests. The performance and emission characteristics of the engine was measured for both methods and the results are compared with base diesel. The pressure-crank angle data was measured using piezo-electric transducer and TDC encoder and the data was given as input for calculating ignition delay,heat release rate and rate of pressure rise. The dynamic injec-tion timing was measured using a needle lift sensor and it was used for finding out ignition delay.