Biodiesel is a methyl or ethyl ester of fatty acids made from vegetable oils and animal fat. It can be used in diesel engines with very little or no engine modifications. In this present work the experimental investigations are carried out on the test engine operated with methyl esters of sesame oil and diesel blends and also by using ignition improver as an additive. Comparative measures of performance parameters, smoke opacity, unburned hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx) and carbon dioxide (CO2) emissions were calculated. In the initial stage the tests were conducted on the four stroke single cylinder water cooled direct injection diesel engine by using diesel at various loads and base line data was generated. In the second stage, tests were carried out using methyl esters of sesame oil with diesel blends at same operating parameters and compared with the base line data obtained earlier. Engine performance in terms of higher brake thermal efficiency and lower brake specific fuel consumption and lower emissions (HC, NOx) were observed for 20% sesame oil and 80% diesel and it is chosen as optimum blend. Then after for above optimum blend in the third stage the tests were conducted again on the engine to find out the performance and emission parameters by adding ignition improver DEE (Diethyl Ether) in the proportions of 0.5% and 1%. Finally the performance and emission parameters obtained by adding DEE were compared with the optimum blend and it has been observed that no change in BTH and further reduction in emissions like HC, smoke opacity, NOx are observed.