In this study the combustion, performance and emission parameters of single cylinder, four stroke, constant speed diesel engine operating on diesel oil and different blends of soybean methyl ester (SME) have been investigated experimentally and also theoretically using the simulation software Diesel-rk. It was found that 25.27%, 36.93%, and 52.96% reduction in the Bosch smoke number is obtained with B20% SME, B40% SME and B100% SME respectively, as compared to pure diesel fuel. All blends of biodiesel are observed to emit higher NOx emissions relative to that of nominal diesel level. The results point out that B20% SME was the best one which gives little performance differences with good reduction in emissions when compared to diesel fuel. Different strategies are adopted to control biodiesel NOx effect on the B20% SME. From the one dimensional strategy it is observed that cooling air temperature from (55 to 15) degrees C reduce NOx, air pollutant emissions (SE), Bosch smoke number and brake specific fuel consumption (BSFC) by 10.53%, 17.63%, 2435%, and 6.2% respectively with respect to base line operation. Deeper piston bowel with small diameter gives a significant reduction in the NOx emissions. According to scanning 2-dimensional strategy it is found that the best reduction in the NOx, air pollutant emissions and Bosch smoke number is 22.84%, 20.2%, and 8.31% respectively while BSFC is increased by 5.14% at 19 compression ratio and 0.06 exhaust gas recirculation ratio (EGR). A multiparametric optimization technique using Rosenbrok method for diesel engine operating on B20% SME was investigated theoretically. The optimization gives 50.26% reduction in NOx emissions. The theoretical simulation results are verified with the experimental study conducted at the same operating conditions. (C) 2013 Elsevier Ltd. All rights reserved.