In the present work, high free fatty acid (FFA) crude rice bran oil (CRBO) blend was tested in a stationary CI engine and investigation was focused to reduce NO emission than diesel with lesser smoke density. Combustion process was modified by varying the factors namely fuel injection timing, percentage EGR and fuel injection pressure in a combination suggested by Taguchi's L9 orthogonal array. Three levels were chosen in each factor and NO emission, smoke density and brake thermal efficiency were taken as the response variables. Multi response signal–to–noise (MRSN) ratio was calculated for the response variables and the optimum combination level of factors was obtained simultaneously using Taguchi's parametric design. Obtained optimum combination level was confirmed experimentally and significant improvement was observed in the response variables. [Received: June 20, 2011; Accepted: July 21, 2011]

Keywords: diesel engines, nitrogen oxide, NOx, smoke density, analysis of variance, ANOVA, multiresponse signal–to–noise, MRSN, Taguchi methods, orthogonal arrays, free fatty acid, crude rice bran oil, emission control, engine emissions, parameter design, vegetable oils, design of experiments, DOE, brake thermal efficiency, biofuels