The objective of this work is to optimize the operating parameters of the Direct Injection Single Cylinder (5.2 kw) CI engine with respect to Brake Thermal Efficiency (BTE), Hydrocarbons (HC) and Carbon dioxide (CO2). For this investigation, we used Simarouba Biodiesel as an alternate fuel for diesel fuel which possesses low cetane number which is not sufficient to operate existing diesel engine. However, this could be combined with the diesel fuel in the form of blends. For this investigation four levels and four parameters were selected viz. Injection Pressure (IP), Fuel Fraction (FF), Compression Ratio (CR) and Injection Timing (Before TDC). Taguchi Method is used for minimizing the number of experiments and Multiple Regression Analysis is used to find the optimum condition. Three outputs variables such as; Brake Thermal Efficiency (BTE), content of HC particles and CO2 in the emission are measured and considered its influence on CI Engine performance. The test was carried out at full load condition and the optimized condition are found such as; 18:1 Compression Ratio, 250 bar Injection Pressure, 22° Injection Timing and 20% Fuel Fraction. The optimized condition gives better performance than diesel, HC emission is nearly similar as that for diesel fueled engine but CO2 slightly increases.