This research aims to improve the combustion performance of gasoline-bioethanol fuel blended in the ratio of 50:50 (E50) on the spark-ignition engine by employing a new combustion strategy. The Box Behnken Design of Response Surface Methodology and Non-Linear Programming was employed to optimize the performance of the engine and create some engine parameters. The performance of the engine consists of power, torque, thermal efficiency, fuel consumption, and the emission of CO and HC, while the engine and combustion parameters are compression ratio, ignition timing, and engine speed. A new combustion strategy will be applied in this study with a tiered mapping process for each engine parameter based on the MBT. The brake torque increased by 13.5 % while HC and CO emissions decreased by 15 % and 71 % respectively when the combustion strategy applied if compared o the pure gasoline in engine standard condition. Furthermore, the BSFC increased by 33 % while BTE decreased by 15 % towards the gasoline fuel. The non-linear programming applied in this study intended to figure out the best combination of the engine parameters in obtaining optimum engine performances. In the RSM analysis, the codes --1, 0, 1 represented 12, 12.5, and 13 of compression ratio, 16, 20, and 24 BTDC of ignition timing and 2000, 5000, and 8000 rpm of engine speed. Therefore, 20 BTDC of ignition timing and 13:1 of compression ratio is the optimum engine parameters used in gaining the optimal performance of the engine when E50 runs in SI-PFI engine of 150 cm3

The first and second laws of thermodynamics analysis used to show the rate of energy and exergy as a performance of SI-PFI engine with the variation of fuel ignition between 10 and 26 BTDC (before top dead Centre) at interval 4 BTDC. The engine was performed on eight levels of speed in intervals 2000--8000 RPM (increment of 1000 RPM) with pure bioethanol fuel (E100) and 13:1 of compression ratio. The effect of fuel ignition on energy and exergy analysis of E100 fuel will be compared with E0 as reference fuel that performed in 11:1 of compression ratio and 10 BTDC. The results show that the maximum efficiency of energy and exergy for the E100 are 46.59 and 41.90 % at 18 BTDC and 6000 RPM. Meanwhile, the maximum efficiency of energy and exergy for E0 were 43.33 and 31.76 % at 5000 RPM. Moreover, the minimum BSFC for the E100 is 0.2867 kg/(kW•h) at 6000 RPM and 18 BTDC while for the E0 is 0.1960 kg/(kW•h) at 5000 RPM. These results indicate that E100 is more effectivein transferring heat into useful work although it is 30 % more wasteful than E0