This paper reviews a study of engine performance MODENAS CT15s by redesign internal geometry to improve flow pattern of air box. Air box is an empty chamber on the inlet of most combustion engines combustion process. It collects air from outside and feeds it to the intake hoses of each cylinder. The entire air box collects the fresh air and later gets it filtered through the air filter present inside it. Engine can be easily breathing related to flow pattern by best design of air box that can contribute to performance. Flow pattern of air box affect the volumetric efficiency, mass flow rate and velocity which ultimately makes impact up on the engine power & torque. 3D Computational Fluid Dynamics (CFD) analysis was carried out for an existing model and several improvement models to make comparison of air flow behaviour through the air box geometry. Based on the results, geometrical changes like sigle blade placement in inlet plenum showed good improvement in flow behaviour compare to existing model. By using 3D CFD analysis, the best design of the air box for a motorcycle engine is achieved with considerable reduction in development time and cost.
