Abstract— The initial variations were pre-requisite in the internal-combustion engine, such as piston, exhaust, manifold for attaining effective torque, power and productivity. Moreover, it is also used for lessening poisonous gases of emission. These factors were the cause for enhancement of engine performance. The intent of intake manifold is disseminating the combination of air fuel equally over entire cylinders. Here, the objective of this manuscript is designing intake-manifold & examine the fuel injection position impact and mixture of air fuel on CNG SPFI performance. Here, modeling intake manifold is done by utilizing reverse data engineering. The multiple systems have been examined for deflection as well as stress. Moreover, the mixture of air-fuel has been assessed by utilizing analysis of computation fluid dynamics on the basis of uniformity index through changing location of injection. Furthermore, the turbulence impact was depicted by k turbulence method. Here, the performance of engine has been predicted by utilizing 1D experimentation software, where their outcomes have been compared to simulation outcomes.