One dimensional model for a four cylinder V type turbocharged CNG engine has been developed and studied in detail using GT-POW ER software . The sensitivity analysis for a wide variety of parameters such as BMEP, BSFC, volumetric efficiency, turbocharger speed and compressor efficiency at different intake and exhaust of turbocharger unit conditions has been carried out for a specified engine with certain valve timings, injection timing and compression ratio at different engine speeds. For validation purposes the results are compared with experimental data available where 5 percent error has been achieved. The results obtained could be accurately used to predict and optimize a set of favorable performance conditions during SI engine development process and turbocharger selection also improved matching of parameters. GT-Power is a very powerful tool for simulating complete engines. However care must be taken when analyzing the results. The code only uses one direction and time, meaning that the flow will always be uniform in the cross sections. Whereas in many parts of the real engine the flow field is three dimensional and far from uniform in the cross-sections.