In Motorsports the understanding of the real engine performance within a complete circuit lap is a crucial topic. On the basis of the telemetry data the engineers are able to monitor this performance and try to adapt the engine to the vehicle's and race track's characteristics and driver's needs. However, quite often the telemetry is the sole analysis instrument for the Engine-Vehicle-Driver (EVD) system and it has no prediction capability. The engine optimization for best lap-time or best fuel economy is therefore a topic which is not trivial to solve, without the aid of suitable, reliable and predictive engineering tools. A complete EVD model was therefore built in a GT-SUITE™ environment for a Motorsport racing car (STCC-VW-Scirocco) equipped with a Compressed Natural Gas (CNG) turbocharged S.I. engine and calibrated on the basis of telemetry and test bench data. The driver is simulated by means of a "position based" control in order to determine the braking points at each corner by itself and regulate the braking/accelerating intensity. By means of simplified vehicle dynamics and a complete engine flow dynamic modeling the behavior of the overall system during the lap can be analyzed and different scenarios simulated. In particular the focus is concentrated on the real operating conditions of the powertrain unit, which can be eventually combined also with energy recovery systems (e.g., KERS and TERS). In the proposed EVD model each technical element (Engine, Vehicle) is distinct and can be interchangeable. For example, the engine can be virtually optimized and the influence of different technical configurations or engine mapping on the global performance can be investigated. The aim is to create modeling solutions which are compatible with the short development time of motorsports and thus to maintain acceptable CPU-time. As results of the proposed simulations show, spark advance, fuel injection and direct control of the waste-gate (WG) are parameters which can influence the overall performance for the adopted racing vehicle.