Engine efficiency is one of the key aspects to reduce CO2 emissions. In order to improve the emission maintaining high performance capabilities several devices are introduced in the system; variable valve timing technology allows more flexibility for modern engines to meet peak performance, fuel economy and low emissions targets while providing good driveability. This paper describes the Lamborghini continuously-variable cam phaser model using a graphical technique, called Power Oriented Graphs (POG), that uses an energetic approach for representing the physical systems. The generally accepted approach is to calibrate an engine on a dynamometer and to adjust the operation of the engine to meet performance targets. With the current build and test approach, these adjustments may not be made until well into the development program, and this calibration is a costly and time consuming step in the engine development process: the main purpose of this works is allowing a faster model's calibration time. Furthermore the usefulness to model the system consists of analyzing in simulation many more system configurations than those available for real experiments so it's important using a simple methodology that is able to analyze the whole system's dynamic in order to reach the performance expectations. The results obtained were validated demonstrating the effectiveness of the POG technique.