Powertrain vibrations is a great concern in the automotive industry, once they are related to many Noise, Vibration and Harshness (NVH) phenomena. These are very complex system once their dynamic behaviour, in many cases, involve the interaction between the combustion engine and the remaing components of the powertrain, such as the clutch, transmission, differential, etc. In this work a system approach is used. First, the torque generated by a four cylinder engine is obtained through the thermodynamic equations. Then, these torque curves for each cylinder are combined and used as the excitation of a simplified model of a front wheel drive powertrain. Finally, the influence of ignition angles on the combustion characteristics and on the order content of engine output torque is analyzed. Results show that significant changes may happen on the second and fourth order responses.