This chapter delves into the dynamic modeling of crankshafts in both single-cylinder and multi-cylinder internal combustion engines (ICEs), emphasizing the primary contributors to torque generation: gas pressure and inertia forces. In single-cylinder engines, where only one combustion event occurs per cycle, significant fluctuations in torque are a characteristic feature. These fluctuations are modeled using key equations that account for variables such as gas pressure, crankshaft angle, and inertia forces. In contrast, multi-cylinder engines distribute the combustion processes among multiple cylinders, resulting in smoother and more consistent torque output. Dynamic models for 3-cylinder, 4-cylinder, and 6-cylinder engines are analyzed, highlighting how the phasing and timing of firing events across cylinders reduce torque variability. This is achieved by strategically aligning the power strokes of different cylinders to minimize gaps in torque delivery. A detailed comparative analysis of instantaneous torque values at engine speeds of 3200 RPM and 5400 RPM underscores the changing dynamics of torque generation. At lower engine speeds, gas pressure is identified as the dominant factor influencing torque. However, as engine speeds increase, inertia forces become the primary contributor due to the higher acceleration and deceleration of moving components. The study further reveals that the number of cylinders and the engine speed significantly impact the torque characteristics. Among the configurations studied, 6-cylinder engines demonstrate the smoothest torque curve, offering superior performance by effectively reducing torque acyclism. This leads to enhanced engine stability and improved operational reliability under varying load and speed conditions. Such insights underline the critical role of cylinder count and engine speed in optimizing engine design and performance.