e will only consider the case of a one-cylinder engine (but the model we use could have more inertias and torques added to model additional cylinders) and will use the following model, where 1 represents the inertia of the fly wheel, 2 the inertia of the crankshaft, and the spring the torsional flex in the crankshaft. Here represents the torque exerted on the crankshaft by the piston arm