A nonlinear model of a spark-ignited internal combustion engine for the design and simulation of idle speed controllers is presented. Due to the torque-based software architecture of modern engine control systems, the model incorporates the underlying physical relationships as well as parts of the engine control software functions. All parameters for the engine model are provided. The control inputs are the throttle command signal and the spark advance control signal. As output signals, the engine speed and the torque reserve are used. The suitability of this model for controller design is shown through an exemplary MIMO H design.