What must a starting system continue to supply until the engine reaches a predetermined RPM?

The starting system is designed to provide torque to initiate and sustain the rotation of the engine until it reaches a specific RPM necessary for self-sustaining combustion. Torque is crucial during the engine's start sequence because it helps overcome inertia and friction within the engine components. Once the engine reaches the predetermined RPM, it can become self-sustaining, allowing it to continue running without additional external torque.

While other factors like fuel pressure, airflow, and electrical power are important for engine operation, torque is the primary requirement for the starting system to facilitate the initial engine startup. After the engine reaches the required RPM, the torque demand diminishes as the engine transitions to a running state and can maintain its operation independently. Therefore, the focus on torque specifically illustrates its role in ensuring that the engine successfully starts and achieves operational speed.