What does the term "stall speed" refer to in a torque converter?

• A. The RPM at which the engine operates efficiently
• B. The RPM at which the torque converter begins to deliver useful torque
• C. The maximum speed achievable during a stall
• D. The RPM at which the vehicle starts to move

Answer: (B)

The term "stall speed" in the context of a torque converter specifically refers to the RPM at which the torque converter starts to deliver useful torque. This is a critical parameter in the performance of automatic transmission systems. When the engine speed reaches the stall speed, the torque converter allows the engine to produce sufficient torque to overcome inertia and initiate vehicle movement. It represents the point at which the fluid couplings within the torque converter reach a state where they begin transmitting power from the engine to the transmission effectively, facilitating acceleration. This is particularly important for understanding how a vehicle responds under various loads and during start-up conditions.

Stall speed is influenced by factors such as the torque converter design, vehicle weight, and the engine's power characteristics, which all contribute to its effective performance and drivability. Understanding stall speed helps in optimizing vehicle performance and tailoring the driving experience based on engine and torque converter specifications.