How is engine torque calculated?

There are mainly two methods for calculating engine torque. At the basic physics level, it can be calculated by the product of force and moment arm, with the formula: Torque M = Force F × Moment Arm r (where F is the force acting perpendicularly on the moment arm, in Newtons; r is the length of the moment arm, in meters; the resulting unit is Newton-meters, Nm). In automotive engineering, the commonly used calculation method is based on the engine's output power and rotational speed, with the formula: Torque T = 9550 × Power P ÷ Rotational Speed n (where P is the output power, in kilowatts, kW; n is the rotational speed, in revolutions per minute, rpm). For example, an engine with a power of 100 kW and a rotational speed of 5000 rpm has a torque of 9550 × 100 ÷ 5000 = 191 Nm. Torque is widely used in the automotive field. During the design phase, it can be used to optimize the parameter matching of the engine, transmission, and drive system by calculation, and select an appropriate gear ratio to balance power and fuel economy. In performance testing, the torque curve can reflect the dynamic characteristics of the engine and help evaluate the power transmission efficiency. In the manufacturing process, parts assembly must strictly follow torque requirements. For instance, the bolt tightening torque should be moderate to avoid loosening or damage, ensuring the reliability and stability of the vehicle.