Is fast acceleration determined by horsepower or torque?

[McVera]

Fast acceleration is determined by torque. Horsepower often determines the top speed. The relationship between torque and horsepower is that, under a fixed power condition, torque is inversely proportional to the engine speed. This means that at a certain speed, the greater the torque, the more power can be unleashed. Engine torque refers to the moment output from the crankshaft end of the engine. Under a fixed power condition, it is inversely proportional to the engine speed—the faster the speed, the smaller the torque, and vice versa. In physics, torque is the magnitude of the moment, equal to the product of force and the lever arm, with the international unit being Newton-meters (Nm). Maximum torque generally occurs in the mid to low-speed range of the engine, and as the speed increases, the torque tends to decrease.