Power band

A mechanical transmission with a selection of different gear ratios is designed to make satisfactory power available over the full range of vehicle speeds.

A narrow power band is often compensated for by a power-splitting device such as a clutch or torque converter to efficiently achieve a wide range of speeds.

A continuously variable transmission can also avoid the issues of a narrow power band by keeping the engine running at an optimal speed.

In typical combustion engines found in vehicles, the torque is low at idling speed, reaches a maximal value between 1,500 and 6,500 RPM, and then falls more or less sharply toward the redline.

Above this speed several factors start to limit the torque, such as growing friction, the required time for closing the valves and combustion, and insufficient intake flow.

Such high speeds are reached by using lightweight pistons and connecting rods with short strokes to reduce inertia, and thus stresses on parts.

Therefore, the manufacturer's (or purchaser's/modifier's) choice of gearing, and appropriate use of the available ratios, is even more crucial to make best use of the available power and avoid being "bogged down" in flat spots.

Gas turbines operate at extremely high RPM by comparison, and exhibit narrow powerbands, and poor throttleability and throttle response.