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The horizontal axis shows the rotational speed (in rpm) that the crankshaft is turning, and the vertical axis is the torque (in newton-metres) that the engine is capable of providing at that speed. Torque forms part of the basic specification of an engine: the power output of an engine is expressed as its torque multiplied by the angular speed ...
The torque is then related to the lever length, shaft diameter and measured force. The device is generally used over a range of engine speeds to obtain power and torque curves for the engine, since there is a non-linear relationship between torque and engine speed for most engine types. Power output in SI units may be calculated as follows:
Engine power is the power that an engine can put out. It can be expressed in power units, most commonly kilowatt, pferdestärke (metric horsepower), or horsepower.In terms of internal combustion engines, the engine power usually describes the rated power, which is a power output that the engine can maintain over a long period of time according to a certain testing method, for example ISO 1585.
Power in mechanical systems is the combination of forces and movement. In particular, power is the product of a force on an object and the object's velocity, or the product of a torque on a shaft and the shaft's angular velocity. Mechanical power is also described as the time derivative of work.
As piston engines usually have their maximum torque at a lower rotating speed than the maximum power output, the BMEP is lower at full power (at higher rotating speed). If the same engine is rated 72 kW at 5400 min −1 = 90 s −1, and its BMEP is 0.80 MPa, we get the following equation: =
The useful power of this linear motor is =, being the power, the useful voltage (applied voltage minus back-EMF voltage), and the current. But, since power is also equal to force multiplied by speed, the force F {\displaystyle F} of the linear motor is F = P / ( V K v ) {\displaystyle F=P/(VK_{\text{v}})} or F = I / K v {\displaystyle F=I/K ...
The useful power of an engine with shaft power output can be calculated using a dynamometer to measure torque and rotational speed, with maximum power reached when torque multiplied by rotational speed is a maximum. For jet engines the useful power is equal to the flight speed of the aircraft multiplied by the force, known as net thrust ...
Due to increasing vibration and heat, an external RPM limitation may also be installed. Power is the product of torque multiplied by speed of rotation (analogous to force multiplied by speed in a linear system), so peak power is produced in the upper speed range where there's both high torque and high RPM.