Difference between revisions of "Horsepower"

'''Indicated horsepower''' is the theoretical power of a reciprocating engine assuming that it is completely efficient in converting the energy contained in the expanding gases in the cylinders.  It is calculated from the pressures developed in the cylinders, measured by a device called an ''engine indicator'' - hence indicated horsepower. It was the figure normally used for steam engines in the 19th century but is misleading because the mechanical efficiency of an engine means that the actual power output may only be 70% to 90% of the indicated horsepower.