Indicator power trial

An indicator power trial measures the indicated power of a reciprocating engine from the in-cylinder pressure-volume diagram taken during the sea trial. A mechanical indicator or electronic pressure transducer records the cylinder pressure through the stroke; the enclosed area of the p-V loop gives the indicated mean effective pressure, and IMEP times swept volume times rpm times cylinder count gives the indicated power. The difference between indicated and brake power measured at the shaft is the mechanical friction loss. The trial confirms balanced cylinder loading, peak pressures within the maker’s limit, and the indicated SFOC against the shop test, and flags a fuel-pump or injector fault as a low-power or high-Pmax cylinder.