How to find engine efficiency

How to find engine efficiency

To find the efficiency of any engine, find the relation performed by it works to the energy spent for it. Two main types of the engines used by the person – the internal combustion engine and the electric motor are known. Measuring the efficiency of the first, divide useful work into the general warmth which is marked out at fuel combustion, and for the second count the electric power spent for performance of useful work and find their relation.

It is required to you

  • characteristics of the internal combustion engine, cargo of the known weight and tester.


1. Determination of efficiency of the engine internal you sgoraniyanaydit the power of this internal combustion engine in technical documentation. Fill in in it fuel, it can be gasoline or diesel fuel, and force to work some time which measure by means of a stop watch, in seconds on the maximum turns. Merge the remains and determine the volume of the burned-down fuel, having taken away final from initial volume. Find its weight, having increased the volume transferred to m³ by its density in kg/m³.

2. For determination of efficiency increase engine capacity by time and divide into the work of mass of the spent fuel on its specific heat of combustion of KPD=R·t/(q•m). To receive result as a percentage, increase the turned-out number by 100.

3. If it is necessary to measure car engine efficiency, and its power is unknown, but weight is known, for definition of useful work disperse on it from a condition of rest to the speed of 30 m/s (if it is possible), having measured the mass of the spent fuel. Then increase the mass of the car by a square of its speed, and divide into the doubled work of mass of the spent fuel on the specific heat of its combustion of KPD=M • v \/(2 · q•m).

4. Determination of efficiency of the electric motor If electric motor power is known, then connect it to a current source with the known tension, achieve the maximum turns and a tester, measure current in a chain. Then divide power into the work of current and tension of KPD=R / (I•U).

5. If engine capacity is unknown, attach a pulley to its shaft, and lift on the known height, cargo of the known weight. Measure by a tester tension and current on the engine, and also load lifting time. Then divide the work of mass of cargo on height of rise and number 9.81 into the work of tension, current and time of rise in seconds of efficiency of =m • g•h/(I· U·t).

Author: «MirrorInfo» Dream Team