Conversion Into Energy

These percentages show the efficiency of the motor. They are the relation between the energy provided in the crankshaft and the energy produced in the pistons. The difference is lost as heat. In other words, efficiency is a relation between the output-energy and the incoming-energy . This is in according with the principles of Thermodynamics and because it's impossible to avoid heat losses there aren't any machines capable to operate at 100% of efficiency.

Motors are tested under laboratory conditions where compression rates are measured and calculated as energy amounts and compared with the output energy measured in the crankshaft.

To test electric motors incoming energy is simply the electric energy provided to the motor.