  In a previous paper we have shown that Newton's third law cannot strictly
hold in a distributed system of which the different parts are at a finite
distance from each other. This is due to the finite speed of signal propagation
which cannot exceed the speed of light at vacuum, which in turn means that when
summing the total force in the system the force does not add up to zero. This
was demonstrated in a specific example of two current loops with time dependent
currents, the above analysis led to suggestion of a relativistic engine. Since
the system is effected by a total force for a finite period of time this means
that the system acquires mechanical momentum and energy, the question then
arises how can we accommodate the law of momentum and energy conservation. The
subject of momentum conversation was discussed in a previous paper, while
preliminary results regarding energy conservation were discussed in previous
papers. Here we give a complete analysis of the exchange of energy between the
mechanical part of the relativistic engine and the field part, the energy
radiated from the relativistic engine is also discussed. We show that the
relativistic engine effect on the energy is 4th-order in 1/c and no lower order
relativistic engine effect on the energy exist.
