The analysis of the factors involved in transformation of energy in cycles piston internal-combustion engines is manufactured. The entroic method in an application to the analysis of a real cycle piston internal-combustion engines is circumscribed. The method implements additive link of a value of a display efficiency with coefficients of a loss and losses of an exergy. The method grounded on an entroic method, on a quantitative assessment of influence on a value of a display efficiency of thermodynamic conditions of transformation of energy is offered not only in view of a place of an application of heat in a cycle, but also place of an application in volume of a combustor.