Sigh
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Pitot, It is not possible to increase the performance of the engine above flat rated temperatures, because there is no more performance available.
At full power settings the engine is guaranteed to produce a certain minimum thrust UP TO IN THE CASE OF THE CFM56 ON THE NG ISA + 15. above this temperature the thrust will DECREASE because of various engine parameter limitations. The engine may be EGT, N1 or N2 limited depending on the conditions of the day. The FMC 'knows' this so when a high assumed temperature is used it reduces thrust to the appropriate value to compensate. Thus helping ensure the engine does not over boost or over temp.