all load conditions at the same time in preferred embodiments the recuperator inlet temperature is prevented from exceeding its maximum allowable value at all operating conditions and the efficiency of the engine is optimized via simultaneous control of the recirculated exhaust gas flow rate and fuel air ratio it will be appreciated that the same system and method can compensate for changing ambient temperature thus as ambient temperature decreases the proportion of recirculated exhaust gas can be increased if necessary to maintain the needed combustor inlet temperature the combined effects of changing load and ambient temperature can also be compensated for by the system and method of the invention fig3 shows a second embodiment of the invention generally similar to that of fig2 except the valve 40 is located upstream of the recuperator 22 instead of downstream the line 42 thus bypasses the recuperator so the exhaust gas is not cooled in the recuperator before being recirculated because the temperature of the recirculated exhaust gas is higher the relative proportion of exhaust gas that must be recirculated is lower than for the embodiment of fig2 all other factors being equal in other respects the operation of this system is the same as that of fig2 the manner in which the exhaust gas is recirculated and mixed with the air and fuel can be varied in the practice of the invention fig5.