is modeled more closely by two first order airflows the flange exhaust temperature t flange1 may be used alone or in combination with a thermocoupled model 92 the thermocouple model 92 is an optional portion of the control system the thermocouple model 92 allows verification of the exhaust gas temperature at the flange by modeling the thermocouple the output of model 92 should correspond directly to an actual thermocouple on the vehicle during testing thermocouple model 92 has an air mass input 94 because the thermocouple model on tau 2 input 93 is dependent on the air mass in a similar manner to that of heat transfer model 78 in addition a feedback loop 96 including memory 98 that stores values into memory and an initial condition block 100 the initial condition block is coupled to an old_avg input to model 92 the output of thermocouple model 96 provides a second flange temperature t flange2 which is the output of the control system 70 when a thermocouple is taken into consideration one model is given by the formula t flange2 t flange1 u03c4 2 ue89e uf74c t flange1 uf74c t where u03c4 2 in general is a function of the exhaust flow rate and thermocouple size is the temperature of the thermocouple junction and the output of the mixing model and t flange2 is the temperature of the exhaust gas at the output of the model referring now to fig3 mixing model 90 is illustrated in further detail mixing model 90 receives the temperature t1 from heat transfer model 78 and temperature t2 from bypass loop 76 a constant block 102 which is.