A control system for controlling an internal combustion engine having an exhaust gas recirculation mechanism consisting of an exhaust gas recirculation passage connected between the exhaust passage and the intake passage of the engine, and an exhaust gas recirculation valve provided in the recirculation passage for controlling an exhaust gas amount to be recirculated. An air circulation system includes a passageway having an air inlet and an air outlet connected to the chamber. The first command and the second command are received by the resident external controlling interface which queues the first and second commands. The flat tubes can be constructed of relatively thin material, and can be reinforced with folds of the flat tube material andor of an insert in areas subject to higher pressure and thermal stresses.