ENGINE CONTROL SYSTEM

To circulate exhaust air by properly switching a device and a bypass passage according to a corrosion rate of each of acid components included in condensate water.SOLUTION: An engine control system (10) includes a bypass passage (33), a selector valve (34) for selecting a first state in which exhaust air is circulated to an EGR cooler (32) and not circulated to the bypass passage, and a second state in which the exhaust air is circulated to the bypass passage without circulated to the EGR cooler, and an ECU (40). The ECU calculates each correction hydrogen ion concentration by multiplying each hydrogen ion concentration calculated from concentration of each acid component included in condensate water of the exhaust air, by a coefficient according to a corrosion rate of each acid component, calculates correction pH of the condensate water on the basis of the total correction hydrogen ion concentration obtained by adding the correction hydrogen ion concentrations, selects the second state by the selector valve when the correction pH is a prescribed pH which causes corrosion of the EGR cooler, and selects the first state by the selector valve when the correction pH is not the prescribed pH.SELECTED DRAWING: Figure 1 【課題】凝縮水に含まれる各酸性成分の腐食速度に応じて、装置とバイパス通路とを適切に切り替えて排気を流通させる。【解決手段】エンジン制御システム（１０）は、バイパス通路（３３）と、排気がＥＧＲクーラ（３２）を流通してバイパス通路を流通しない第１状態と、排気がＥＧＲクーラを流通せずバイパス通路を流通する第２状態とを切り替える切替弁（３４）と、ＥＣＵ（４０）と、を備える。ＥＣＵは、排気の凝縮水に含まれる各酸性成分の濃度から算出した各水素イオン濃度に、各酸性成分の腐食速度に応じた係数を掛けて各補正水素イオン濃度を算出し、各補正水素イオン濃度を足した総補正水素イオン濃度に基づいて、凝縮水の補正ｐＨを算出し、補正ｐＨがＥＧＲクーラを腐食させる所定ｐＨである場合に切替弁により第２状態に切り替え、補正ｐＨが所定ｐＨでない場合に切替弁により第１状態に切り替える。【選択図】 図１