Abstract: An exhaust gas recirculation system for a compression ignition engine is provided wherein the exhaust gas recirculation is shut off depending upon the sensed or calculated humidity in the intake manifold relative to the dew point of the exhaust/intake air mixture. The humidity of the exhaust/intake air mixture may be measured in the intake manifold, charge air mixer or the ambient humidity may be sensed. If humidity is measured in the air charge mixer or in the ambient air, other factors such as engine speed and load, intake manifold pressure, EGR flow and air/fuel ratio may be used to calculate the humidity in the intake manifold. When the temperature of the mixture in the intake manifold is less than the dew point of the mixture, the engine control strategy may be shut off the EGR to prevent condensation in the exhaust gas recirculation system or engine.

Abstract: An exhaust gas recirculation system for a compression ignition engine is provided wherein the exhaust gas recirculation is shut off depending upon the sensed or calculated humidity in the intake manifold relative to the dew point of the exhaust/intake air mixture. The humidity of the exhaust/intake air mixture may be measured in the intake manifold, charge air mixer or the ambient humidity may be sensed. If humidity is measured in the air charge mixer or in the ambient air, other factors such as engine speed and load, intake manifold pressure, EGR flow and air/fuel ratio may be used to calculate the humidity in the intake manifold. When the temperature of the mixture in the intake manifold is less than the dew point of the mixture, the engine control strategy may be shut off the EGR to prevent condensation in the exhaust gas recirculation system or engine.