Patent ID: 8267069

Claim:
A method of controlling an EGR valve of an exhaust gas system for an engine, having an exhaust manifold and an intake manifold, an EGR flow path between the exhaust manifold and the intake manifold, the EGR flow path having an EGR exhaust gas cooler cooled by engine coolant and the EGR control valve controlled by an engine electronic control unit, the EGR control valve in series with and downstream of the EGR gas cooler comprising the steps of: establishing a low temperature setpoint; providing an EGR temperature sensor downstream of the cooler; monitoring sensed temperature of the exhaust gas from the EGR temperature sensor; monitoring engine coolant temperature; monitoring exhaust gas flow rate through the EGR cooler; estimating an upstream exhaust gas temperature upstream of the EGR cooler using the sensed temperature from the EGR temperature sensor, heat transfer characteristics of the EGR cooler, the engine coolant temperature, and the exhaust gas flow rate through the EGR cooler; and if the upstream exhaust gas temperature is below the low temperature setpoint at least partially closing the EGR control valve.