US Patent 7946117 Onboard method of determining EGR flow rate

A method of determining and regulating a mass flow rate exhaust gases recirculated into an engine is disclosed. The method may comprise directing the exhaust gases through a venturi and sensing a differential exhaust pressure across the venturi. The method may further include sensing an absolute exhaust pressure at the venturi, and sensing a temperature of the exhaust gases. The method may further include determining the mass flow rate of the exhaust based on the sensed differential fluid pressure, absolute fluid pressure, and temperature.