Method and apparatus for measuring and controlling the egr rate in a combustion engine

The present invention provides for a method and apparatus for measuring and controlling the EGR rate in a combustion engine system, comprising an EGR cooler, an EGR valve and a turbine, and determining the EGR mass flow (dm EGR ) from the difference between the total exhaust gas mass flow (dm Tot ) across the engine cylinders, and the turbine mass flow (dm Turb ) across the turbine.