Method for controlling a combustion engine according to an estimation of the mass fraction of burnt gases in the intake manifold

The method involves performing a measurement relative to flow rate of gas, fresh air or burnt gas, in upstream of a mixing space in which the air and the burnt gas are mixed. Burnt gas mass fraction (BGRbp) present in the space is estimated from the measurement and a model of mixing dynamics in the space. Transport delay from the space to an intake manifold is estimated. Burnt gas mass fraction in the manifold is estimated in real time from the estimation of the burnt gas mass fraction in the space and the delay. Combustion from the burnt gas mass fraction in the manifold is controlled. An independent claim is also included for a combustion engine.