A method for determining the mass flow rate (D 1) of fresh air entering the intake manifold of an internal combustion engine equipped with an exhaust gas recirculation circuit of the engine in said intake manifold, which recirculation circuit is equipped with a recycled gas regulating valve, which intake manifold incorporates a water-cooled air exchanger and upstream of which intake manifold there is a valve for regulating the flow rate of the gases entering said intake manifold, characterised in that it comprises at least the steps of: - determining the mass flow rate (D 2) of the recycled gases entering the intake manifold, and - determining the mass flow rate (D 3) of the recycled gases and fresh air entering the intake manifold comprising the steps of: • determining the temperature (T A) of the gases upstream of the valve for regulating the gases entering the intake manifold, • determining the pressure (P A) of the gases upstream the valve for regulating the gases entering the intake manifold, • determining the pressure (P B) of the gases downstream of the valve for regulating the flow rate of the gases entering the intake manifold, • applying the following formula: D 3 = Qth = S. Pa rTa 2 ⁢ γ γ − 1 Pb Pa 2 γ − Pb Pa γ + 1 γ Where S is the gas passage section at the valve for regulating the flow rate of the gases entering the intake manifold, T a is the temperature of the gases upstream of the valve for regulating the gases entering the intake manifold P a is the pressure of the gases upstream of the valve for regulating the gases entering the intake manifold, P b is the pressure of the gases downstream of the valve for regulating the gases entering the intake manifold, r is the gas constant, γ is the gas gamma, and - determining the mass flow rate of air (Di) entering the intake manifold by difference between the mass flow rate of gas (D 3) entering the intake manifold determined in the previous step and the mass flow rate of the recycled gas (D 2) entering the intake manifold determined during the first step. - determining the mass flow rate (D 2) of the recycled gases entering the intake manifold, and - determining the mass flow rate (D 3) of the recycled gases and fresh air entering the intake manifold comprising the steps of: • determining the temperature (T A) of the gases upstream of the valve for regulating the gases entering the intake manifold, • determining the pressure (P A) of the gases upstream the valve for regulating the gases entering the intake manifold, • determining the pressure (P B) of the gases downstream of the valve for regulating the flow rate of the gases entering the intake manifold, • applying the following formula: D 3 = Qth = S. Pa rTa 2 ⁢ γ γ − 1 Pb Pa 2 γ − Pb Pa γ + 1 γ Where S is the gas passage section at the valve for regulating the flow rate of the gases entering the intake manifold, T a is the temperature of the gases upstream of the valve for regulating the gases entering the intake manifold P a is the pressure of the gases upstream of the valve for regulating the gases entering the intake manifold, P b is the pressure of the gases downstream of the valve for regulating the gases entering the intake manifold, r is the gas constant, γ is the gas gamma, and • determining the temperature (T A) of the gases upstream of the valve for regulating the gases entering the intake manifold, • determining the pressure (P A) of the gases upstream the valve for regulating the gases entering the intake manifold, • determining the pressure (P B) of the gases downstream of the valve for regulating the flow rate of the gases entering the intake manifold, • applying the following formula: D 3 = Qth = S. Pa rTa 2 ⁢ γ γ − 1 Pb Pa 2 γ − Pb Pa γ + 1 γ Where S is the gas passage section at the valve for regulating the flow rate of the gases entering the intake manifold, T a is the temperature of the gases upstream of the valve for regulating the gases entering the intake manifold P a is the pressure of the gases upstream of the valve for regulating the gases entering the intake manifold, P b is the pressure of the gases downstream of the valve for regulating the gases entering the intake manifold, r is the gas constant, γ is the gas gamma, and Where S is the gas passage section at the valve for regulating the flow rate of the gases entering the intake manifold, T a is the temperature of the gases upstream of the valve for regulating the gases entering the intake manifold P a is the pressure of the gases upstream of the valve for regulating the gases entering the intake manifold, P b is the pressure of the gases downstream of the valve for regulating the gases entering the intake manifold, r is the gas constant, γ is the gas gamma, and - determining the mass flow rate of air (Di) entering the intake manifold by difference between the mass flow rate of gas (D 3) entering the intake manifold determined in the previous step and the mass flow rate of the recycled gas (D 2) entering the intake manifold determined during the first step.