of the richness data recorded by the richness probe 12 and received by the processor 10 the latter will control the injection time in such a way as to maintain an air fuel mixture that has a richness more or less in accordance with the imposed richness setpoint value the control unit for closed loop richness regulation therefore has the role as we have just seen of ensuring that the mixture richness setpoint ri_spt is adhered to there will therefore be measured via the richness probe 12 the richness in the exhaust line 11 ri_mes the richness of the mixture will be corrected as a function of the richness value measured in the exhaust line 11 using the delta between these two information items m_carb is the setpoint mass of fuel to be admitted per cylinder m_air is the mass of air admitted per cylinder defined from a model or from a direct or indirect measurement thus in internal combustion engines the quantity of fuel to be injected or the setpoint richness as required is defined and the other of those data items is deduced thus either m_carb is fixed and ri_spt is deduced or ri_spt is fixed and m_carb is deduced m_carb will be used directly to control the injectors using the characteristics thereof and the operating point a closed loop richness regulator ri_bf can therefore be defined as follows ri bf ri_spt bf where bf bf ri_spt u2212 ri_mes bf being the closed loop factor and bf being a function which fairly progressively reintroduces the discrepancy between the setpoint and the measurement in order to standardize this regulation cl is defined as follows for.