Estimation method for determining the oxygen storage capacity of a catalytic converter

An estimation method for determining the oxygen storage capacity of a first catalytic converter (6), which is arranged upstream of a second catalytic converter (7) along an exhaust duct (4) of an internal combustion engine (1) provided with at least one cylinder (2);

• the estimation method comprises the steps of:
• carrying out an initial combustion phase, in which the combustion in the cylinder (2) takes place with a lean air-fuel mixture, namely with too little fuel and excess oxygen with respect to a stoichiometric ratio;
• carrying out an intermediate combustion phase immediately following the initial combustion phase and in which the combustion in the cylinder (2) takes place with a rich air-fuel mixture, namely with excess fuel and too little oxygen with respect to the stoichiometric ratio, at least until a first oxygen probe (S2) arranged downstream of the first catalytic converter (6) and upstream of the second catalytic converter (7) signals a rich air-fuel mixture;
• carrying out a final combustion phase immediately following the intermediate combustion phase and in which the combustion in the cylinder (2) takes place with a lean air-fuel mixture, namely with too little fuel and excess oxygen with respect to a stoichiometric ratio, after the first oxygen probe (S2) signals a rich air-fuel mixture and at least until the first oxygen probe (S2) signals a lean air-fuel mixture;
• determining a flow rate (mexhaust) of the exhaust gases flowing along the exhaust duct (4) at least during the final combustion phase;
• and
• calculating the oxygen storage capacity of the first catalytic converter (6) calculating, as a function of the exhaust gas flow rate (mexhaust), the amount of oxygen entering the first catalytic converter (6) from a first instant (t6), in which the final combustion phase begins, to a second instant (t7), in which the first oxygen probe (S2) signals a switch from a lean air-fuel mixture to a rich air-fuel mixture;
• wherein the initial combustion phase is prolonged until a second oxygen probe (S3) arranged downstream of the second catalytic converter (7) signals a switch to a lean air-fuel mixture.