Method for determining a delay time of a pre-catalytic converter lambda probe and method for determining the oxygen storage capacity of an oxygen store

A method for determining oxygen storage capacity of an oxygen store associated with a catalytic converter of an arrangement with an internal combustion engine, wherein a pre-catalytic converter lambda probe is arranged upstream of the catalytic converter and a post-catalytic converter lambda probe is arranged downstream of at least one section of the catalytic converter, the method comprising:

• supplying a difference between an output signal of the pre-catalytic converter lambda probe and a desired signal to a controller as an input signal,
• measuring an output signal of the controller, said output signal determining an air-fuel ratio of the exhaust gas to which the pre-catalytic converter lambda probe is exposed during the operation,
• determining a first time when a first output signal of the controller satisfies a first predetermined criterion,
• determining a second time following the first time when a second output signal of the pre-catalytic converter lambda probe satisfies a second predetermined criterion,
• determining a time difference between the second time and the first time, said the time difference defining the delay time,
• removing as much oxygen as possible from the oxygen store and thereafter completely filling the oxygen store with oxygen to a certain level, or filling the oxygen store with as much oxygen as possible and thereafter completely removing oxygen from the oxygen store to a certain level, and
• determining a quantity of introduced or removed oxygen per unit time over time interval, which starts at a third time when the output signal of the pre-catalytic converter lambda probe satisfies a third predetermined criterion, and is terminated at an end time which is computed by adding the delay time to a fourth time when an output signal of the post-catalytic converter lambda probe satisfies a fourth predetermined criterion.