Method of determining the oxygen storage capacity of catalysts in multiple exhaust gas systems and apparatus for carry out the method

Method for determination of the oxygen storage capacity of catalysts (22, 24) in a multi-channel exhaust system with at least two exhaust pipes (14, 16) comprises applying different amplitudes and frequencies to each pipe to produce an specific average lambda value. A first oxygen sensor (28) is positioned downstream from the catalyst in one pipe while a second oxygen sensor (30) is positioned downstream from the point where the pipes unite. These measure the change in lambda value, from which the oxygen storage capacity of each catalyst is calculated. An independent claim is included for apparatus for carrying out the method.