Method for operating an internal combustion engine by adaption of mixture pilot control

The internal combustion engine exhaust system contains a pre-catalyser and a main exhaust gas catalyser. The control system may act as a mixture control and may have a circuit block (10) with an input (12) from a sensor downstream of the pre-catalyser and an air mass flow input (14). The circuit block contains a filter (16), a gradient block (18) and a settle-check block (20). An integrator block (22) is connected to the air mass flow input. The settle-check block receives an input from a catalyser model block (40) which has inputs (28,30,42) from the engine. The control system also contains a flash adaptation block (26).