Page 71 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Robert Bosch GmbH. 53

It is also logical to assume that the value of the air mass flow is constant and equal to the one
at time To. By also setting kj I the above mentioned formula is drastically simplified.

is
If fA~ a predefined time interval and

then the formula becomes

If the value of AZ is lower than a predetermined threshold E then the catalytic converter is
considered to have been deteriorated.
The method requires no special test running of the engine and can be carried out at any
stationary running state of the engine.

catalytic converter
slightly deteriorated

catalytic converter
greatly deteriorated

TIME

Fig. 23 (ffom DE41 39560)