Page 167 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Hitachi Ltd. 149

The conversion efficiency ('1; is calculated by the following equation for compensating an
effect of an output ratio between a high level output period and a low level output period of
the upstream airhe1 sensor

When the calculated converter efficiency in function of the correlation function falls out of a
predetermined region, then the catalytic converter is considered as deteriorated.

lean

b)

coeff.
0.95 I
I
lean I c)
mean t I time
i --------
I
airffuel 14.7 --==
ratio I I I
ricll I I
I
t
1
Voltage

sensor

converter 1
converter

Fig. 69 (from EP0478 133)