Page 224 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

206 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters

Engines with multiple cylinder groups

The method of JP5098946 (1993) proposed by Nissan refers to the case of an engine with
multiple cylinder groups, where there is an auxiliary catalytic converter in each individual
exhaust passage of each cylinder group. A main three-way catalytic converter is also installed
in the common exhaust pipe section of all cylinder groups (fig. 56). The distribution of exhaust
sensors is similar to the one of fig. 56.

The engine adtiel ratio is feedback-controlled and the deterioration assessment of the
auxiliary (secondary) catalytic converters and the main catalytic converter takes place by
comparing the output signals of the oxygen sensors placed upstream of the auxiliary converters
and the oxygen sensor placed downstream of the main converter.