Page 131 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey
P. 131
Toyota Motor Co. Ltd 113
Engines with multiple cylinder groups
The following three methods proposed by Toyota refer 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). An oxygen sensor is installed
upstream of each auxiliary catalytic converter (1 a, 1 b, etc.) and an oxygen sensor (2) is installed
downstream of the main catalytic converter. The layout of the engine as well as the electronic
module used for monitoring the efficiency of the main catalytic converter for all three methods
is shown in fig. 56. For simplicity, only two cylinder groups will be considered named as left
and right bank.
The auxiliary converters are three-way catalytic converters and have a small volume in order to
be activated rapidly after the engine is started. The main converter is also a three-way catalytic
converter.
Secondary air is injected in both exhaust branches in order to reduce the emission of HC and
CO during deceleration or idling of the engine
Fig. 56 (from 1135377484)
