Monitoring Catalyst Efficiency

Monitoring the efficiency of the Three Way Catalytic Converter (TWC)
In this process the oxygen storage capacity of the TWC is determined by comparing the oxygen sensor amplitudes ahead and after the TWC. If the oxygen storage capacity is diminished through aging of the TWC, the oxygen sensors after the TWC also show voltage amplitudes. The amplitude of the oxygen sensor ahead of the TWC is used as the target value and is therefore determined through the same signal path.

The quotient of the rear and front amplitude, the amplitude ratio, is used as the measuring value. The appearance of amplitudes after the TWC is dependent on the momentary load of the storage capacity of the TWC. This load can vary from load to rpm, which is why a load and rpm-dependent evaluation (tl/n) is done.

TWC is OK:

A: Sensor amplitude ahead of TWC
B: Sensor amplitude after TWC

TWC is NOT OK:

A: Sensor amplitude ahead of TWC
B: Sensor amplitude after TWC
X: Delay due to gas running time

NOTE: The comparison of both sensor voltages is the measurement for the efficiency of the Three Way Catalytic Converter