Page 267 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

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under test conditions and a catalytic converter working under normal conditions the better the
efficiency of the catalytic converter is.

In the method of WO9404800 (1994) the catalytic converter is divided in a number of volume
elements K, to I(4 (fig. 108). One temperature Sensor is installed in each of the volume
elements indicating representative reaction temperatures in each of the elements. A
modification of chemical and/or physical properties of the exhaust gas mixture takes place in a
way similar to the one of the method of DE4227207 (1994) described above (step 2). The
method of DE4227207 (1994) as presented in fig. 107 is then applied separately for each
volume K, to &. The difference of the max. values of the temperature derivatives between a
catalytic converter operating under test conditions (increased quantity of HC) and a catalytic
converter operating under normal conditions is compared to predetermined values for each of
the volumes K1 to I<4. The results are stored in a storage device and are processed in a later
stage to draw conclusions for the efficiency of the catalytic converter in different operating
conditions.

PDL; control

/
5-41 Volume element I indication
a-4: Temperature sensor

D1-4: Differenciator LtJ Lc-l
storage device storage device

Fig. 108 (from W09404800)