Page 62 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey
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44 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters
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Fig. 15 (from US4007589)
In DE4009901 (1991) the aidfuel ratio of the engine starts oscillating at certain operating
values of load and rotational speed. The signal from each probe then starts fluctuating around a
mean value q.2 within allowable limits If both signals exceed their limits for longer than a
preset period of time (fig. 16) then an alarm signal is produced indicating a failure of the
catalytic converter.
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downstream probe
Fig. 16 (from DE4009901)
In DE4024210 (1992) the aidfuel ratio starts oscillating at predetermined operating conditions
around a mean value from rich to lean and vice versa. The predetermined conditions are
defined as a stationary load-rotational speed point, where load and speed changes remain
between certain limits for a predetermined time interval. The measured ratio of the two probe
signals is then formed:
