| 摘要 |
The diagnostic device takes a signal (S1) from an oxygen probe (10) downstream of a catalyser (4) which receives exhaust from two rows of cylinders (2a,2b). The signals may give a false indication of catalyser efficiency due to phase opposition in the two exhaust channels. A better indicator may be obtained by producing a sliding average of the signal variations which is then passed through a low pass filter. The low pass filter has a time constant which varies inversely with the instantaneous value of the original signal (S1) and the final indicating signal decreases more slowly than the sliding average.
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