Quote:
Originally Posted by rmay635703
Older cars (pre 2000) had 2 way CATS or modified 3 way
which aren’t affected by that issue, they also more importantly didn’t need to meet the more stringent NOx limits of later years so some NOx could pass a full trap without issue.
The Insight and newer had a Nox trap and would cycle lean to rich to make sure the cat stayed lit and the NOx levels didn’t increase after the NOx trap filled.
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So, perhaps as the mixture goes lean, the CAT cools, and its efficiency decreases. That would mean a DIY lean burn system would inevitably cough out more NOx, which was a major culprit in SoCal smog back in the bad old days of fog banks in the desert.
