Quote:
Originally Posted by hancock1701
I'm trying learn more about the catalytic converters on our cars, and have a few questions.
Why are there 2 on each bank? Does the integrated cat function the same as the downstream cat?
Why is the integrated cat called the precat, even though it's the one monitored by the O2 sensors? Why have two but only monitor one?
Since they don't do the sniff test anymore, the downstream cat shouldn't make a much of a difference in terms of getting tested, right?
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the pre cat is closer to the engine and smaller, so it gets hot really quick on a cold start, lowering starting emissions.
Once the main or three way cat is hot, it has much greater conversion capacity than the pre cat, so it is the only one monitored.
Removing the main cat will lead to problems in two areas: The car will code as the O2 sensors have nothing to go on. With your CARB inspections, the cats have to physically be there, they actually look.