Quote:
Originally Posted by perryair
so the secondary cat is effective enough to bring emissions down to legal limits when warm? 👍🏻
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Not without modification. The front cat is the primary and the O2 sensors are positioned to manage it, not the secondary. The secondary cat is likely a two-way catalytic converter, as well, so it would need to be replaced with a three-way to see the same benefit.
But as others have stated, the real problem is the warm-up period. Even if you could move the O2 sensors back and replace the secondary with a three-way, it would still take significantly longer to warm up.