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Originally Posted by Nick
Where does that info come from?  |
Most of the freer-flowing aspect of "performance" cats comes from less or less dense media to flow through. The only way it could really be as effective and flow better would be if it were bigger than the OEM cat. If you've seen the OEMs vs bullet cats, that isn't even close to true. The other way it could flow better and be as effective would be if it had some better technology (like modern cats vs pellet-type cats). But there is no new/high technology in RT cats and the like that OEMs haven't already been using for years.
On many OBD-II vehicles, aftermarket high-flow cats will set off the check engine light or require O2 simulators, because the cat does a worse job of catalyzing and the post-cat O2 sensor can readily detect it.
Plus, bullet cats on long-tube headers move the cats further down the exhaust stream, so they will take longer to heat up and start working.
But most of us just need "just enough" catalyst to pass state emissions requirements (which are much less strict than new-car emissions requirements), and want as much power as possible while staying right on the edge of passing.