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Originally Posted by K-Dubb
I didnt know the stock were high flows. Do you know of any documentation to support that? Just curious.
Thanks.
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The question is, are the aftermarkets you are looking at high flows? High flow Aftermarkets are very expensive. The stock cats use a 400 cpi ceramic honeycomb. Most aftermarket converters regardless of brand name us the exact same cell density and also has the same cross section. If you replace a 400 cpi with another 400 cpi, you gain no flow unless the old ones were plugged.
Now if you replace the stock cats with 300 cpi ceramics, now you are talking. The real world gains are still minimal, but at least the potential is there, and when combined with headers, a good catback, and a tuner and intake, they can help you get the most out of them. They are also great with forced induction. You can also get 200 cpi metallic catalysts. Unfortunately, while the metallic has a freer flowing substrate, the metal ones are only available is small round bodies, which struggle to keep up with demand on a truck. The 300 cpi ceramic has a greater cross section and is also more efficient.
Real high flow cats are expensive because the lower density means less surface area. The only way they can compensate is to increase the precious metal content (platinum, palladium, rhodium), which causes the price to skyrocket. As with anything there are always tradeoffs, in the case of metal cats, the tradeoff is cost and recyclability.
