How much power do high-flow cats free up?

Out of curiosity, how much power do you guys think I could pick up with a high-flow (2.5") catted h-pipe? My mods are in my sig, obviously the '90 not the '66...

I've had offroad h-pipes on my past cars, but I really don't want to deal with swapping the stock h-pipe back in for emissions any more. I figured the stock h-pipe might be holding me back with the supercharger.

Also, is there much of a sound difference going from stock h-pipe to high flow catted h-pipe? I know there's quite a difference when you remove the cats all together.

Thanks.

HISSIN50 said:

Jeff, I also gotta believe that the stock cats are a bottleneck with your forced induction. I'd consider the same thing you are. Or for off road purposes only , you could get an O/R pipe and a couple of aftermarket 3 way cats. Make the OR modular where it can have the cats installed or a straight pipe (use flanges to achieve this).

One other thing - when I lived in King County, things were pretty relaxed with emissions but I would ensure that you won't flunk with an aftermarket catted pipe (because you are technically going from four cat housings down to two).

Good luck bud.

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A couple of years ago they started using the dynos again here in King County. Before that, a good running 5.0 with no cats would squeak through emissions. Now that they're running the dynos again, I couldn't get my dads car through.

They still don't do under-car or under-hood checks though. I heard that if you fail they can look under the hood or car, but I've never had them do that. I guess we've got it worse than some places, and better than others.

I'll have to look into the cost of aftermarket cats, and see about building my own catted pipe out of an offroad. Those damn catted h-pipes aren't cheap.

Thanks for the input.