High-Flow Catalytic Converters

[belize1334]

There seem to be two styles of high-flow cats (excluding resonators that are advertised as cats). Is there a general consensus on which is better and why?

Type-1

Type-2

My concerns are 1) performance (i.e. actual emission quality w/o sacrificing too much flow) and 2) size and fitment. The round style seems like it would be easier to tuck up under the car for good ground clearance but most of the cat back systems I see people selling use the oval style which also incorporates a heat shield into the construction so ...

 

I've used both.

I like to be able to be "Compliant" for the local smokies, so a real cat fits the bill. Then take up the slack in diameter of piping.

The "Resonators" work really good when you have an otherwise straight-through 3". quiets it down pretty well.

Real catco cats are cheap nowadays anyways...

 

[belize1334]

I'm leaving resonators for another day. Both of the one's I listed are "real" cats. Is one of them not compliant for some reason?

Magnaflow apparently makes a barrel style spun converter which they say is awesome. They're on sale right now from one of their vendors for ~$65 with free shipping.

clicky

Has anybody run one of these? Opinions?

 

[Dialcaliper]

Metal core is better from a flow and durability standpoint because they tend to have much more open cores. They also tend to be more expensive. ceramic is better from an emissions standpoint (finer mesh, more surface area for the catalyst to operate)

Cores are essentally all similar lengths, so basically it's all about cross sectional area of the core. Ovals tend to be better than rounds simply because you can expand the converter sideways more than you can up and down due to clearance issues, provided you can fit the extra width.

Metal > Ceramic
Big > Little

If you want the best flow that's easily available, I'd recommend the Vibrant model. If you want the absolute best high flowing cat, which is questionably legal in the US, SureFlo in Australia makes very porous 5" dia "ballistic" cat that claims about 700 cfm at 28" water (1 psi drop). Considering that a 3" open test pipe will flow a bit over 1000cfm at the same pressure drop, that's pretty damn good - you're looking at less than a 0.5psi drop compared to the open pipe, provided that you're flowing even close to 1000cfm (about 70 lbs/min, more than many turbos can even put out).

 

[belize1334]

Ok. So the round core metal ones flow more but places like California don't like them. Considering I'm sans cat right now, I think that one of those will be better than what I got while striking a compromise between the killing of exhaust flow vs. baby seals.

 

[Andy_S]

I always had good luck with the oval catco cats. Was easy to make fit, didn't hurt flow (I couldn't tell from the butt dyno at least), and passed emissions when required. I also liked not having the bumper around the muffler getting all full of soot and my car sounded really good. No resonator, just a magnaflow with cat and it wasn't loud at all. And there cheap.

 

[G]

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