Best high flow cat?

[jledford]

I'm looking into building a custom exhaust over the winter for my E30. This would be mainly to save weight but if I could free up the exhaust and gain some power that would be nice as well. The rules in STX say that a cat-con has to be run. I'm looking at doing long tube headers into a y-pipe and then a single pipe (instead of duals) to the back of the car. I'd probably go either 2.25" or 2.5" piping through a high flow cat and then into a magnaflow muffler. So my questions are:

Is there a preferred high flow cat?

Ceramic vs metal core?

Best for the cell count to be the lowest for maximum flow?

Are the magnaflow ones from jegs or summit just as good as others?

Edit: So I just found this place: http://www.mil-spec.org/2.5-100-Cell-Weld-In-Cat.html Seems to get good reviews, I assume this counts as a legal cat in SCCA?

I'm researching as much as possible but any advice or personal experience would be appreciated!

[nicktcr]

I thought the solo classes that required a cat required that it be the factory cat? Perhaps I misread that though. I have no advice on high flow cats, as the highest flow I could get was a 3 inch pipe. Flows pretty well

[jledford]

I'll have to double check the rules. I know stock classes require factory cats but I thought with STX I could get an aftermarket as long as it's located within 6" of the original cat location.

Found it, section 14.10:

D. Exhaust manifolds and headers (including downpipes) may be replaced
with alternate units. Mounting brackets/hardware which serve
no other purpose are considered part of the exhaust components.
E. Catalytic Converters - Any high flow catalytic converter(s) are allowed,
but must attach within six inches of the original unit. Multiple
catalytic converters may be replaced by a single unit. The inlet of the
single replacement converter may be located no further downstream
than 6” along the piping flow path from the original exit of the final
OE converter.

[nicktcr]

Yeah that makes sense. I was thinking of the stock class I suppose. I'll ask around some of my friends and see if any of them have an recommendations on high-flow stuff.

[SamC]

Move to street prepared and get test pipes. That's what i did.

[nicktcr]

Move to street prepared and get test pipes. That's what i did.

Or this

Or XP and cut the whole exhaust off

[jledford]

Move to street prepared and get test pipes. That's what i did.

I've thought about that but then I'd be tempted to do all the other DSP legal mods. I'm going to try to stick with STX for another year and get some things sorted with the suspension. After that I'll look into street prepared, installing fender flares and putting some 275 slicks on

[TouringBubble]

From everything I've seen, MilSpec cats are about the best you can find. But, I think they only make a 3" version.

[jledford]

Check my link in the first post, they have a 2.5" 100 cell

[TouringBubble]

Awesome. Yeah, I've seen tests of the MilSpec cats and they only have minimal restriction. Only a small difference in flow from a test pipe.