I've read a lot about aftermarket hi-flow cats not holding up to the test of the rotary engine so I was pondering the idea of modifying the stock cat to flow better.

I would have the stock cat pipes cut off at the cat body where it's somewhat bigger and weld 3-inch pipes with flanges custom made or from a cheap midpipe; any muffler shop could do it. And no, I'm not gutting it.

I figure the stock cat's core flows more than enough but is restricted by the smallish stock pipe diameter. This would be a fun and maybe cost effective way to have a durable higher flowing cat. I won't save any weight though... What do you guys think??? Have anybody done this before?

 

Sounds like a good idea to me. Might be expensive.

I modded my stock cat by rewelding the flanges on the outside, and grinding down the inside weld for a full 2 1/2 inch opening. This resulted in about about a 40% increase in the opening on each flange. I could feel a difference in performance after doing this. Your mod would double the size of the openings.

 

I've got an extra low-mileage cat that I'll be doing a few things to, including grinding the inside pipe down a bit to improve flow. Hey, it can't hurt .

But, that is a good idea to make it totally 3" in and out. Some muffler shops may not want to touch the cat, though - they're really not supposed to do much with cats legally. Just depends on the shop.

I'd get some good 3" flanges like the ones Racing Beat sells and have the shop fab up the piping. That should result in a quality setup.

Dale

 

the cross sectional area is much larger then the high flow cats. it works well. but is that main cat system heavy!

 

I'm not sure about doing it yet... I'll let you know if I do