I'm debating on whether or not to replace the stock cat. on my car. I will be replacing the downpipe and cat. back. My goals for the car are to make it as close to stock sounding as possible and more importantly will pass New Jersey emissions.

My questions are:

What types of gains did those of you with a bigger downpipe, cat back, and the stock cat see?

Is there anybody from NJ with a high flow cat. that has passed emissions during inspection?

Thanks for the help.

PS. This is for an EVO and not my Talon, not that it really matters.

 

No point whatsoever in replacing the dp and catback without changing the stock catalytic. It's the biggest restriction in the exhaust system...

 

The stock exhaust system uses 2.5" pipes I believe, so if you wanted you could just swap out the cat to a 2.5" straight pipe (and back again for emissions), right?

Is there a really big difference switching to 3" pipes? I would presume the entire lot, starting from header down to muffler would need to be swapped to the 3" pipe size to do it correctly?

 

you can just swap it back when its time to smog your car.

 

The BR330, and 350 still retain the stock cat, and they seem to respond very well with the mods....

 

Thanks for the quick replies everyone.

Swapping out a test pipe for a cat during inspection is not an option, although easy enough to do. I guess I should share my whole story as to why it's not an option.

I work for a Mitsubishi dealership and am considering trying to get involved in selling and installing aftermarket performance parts. The 4g63 has been a passion of mine since I first rode in a 1g Eclipse and VR4 Galant back in the early 90's and I want to take it to the next step.

My goal is to put together a small package that performs well, is user friendly(low noise level and streetable), and can pass emissions without getting your hands dirty swapping parts.

At this point I think my best bet is going to be purchasing a 2.5 inch high flow cat. with the downpipe and cat back and smog test it.

Thanks for the help.

 

If you can, avoid changes in diameter sizes as if they were the devil. Going from 3->2.5->3-inch distrupts the exhaust flow and reduces power output. Seen it time and time again. Better off using a 3" high flow cat as others have suggested.

Shiv

 

The stock evo cat is the highest flowing cat from any manufacturer. the inside volume is huge for a 2.5" cat and has very thin substrate. Unless jumping up to full 3" from the downpipe and cat back, the stock cat is not really that bad.

 

I have seen this too. Their partnership with Medina Mitsu has also inspired me to start this project.

 

Does the stock cat have a 2.5 inch diameter?

If so, I would have no problems going with a 2.5 DP, the stock cat, and a 2.5 or 3.0 inch cat back.

 

I believe the entire stock exhaust system is 2.25" (according to evomoto.com)

 

You'd really want to stick with either 2.5 all way around, or 3" all the way around and not mix them up.

 

Does any one make a 2.75inch test pipe or high flow cat

 

Test Pipe alone makes 15whp

 

I believe federal law states you may not replace the cat on a new vehicle for 50k miles, I may be wrong, but I thought i read this somewhere. Maybe this is why buschur retains stock cat?