What kind of inlet/outlet should I get for my cat? Isn't the stock diameter 1.75"-2"? I'm going with an aftermarket cat, and the HKS sport exhaust.

 

Why bother with HKS? It's only the rear section as far as I know. Just get motoria and 2.25" catco cat.

 

I decided to go with HKS because I found one for really cheap, and from what I've heard it sounds great, not buzzy at all and has a very deep tone. Not going all out NA either.

Would I even be able to find a high flow cat that's less than 2.25" in diameter? Exhaust shops should be able to weld it on either way.

 

Check out ebay for 2" cats. They should have some.

 

Why not just go with a 2.25" cat?
It's going to be a restriction anyway, so why not try to minimize that as much as possible?

An exhaust shop should be able to fit a 2.25" to the stock piping.
I just did some exhaust work to my car this weekend and I was able to slip a 2.25" piece of tubing right over the stock stuff, so maybe it's 2"?

I'll try to get pics to better explain, but my advice would be to go with a bigger cat, especially if the HKS is 2.25".

But, if you still want to go 2" this place sells them on eBay:
http://stores.ebay.com/Performance-Curve_M...1QQftidZ2QQtZkm

They've got even cheaper ones too if you surf their store.

 

The stock diameter is 2.25. Why do you want to go smaller?

 

a) I think he was asking what the stock size was.

b) are you sure it's 2.25"? Is it different (smaller) for an Elantra?

 

I'm pretty sure it's 2.25. When I put a custom exhaust on a long time ago, I measured the diameter and it came out to be 2.25 (needless to say I got rid of it and bought a KRD). The pipe diameter should be the same between the Elantra and RD.

 

I'm only asking because I just made my own axle-back exhaust out of a WRX axle back and I didn't want to waste a flange, so I welded a 2.25 ID pipe to the flange and slipped it over the stock piping. (I'm going to do a full 2.25" exhaust and this was "Step 1")

So maybe the stock exhaust is 2.25 OD?

I dunno, just asking... I can get proper measurements tonight after I pick the old muffler out of the trash.

 

Wow, you used a WRX axle back? Pretty cool idea. Could you please show pics when you're done?