searched, browsed and came up dry! if this a re-post I am sorry.

I have the megan racing header, s-spipe, and drift spec cat back.
the noise is getting to me and the little extra power just isn't worth the head ache. so I would like to put in a high flow cat (shut it up and for emissions reasons). I want to place the cat in front of the secondary o2 sensor so that I can get rid of my anti-fouler. I wanted to place it in the manifold like the V1 header was origanly but that gives me 6" to cut and weld in a new cat. problem is I can only find one 11" or larger. and the only other place is the s-pipe but that has to many bends to try and modify.

so I was wondering if someone could either give examples of what they did to fix this problem or if they could tell me where to find a smaller high flow cat.

thanks for the help!

 

Don't know whether you're bothered by high noise or rasp - you get plenty of both with an aftermarket header + exhaust. To quiet rasp you need a bigger resonator. To knock down overall noise - and the cat will only help so much - you have to get a bigger muffler.

To rid the anti-fouler, put your hi-flow cat on your midpipe, then weld in a bung behind it for your O2 sensor. Close up the bung on the S-pipe, and extend the O2 sensor wires to reach the new bung. Search some more, I believe someone on this forum did this.

Also, I believe some aftermarket cats are available with a bung already welded on.

 

If your going to weld a cat on the HEADER then just put the stock one back...if you insist look in to magnaflows new SPUN cats they are tiny and highflow.

I did the O2 extension to the mid pipe, but unless you use a CALI compliant cat you will have to always run 91 oct gas.
with just a reg highflow cat when you use 87 the cat's efficiency drops pretty fast and you will get a code for "cat efficiency diminished" you figure it would be backwards with the octane but for what ever reason its not.

your at the point i am too, were the gains from the header are out weighted by the rasp and sound, you have to choose what you want, if you choose the gains from the header then forget the cat and get two 18"(body) 22" length perforated core resonators welded on to a custom mid pipe of either 2.5 or 2.25. and deal with the fact that you will always have a tid bit of rasp on the real high rpm's and that your exhaust will always be a little rich and backfire slightly.
if not then put the stock manifold back and just be happy with a cool sounding muffler.

I drive 80% on the highway 40 miles daily and this is were the Alphas gain can be truly apreciated so guess what i choose...

 

don't have the stock manifold.

and yes I bought the aftermarket one for performance but just can't take it anymore. I want quite deep sound thats emissions legal without destroying the look of the header under the hood, becuase I don't have any real performance mods so might as well look good cause thats I can afford.

 

OK I had pretty much the same issue when i had my Altima. I added a cat between the mid pipe and the header. I ordered a cat from performancepeddler.com and some flanges and just extended the wires for the O2 sensor. The cat already had an O2 bung in it so you're good there. I never had a CEL come on either. Here's a link to the one I bought.

http://www.performancepeddler.com/de...CT_ID=MAG94136

If I were you I would put the cat after the S-pipe and extend the wires on the O2 sensor. It will solve you're problem for the most part.

 

thanks for the help.

I ordered the obx 14" high flow because its the same material (304 stainless) and it has the polished finish and looks like a resonator so will still appear as though it was part of the megan setup from the factory.

I will hopefully have the cat installed this weekend so I will take pics and post up.

again thanks for the help.

 

I hate to tell you this but that isn't a cat. It's just a straight through resonator. Might help with the sound but not the CEL.