So I'm getting my pieces ordered to do a full exhaust on Midnight 2001 3.8L 5spd with a K&N CAI and need some help with the cat. I ordered a set of OBX SS Headers, and a Magnaflow 12277 SS muffler. I bought just the muffler b/c it was cheap compared to the cat-back and I heard it was better to do a 3" pipe from cat to muffler rather then 2.5" supplied with cat-back that makes it sound raspy. I found these cats on eBay and was wondering if these are the right ones or do I need 3" inlet/outlet. If these are good do you know the difference between 94006 & 94106? Any advice is always appreciated.
High Flow Cat Magnaflow 94006
http://item.mobileweb.ebay.com/viewi...id=84295490621
High Flow Cat Magnaflow 94106
http://item.mobileweb.ebay.com/viewi...id=84295490621

 

if your going through all this to get better flow why would you use a cat that is 2.5 on a system that is 3 in. what is the outlet size from the y pipe?

 

Are you custom making the pipe from the Cat to the muffler? Since you are custom building stuff all you need is the correct inlet and outlet we can not really tell you what is correct on a cusom exhaust. See if this helps.

From your OBX Y-pipe you will need a pipe to the cat from the Y-pipe to the Cat ( Universal high flow cats tend to be shorter then stock). You will need your Cat then you need the Pipe from the cat to the intermediant pipe. This S shaped pipe does not come with the "CAT back" system and it is the biggest restriction in a car with headers and a Cat back system. You could make a single pipe that runs from the cat to the muffler but it will need a lot of bends in it.

Also I think your going to find you Bolts that come with your OBX headers are too short. I think the bolts I used ended up being 4-1/2" long that way I could use the springs as they are designed to be used. Since you have an 01 you may need to block off a O2 sensor port in the Y-pipe, since you will need to make a Y-pipe to Cat pipe you could cut he O2 sensor hole off and just make the pipe a little longer. The OBX Y-pipe is designed to fit the factory CAT.

Good luck.

 

Good point Craby. I will wait for the headers to come in and measure cause Im not sure the end of the Y-pipe I hope it's 3". Then I'll order the cat.

Gorn thanks for the heads up on the bolts and all the helpful info. We'll see how it goes.

Happy holidays!