3 inch exaust and DP..

[varGST]

i purchased a 3 inch cat back exaust. i'm thinking about now purchasing a down pipe. yet my exaust changes to connect to the cat, its no longer 3 inches. if i were to get a 3 inch downpipe, does the downpipe change as well to fit the exaust? or do i need to purchase or modify my exaust to fit the downpipe? because isnt the cat eliminated?

hmmm ?

 

[SikRacing97GST]

what kind of cat back do you have??

 

[2gGSX]

From what I understood from your post.. you bought a "3 inch catback" that necks down to connect to the stock cat, and are wondering if your downpipe needs to neck down as well to fit the cat but you're getting getting mixed up between normal downpipes and cat eliminating downpipes.

Depending on what downpipe, it may or may not eliminate the cat. If it doesn't and you want to keep your stock cat (for some reason) you'll have to have that neck down to fit as well or get an adapter. If it does and it's a 3" downpipe, you're screwed since it won't fit to your catback due to it getting smaller, and you'll either have to get a new one or cut off the neck down part and do some welding.

At least that's what I think you're asking..

 

[David15151]

either get a downpipe that eliminates the cat and go to a muffler shop to have them cut off the reducer on the cat-back and weld up some 3" pipe to run to the downpipe OR get a 3" downpipe with 3" high-flo cat and do the same as above to connect it. Any other way of doing it would be throwing away our money because having a stock cat or having a pipe reduce down will create a large restriction in your exhaust flow and lesson HP gains quite noticably.