2.5 or 3 inch cat back?

[PlanZero]

I was going to slap an eBay cat back on my Tsi fwd. Is there any difference between the 2.5 and 3" (which shrinks to 2.5 at the cat), since I'm still using the stock cat and downpipe? I have a full 3" apexi with high flow cat on my awd, and I'm not expecting the same from this, so is it pointless to get a 3" cat back?

 

[GRAVEDIGGER]

If you're still choking it with a factory downpipe and cat I see no reason for the 3". The 2 1/2" should work just fine.

 

[PlanZero]

Yeah that's what I figured. This car is mostly bone stock, and the stock muffler is shot, so I was just gonna get a cheap catback for now. The 2.5" run for under $100, so why not?

 

[fredom dsm]

If you plan on driving the car mostly stock then yes. 2.5 is enough but if you plan to start modding in the future, I would suggest 3" and spend your money once.

 

[Priority DSM]

http://www.dsmtuners.com/threads/1997-gst-what-catback-exhaust-in.493034/

-thread from like 2 days ago

I used the search button because I don't like beating horses to death.

 

[PlanZero]

actually I prefer beating as opposed to other methods; it's more entertaining. Seriously, is the SRS 3" cat back actually a 3" inlet, or does it shrink to 2.5"? It seems most of the 3" do this, which leads me back to my original inquiry as to what difference it makes if it's still attached to a 2.5" cat, such as the stocker. The catback section of my apexi is cut and welded to the hi flow cat

 

[bo0st]

Before getting an expensive exhaust you should just delete the cat if you've already passed emissions.

You'll feel a good difference.

 

[ADarling_GSTX]

If you plan on driving the car mostly stock then yes. 2.5 is enough but if you plan to start modding in the future, I would suggest 3" and spend your money once.

Yea I agree. Until you let it breath through a larger down pipe, there's really no reason to go with 3 inch piping.

 

[Priority DSM]

Yeah. If you are still running your cat then pick any exhaust system you want, the .5 inch difference between the 3 and 2.5 will be the least of your flow issues.

 

[clivelive95]

I was going to tell you that you will continue to mod the car because that is what happens when you own one of these but I saw your reference to the awd car which mean you own more than one. Put the real money into the awd car, keep fwd stockish, and go the cheaper route with 2.5".