Catback, Downpipe (I'm a little confused)

[Who]

Ok I am a little confused about the way a new catback would mate up to the existing OEM Catylitc converter. For example... Lets say I buy a Tanabe 3" catback. How does the Tanabee 3" connect to the oem 2.5" Cat converter?

I have a similar question concerning downpipes. Pasted below is the description for the the HKS downpipe sold at titanmotorsports.
"This 3" diameter HKS downpipe replaces the pre-cat" "This DP can be used with your factory exhaust, aftermarket cat-back exhaust or with our test-pipe for total CAT elimination."
How would \ could a 3" DP hook up to the Oem Cat or even to the Oem turbo elbow?
Gracias!

 

[BorHor]

The way the flanges they will hook up together. the down pipe you are talking about gets rid of the cat that is in the middle of the down pipe. all in all everyhting will hook up together, even if the diamiters are all different.

 

[suprahabsfan]

It will work with stock cat, but i would HIGHLY reccomend a 3" downpipe and turbo elbow along with your exhaust. The factory elbow and downpipe are ridiculously restrictive. You wont notice MUCH gain with just a cat back. If you upgrade the whole exhaust from turbo back, to 3", the results are nothing short of spectacular, especially when upping the boost in conjuction.

 

[OneJArpus]

sounds stupid but i used a 4'' cat back on a stock cat i know tisk tisk.

 

[akito]

May be the diameter of the car is 2.5 but the flange for the cat is adaptable with the 3. inch exhaust flange

 

[Rmk3turbo]

Also i would make sure that the tanabe down pipe is full 3" and doesn't have a 2.5 inch inlet.

 

[Who]

Sounds like from your replies that the catbacks and downpipes use the same size flanges when it comes to the connection at the cat converter. Allowing you to keep your oem cat convertor.

 

[OneJArpus]

my flandge was a 3'' on the 4'' cat. it was reduced at the flange for either a 3'' test pipe or stock cat with no problems

 

[becauseican]

We at BIC use flanges that have the same bolt spacing as the stock flanges, but with a 3" center hole instead of the 2.25" of the stock flanges. This way you can use any of the stock components with aftermarket or BIC parts.

Randy

 

[Who]

Thank you all !!! That cleared my confusion up nicely.:thumbup: