high flow cat size...

[nine9rs]

i have a 420 and am planning to turbo. before i do so im going to get new exhaust, prefferable 70 or 80mm. my question is that if i get a high flow cat, most are 2.5'' so how would that effect larger diameter exhaust? would it bolt up correctly?

 

[L2RTSiAWD]

70mm is about 2.5
80mm is about 3inch


Moved to NT performance.

 

[guedo512]

get the cat when you go turbo. why get a 70mm for your n/t, you will just want to change it to a 80mm when you go turbo.

 

[qwall]

when do you plan on going turbo? if you get 3in right now it'll be too big for n/t and if you get 2.5 you might regret it once you get turbo.

 

[nine9rs]

Originally posted by qwall
when do you plan on going turbo? if you get 3in right now it'll be too big for n/t and if you get 2.5 you might regret it once you get turbo.

i have no date set for turboing its just a step by step process.
by the way 70mm is about 2.75 inches, and as of right now i can care less if i loose performance in my n/t because my goal is turbo. my question was... would a high flow cat bolt right up. since most are 2.5'' will i have to get a high flow cat that is in accordance to my exhaust diameter

 

[qwall]

you'll need to get a flange/coupling but yea it'll be fine but it's best when everything is the same size thru the end.

 

[nine9rs]

do they make hi-flow cats for our cars that are larger than 2.5?