I'm contemplating custom fabbing a 3 inch exhaust for my stock 2wd 97 A4 1.8T, but I'm not sure what kind of problems I'm going to run into. Am I going to run into boost creep problems or pull any engine codes?

 

3in piping rite
i think 2.75 would be the best i heard caasue u still get some back pressure

 

There's that much difference between 2.75 and 3"? Hmmm....

 

yea there is a .25" difference. Waht kin dof question is that, i hear dthat 3 is the biggest u could go. i would say for with 2.5 but i dont know about back pressure that much. 2.75 would be a good comprismise.(sp)

 

I meant difference in back pressure...
I'm sure a 3" catalytic would give the engine sufficient backpressure, wouldn't it?

 

I think the turbine of the turbo gives the engine all the backpressure that is needed.

As I recall, although my physics days are LONG gone, that resistance in a pipe varies according to the radius cubed. Small differences in radius make big differences in resistance (AKA backpressure).

 

yeah, I was always under the impression that a turbo car works best when there is as little backpressure as possible. Like david says, that turbo slows the air down plenty.

 

With a 3" exhaust you will loose alot of low end and gain alittle top end of a 2.75. I would go 2.5" ona k03 or k04

 

i got 3 inch on my 2002 a4 t and it hauls ***!

 

I had a 3" on my ko4 but couldnt stand having no low end