$teady$upreme

i konw the difference in appearance, but wat's the difference in performance wise?? let's say both in 2.5".

Yippers®

(or more)in flow area depending on the degrees of bend and the radius.

BoostLad

but none of the bends on the A4 are sharp enough to get that much of a decrease. As exhaust systems go, its a pretty straight shot, so the loss w/ a non-mandrel system is not as bad as it could be on another car. To compensate, just go with a slightly larger diameter- if you want a custom system to compare with a 2.5inch mandrel system, use 2.75inch piping in a crush-bend system. I have a 3inch crush bend system (custom) that flows much more than my old 2.25inch mandrel bent borla.

$teady$upreme

but i am running a stock turbo with chip and some basic stuff, so u recommend me to get the 2.75 in a crush bent system rite? coz no one can do mandrel bent here in Vancouver BC. also wat steel of your piping are u using? stainless or aluminized steel?

BoostLad

yes i am. Three inches for you would prolly be overkill, but 2.75 would be fine for you. I'd estimate the flow of a crushed 2.75 to be similar to a mandrel 2.5 (rough estimation, i have no facts about that). Best thing is you could prolly do it for way less than a mandrel bent 2.5 inch system. As for metal, i used aluminzed pipes, but stainless steel components (SS muffler, resonator and cat, and SS flex piece). Below is my post when i had the system done...<ul><li><a href="https://forums.audiworld.com/a4/msgs/1282571.phtml">custom exhaust</a></li></ul>