What thickness stainless should be used for making a custom downpipe? I'm ok for a flange, just curious as to what to make the pipe from as the off the shelf downpipes look fairly beefy.
For performance - 3mm thick wall 316 back purged TIG welded if doing it properly. 304's good and cheaper but I would always go thick wall and back purge TIG to make sure there is full penetration so over 2mm.
I contacted PTR Exhausts in the UK and this was the reply: We use 1.2mm on our turbo exhausts including race versions on rally cars, but these are purged with gas on the inside when welded to make stronger joints, if not purging then 1.5mm would be better. Regards, Pete.
