Going to be modifying my exhaust so I'll need to weld it .......... i've got the welder, i've got the stainless wire, i've got bottles of pure co2 and pure argon ......

Do I need to change my liner?
Which gas do I use (do i have to change to CO2/Argon mix?)

Use pure Argon

Using CO2 can embrittle the weld. Apparently the Carbon in the CO2 is absorbed into the welded joint.

Don't know whether you NEED to change the liner but I didn't.

Welding tip needs to be the correct size for the wire you are using. No need to change liner. Use Pure Argon.

David

Argon, lower amps, slightly faster speed of advance while welding. Suggest u practise on a couple of scrap pieces before u commit
Shug.

Change the liner for ally (teflon) but not stainless, pure argon for stainless unless you are welding 5mm+ in which case argon with a 2% oxygen to help the penetration

thanks guys, knew i could rely on you lot ........

looks like once i've moved my engine bay side triangulation i'll be modifying my lolocost exhaust to exit a little lower !

Whooohooo, i'll be so happy, have never been happy that it exits half way up the chassis!