'84 Audi Coupe Gt grp2

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'84 Audi Coupe Gt grp2

Postby Afterthought » Fri Jun 11, 2021 6:11 am

Man that looks great . So difficult welding all those in the car . Props for taking that on.

A common thing to run into is when you are closing up the last bit of the hole on a tube that’s welded on both sides , there are no more gaps for the remaining gases to escape ( besides the one you are welding) so the escaping gas blows away your shield gas. Similar to if you were back purging and didn’t have a vent hole .
What people do usually in this case is preemptively drill a hole with a diameter of 1/8” or so which would be covered by the tube being welded over it, so that the tubes are all vented together - if that makes any sense .
But as you mentioned it could be any number of things . Inside not being clean , lack of shield gas , or possibly too much purge could draw in oxygen . If using tig I don’t know what type of size of cup you use but I like to use one that has the diffuser in it , that way you can turn shield gas way up if needed but without a ton of turbulence or velocity .
Posts: 1232
Joined: Jan 16, 2014
Location: Bellingham, Wa

Re: '84 Audi Coupe Gt grp2

Postby mrdeye » Fri Jun 11, 2021 10:51 am

Thank you and thanks for sharing your knowledge. The whole cage will be mig welded with .035 wire, 75/25 mix and the nozzle on the end of the gun is a 1/2 opening. I thought of putting a vacuum at a joint/opening away from the joint I was welding to pull any gas away, but also thought that might creat another problem and like you said thing start to seal up. I like the 1/8 hole Idea. What if the hole was drilled a little farther away from the joint so that as the joint is completely filled there is still a place for gas to escape and then fill hole and smooth out? It’s only an 1/8 hole, but what kind of effect would it have on the cages structural integrity with 1/8 holes in multiple places? Everything effects everything. One thing at time. I’ll lay some welds down and see what happens with having the regulator at right setting.

Thanks for your time and input!
Daily driver: '01 Toyota 4Runner
Project car: '84 Audi Coupe GT
Previous cars:
'95 S6 Avant, '87 5K TQ, '95 VW Golf, '84 VW Jetta turbo diesel, '84 VW GTI
Posts: 151
Joined: Nov 13, 2016
Location: Colorado


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