All the techniques are applicable to any exhaust component for any car.
Utilizing a OEM downpipe/cat I built a weldment jig to help make it plug and play into the car.
Making use of an inherited strongback, I add some features to locates the flanges
The plan was to keep the turbo interface and the mid pipe interface in the same place and stay within the envelope of the OEM.
Genuine Saab had the turbo flange so I used his, but had to machine the lower flange.
Lots of fitting to find the sweetspot and piece by piece tacking.
Argon back purge the inside of the tubing for nice clean welds and this keep the corrosion and strength proprieties of the stainless. The little black blob was from the tack in open air.
Welding thin wall .063 to .375 flanges take a lot of practice to control the arc and the heat. It is challenging to get a nice puddle on the flange and the tube without blowing a hole in the tubing. I used .035 308L filler rod. Also stitch weld,(1-2 inches) jumping back and forth across the tube. Don't be tempted to start in one place weld all the way around in one continuous pass.
Final tack while back in the jig. The elbows slip into the cat, so this leaves some fudge factor to get it dialed in if the parts twisted, warped, grew, or shrunk during the other full welds.
You can also see the cardboard and outline of the OEM cat in the background. A little bit outside the box, but I think I'll be good.
Money shots:
Still need to add the first and second O2 bungs. Then the moment of truth, does it fit?
