Welding exhaust piping

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Hey all,I am finally getting around to welding up the exhaust tubing on my car. My main question is, are there any major prep/techniques needed to get the job done? The pre turbo exhaust is stainless and the post turbo (downpipe back) is regular exhaust tubing. I see a lot of people bevel the ends before welding and I also see others just clean the ends and weld them up. Also, some butt the pipes with no gap while others leave a small gap between for the filler.Thanks in advance,Kyle
Reply:When I owned the exhaust shop we would clean the ends prior to welding and after coping for angles prior to welding on both stainless, and galvanized/aluminized steel tubing. The wheel was a non woven wheel on an open faced pedestal grinder and worked very well with good durability. We never beveled anything as the tubing was usually 16 guage and we used either .030, or .035 ER70S-6 for steel, and some 400 series wire for stainless. The finished welds were then sprayed with a high temp galvanizing compound. Stainless was left as welded.SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:Really appreciate the detail and advice! How about figment/butting together? Do you leave no gap or leave a gap (say.030) for the filler?
Reply:No gaps on purpose. I had three SP-125 Lincoln welders with carbon steel wire, and a Miller about the same size with stainless. We always used "Stargon" gas with carbon and I can't remember the mix for stainless. Been too many years and memory is fading.....SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:you make no mention of thickness.  Some like to use thicker stainless pipe  (schedule XX) for the part leading into the turbo.  If you are doing the same, then I suggest you look around some Google Search Images---some like to bevel the pipe to get good penetration while keeping the amperage just a tad lower than normal. 1st on WeldingWeb to have a scrolling sig! HTP Invertig 400HTP Invertig 221HTP ProPulse 300HTP ProPulse 200 x2HTP ProPulse 220MTSHTP Inverarc 200TLP HTP Microcut 875SC
Reply:Don't forget about back purging the stainless inlet pipe w argon.
Reply:Sorry, left out all the info on my part. The piping isn't sch so I am going to assume it is 304 stainless. From the headers it is 2.5" before the 2-1 collector and t6 flange so heat should disperse pretty quick. I am using the kit that was previously a t4 uneven setup. The passenger header faced towards the rear and the pipe ran around the back of the engine by the bell housing and met with the other header right in front of the steering knuckle. To me this is a bad design, so I am running two forward facing headers that will collect together beside where the battery sits (2000 camaro, battery relocated). I am using a tig 1/16" lanth setup with a #8 stubby gas lens. Many people say stainless needs a lot of shielding so should I use a larger lens?
Reply:Just to add a little.304 isn't the best stainless for turbos.  321 has better characteristics when it comes to heat.  Its also a bit easier to weld (less sensitive to carbon).  347 filler.  When polished, it has a slight gold/straw color that I think comes from the titanium its alloyed with.If the exhaust manifold will hold up the turbo (no other brackets) you will want a full penetration weld.  That means back purging the manifold or using Solar Flux.  If you aren't supporting the weight, a close fitup (a good idea anyway) and autogenious welding (no filler) for the first pass and you can get away without back purge.  For a bit more strength, a second pass with filler - just to level weld.  If the gaps are too large, and you find yourself adh ding filler - you will have ugly, air flow reducing, buggers on the back side.  These are particularly hard and require grinding to get off.  Bottom line, if you try the autogenious method you really need to pay attention to the puddle.   That second pass with the filler needs to be done equally carefully.  If you get it too hot, it will reflow and potentially be exposed to air on the back side.As for gas coverage on the front side.   Even when working with thin electrodes, use a No 7 or No 8 cup.  Shielding gas flow rates closer to 15.  I only have gas lens collets.  I find that when welding stainless, it all looks pretty until I hear the gas valve snap closed - then it instantly turns blue or even gray.  The dynasty has an automatic setting for the gas valve that I believe is too short for stainless - it protects the tungsten only.  Assuming your going to run about 50Amps, I'd say 8 seconds post flow.This is a great excuse to run a cheater lens - at least for my middle age eyes - and get really up close to the weld and see what is happening.Stray color is the goal, red/salmon color is OK, blue is on the edge, gray, you might have overheated it (often you can polish it out).As for single turbo setups.  If you don't have room to put the turbo right in front of the motor (how far is that radiator tilted?) every path from one engine bank to the other seems to have compromises.  Run it up front and you are near the steering rack, harmonic balancer etc.  In front of oil pan sump?  Does the oil really need more heat?  And, in your case, back by the transmission - path gets long and automatic transmissions are killed by heat.  Consider getting it ceramic coated inside and out to try and keep the heat inside the pipes (heat == energy, you want to spend energy spinning up the turbo - not heating the surrounding air).BTW, is this with intercooler?  Is there enough room to run intercooler + A/C condensor?  I have a '95 and have been scheming a way to fit twin turbo (if I can figure out the accessory drive - might be cheaper just to go with LS style engine).Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX