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Im not an expert on welding, would I have a problem welding plain steel like this
to the middle of stainless steel like this
?

What kind of welding process?

Welding stainless generally is harder than welding mild steel, but people do it all the time. In this case, be careful about distortion -- stainless steel and mild steel expand different amounts when heated. You'll probably need to use stainless filler rod to make sure you get enough fusion on the stainless side, and to handle whatever distortion you do have. Be sure to get a kind of stainless rod that will also work well with the mild steel; you don't want it alloying badly into something that will rust fast. Whoever sells you the rod should be able to help.

That's about all I know... I've never welded stainless myself.

You want to try to stick the Magnaflow cat in the middle of the Perrin downpipe? You have to do that to pass emissions? There's a cat in the midpipe, right? The Magnaflow put in that position ought to do a good enough job of cleaning up your exhaust.

It kind of seems like a shame to take that beautiful downpipe, slice it in the middle, and burn the ends welding in mild steel.

Im not really interested in how it looks. This downpipe is ALSO the mid pipe! Ill end up putting it into the stock location. I could probably pass without it but I dont want to run catless. With an exhaust of this size and the power levels Ill be at Im willing to bet performance to be equal with or without the cat, so why not have an easier time with smog and just install one?

Even before choosing this specific pipe I had planned to make the entire exhaust black. Im not a fan of looks in any way, I was even considering using the NA hood on my car because I didnt want the scoop. Heat considerations cancelled that plan.

I have a full turbo back exhaust waiting to go on and the only cat is between the dp and the mid-pipe.It's dp,cat,mid-pipe,muffler and tip.Is that for a wrx?If so it will be about 5" too short of the axle back muffler portion so why not cut the flange off shorten it a little more and put the cat between the mid-pipe and axle back then install a o2 sensor bung in dp portion?One weld instead of two and you wont have to lengthen o2 wire.

The entire exhaust will end up being custom, 3 inch+ from the turbo to the tip. Mandrel bent all the way too so I will have many more welds. That makes sense though just to cut the "tail" off and attach it.

I plan to use the NA oxygen sensor anyways and put the 02 sensor just before the bottom bend of the downpipe. The NA 02 sensor wire is pretty long.

A vendor contacted me with the price of 390 shipped for the DP, not bad!

I cant wait. I only wonder how long away my smog referee appointment is.

sounds like a good deal. As far as welding those dissimilar metals, there should be no problems if your welder knows his welding rods and temps. If your interested, the guy who helped me is in Redwood City and is really helpful. And, My car just passed the smog test!

I'm a welder in a fab shop here in SW Wash. I join SS and Mild Steel all the time, using a wire feeder with either wire works fine. Personally, I'd use a SS wire, and then after the welding is done, wipe it down with WD40 or something of the likes to keep rust from forming. V8 street rod guys build custom pipes out of boring old mild steel, and wipe down with WD40 occasionally to keep rust down.

Anyways, you shouldnt have a problem, they're both ferrous carbon steels, they'll join fine.

Erik

also a welder here, you shouldnt have any problems welding stainless to mild. rust would be the only issue, when heating the metals up so much, and mixing them, youll make the mild steel extremely vulnerable to rust, as much as two or three days you see rust starting to form...
as everyone else has stated, definatly use stainless filler rod, and i would have it TIG welded if i were you, its a much better weld.....strength and appearence wise....
Good luck!
Sam

Sport Coupe Erik wrote:I'm a welder in a fab shop here in SW Wash. I join SS and Mild Steel all the time, using a wire feeder with either wire works fine. Personally, I'd use a SS wire, and then after the welding is done, wipe it down with WD40 or something of the likes to keep rust from forming. V8 street rod guys build custom pipes out of boring old mild steel, and wipe down with WD40 occasionally to keep rust down.

Anyways, you shouldnt have a problem, they're both ferrous carbon steels, they'll join fine.

Erik

has anyone suggested having flanges welded on and bolting the two together? just a thought to avoid some of the rust issues.

my thoughts exactly.

I didnt want the cat so far down the exhaust. I may end up doing it though.