Custom Exhaust MIG GAS

hacadacalopolis · Thu Jul 10, 2014 2:28 am

I have some 3" 14G aluminized tubing that I am considering adding SS to the mix.

Other than the mock-up and fabrication of the downpipe to fit in given space; My exhaust build should go smoothly.
My plans are to either weld straight through or weld flanges for the CC( Cat Converter), As with muffler setup as well if I cannot purchase it flanged.

The cat is a spun metal magnaflow, which I am sure is all stainless body correct?
http://www.ebay.com/itm/3-Magnaflow-Uni ... 61&vxp=mtr

So Downpipe> Flanged Cat Mid-Section > Flanged Muffler is ideally what I am looking at if I can get hangers to accommodate the fit-up.

I have heard of a very low C02 with Argon Mixture can be used for welding SS to MS. Since I know of only welding once with TIG on stainless, I do understand that heat input on SS can weaken the chromium content to an extent. So, don't hang around in puddle...
What I have is a 2lb spool of weldcote .025" ER308L wire that has been inside all this time moisture free. This is what I plan on using.

To get to the point; After I prepare the MS to be joined to the cat, What is an appropriate gas to use? Argon 100%?
I am going to try and get all my MS welding out the way first so I can use up all the 75/25 mix I currently have. Is it a good thing to try and weld the entire exhaust with the 308L wire to increase corrosion resistance? Or will it just become a waste?

hacadacalopolis · Thu Jul 10, 2014 2:36 am

Oh another thing to add too;

Since it looks like I will be doing some all position welding, Would it be a good idea to push or pull? Especially for overhead if I have to.

hacadacalopolis · Sun Jul 13, 2014 8:57 pm

I was hoping someone would reflect some of their experience on this for what type of gas to use for joining mild steel to 304???

Instead of using 308 wire I actually bought 309L for this

I have been leading towards the 98% 2% Argon/Co2 or the Tri Mix. Can anybody give me some clues maybe?

Superiorwelding · Sun Jul 13, 2014 9:55 pm

First, I am sorry no one has answered your questions. I saw it the other day and never got back to it.
There is nothing wrong with using up your SS wire on your exhaust, which is what I assume you are doing. I would be cautious about welding with the stainless close to your manifold or header, especially if a turbo is involved as I feel your HAZ will crack over time. For your gas here are a few things to keep in mind. I use the helium trimix for almost all my mig SS. Using anything over 2% co2 WILL cause the weld to rust so I would advise agsinst the 98/2. However, it is exhaust and will rust over time. I think the areas around the welds will rust with this use anyway. Your gas will also depend on your budget. A trimix is VERY expensive and for a hobbiest doesn't warrant it's use. And last, the SS wire will run best on a trimix but can be used with other gas mixtures. Also, you mentioned earlier the use of 100% argon. In mig welding this is only used with aluminum.

But.... With all that said it is still just exhaust, many will weld it with what they have and it will last a long time.

As for push or pull, that will depend on your skill level and your settings. I wiuld try to drag it first and see how you like it.
There are others that will jump in on this one, RIGHT GUYS

-Jonathan

hacadacalopolis · Sun Jul 13, 2014 10:09 pm

Thank you Jon.
I have never ventured into gas for ss, other than tig.
From what you said I think I'll go and try the tru mix. Got any idea to $ for 80cf in fl.

If I misinformed, I meant to say I have used 100% argon on tig ss.

Superiorwelding · Sun Jul 13, 2014 10:13 pm

I don't know exactly but for a 125 cu ft bottle it was in between $100-$150 and they do not last long.
I would be interested what others have to say about this as well. I hate to lead you into a trimix that is pricy for no reason.
-Jonathan

hacadacalopolis · Mon Jul 14, 2014 1:47 am

Its ok. I was just looking for an average.
I'm not really worried about the cost. We do have a WESCO fill station in Pensacola. One of the guys there might be able to do something for me ( I doubt it), But I really don't know...
I'm more concerned about the gas characteristics for joining dissimilar metals.

Mon Jul 14, 2014 7:29 pm

If you were welding something that didn't take heat cycles like this, I'd say use the 75/25. I've done this.

I don't recommend it in an exhaust system, though, for reasons previously noted.

If you want economy, find a way to do it all in mild steel. If you're "married" to the stainless, use the 309 wire and the tri-mix.

These are the best options I see based on the information you've given.

Steve S

hacadacalopolis · Tue Jul 15, 2014 5:56 pm

Thanks for responding to this Steve.

Tue Jul 15, 2014 7:00 pm

Actually, re-reading my response, it wasn't much of a response.

300-series austinitic stanless steels show improved properties at lower temperatures, thus their choice for cryogenic applications like at my job. 300-series rods have the same properties.

400-series stainless behaves more like carbon steel, becoming more ductile with heat. I believe the MagnaFlow exhaust systems are built from 400- SS, and when welded with a 400- rod will have more consistent heat-cycle properties.

I may have to dig a litlle deeper before I "stand by" my answer...

Steve S

brokeitagain · Tue Jul 15, 2014 10:07 pm

I can say as a mechanic don't bother mixing aluminized pipe with a catalytic converter there is lots of info about this out there. converters are made out of stainless for a specific reason, does anyone have a link as to why??

Wed Jul 16, 2014 7:00 pm

brokeitagain wrote:I can say as a mechanic don't bother mixing aluminized pipe with a catalytic converter there is lots of info about this out there. converters are made out of stainless for a specific reason, does anyone have a link as to why??

Catalytic converters concentrate a great deal of heat. You'll often notice a heat-shield around it, where the inlet and outlet piping have none. While not all catalytic converters are stainless, it's a choice that reduces rust-through on steel that takes that much heat. As long as the inlet and outlet pipes are long enough to disperse the heat, welding "aluminized" is not an automatic "fail".

My preference would be stainless throughout, but for some, economy is the more important choice.

Steve S

brokeitagain · Wed Jul 16, 2014 8:19 pm

I install lots of cats at my shop, unfortunately I have to use aluminized pipe, customers almost never want to pay extra for stainless pipe, which is fine for me, I know they will be back in 2-3 years to pay me to replace what rotted away because they wanted to "save" money

hacadacalopolis · Wed Jul 16, 2014 9:30 pm

What more do you guys think about me getting some stainless straight pipe for the cat?
Brokeitagain makes a good point considering his related work experience.

I am leaning towards one more turn; Which is 304 V-band clamps instead of traditional triangle or 2 bolt flanges.
I will have 3 welded starting with turbine exit( vband machined into housing), then two clamps to separate cat and muffler.

brokeitagain · Wed Jul 16, 2014 11:03 pm

hacadacalopolis wrote:What more do you guys think about me getting some stainless straight pipe for the cat?
Brokeitagain makes a good point considering his related work experience.

I am leaning towards one more turn; Which is 304 V-band clamps instead of traditional triangle or 2 bolt flanges.
I will have 3 welded starting with turbine exit( vband machined into housing), then two clamps to separate cat and muffler.

I must have missed something, if you are running a turbo then stainless is almost a requirement, aluminized mild steel is the worst possible choice even for heat shields when turbocharging is involved

hacadacalopolis · Wed Jul 16, 2014 11:32 pm

Dang,I was hoping you weren't going to say that.
I have in laid in a pile a fab builders kit of 14G aluminized MS 2.5" mandrel bends. Bought over a year ago. This was my ticket to a small project with the help of a HF bandsaw.
For temperature concern; My plan was to wrap the downpipe and manifold with fiberglass wrap that is used on headers...

I see a lot of the 409 16g out there for the bends I need... What would you recommend brkitagain?

brokeitagain · Wed Jul 16, 2014 11:39 pm

hacadacalopolis wrote:Dang,I was hoping you weren't going to say that.
I have in laid in a pile a fab builders kit of 14G aluminized MS 2.5" mandrel bends. Bought over a year ago. This was my ticket to a small project with the help of a HF bandsaw.
For temperature concern; My plan was to wrap the downpipe and manifold with fiberglass wrap that is used on headers...

I see a lot of the 409 16g out there for the bends I need... What would you recommend brkitagain?

409 and don't bother with header wrap unless its possibly burning/melting something

hacadacalopolis · Wed Jul 16, 2014 11:44 pm

Thx for your addition to this.

I'm assuming 409 is suitable enough for rust resistance to meet my needs.
Rather than the more expensive 304.

brokeitagain · Thu Jul 17, 2014 7:48 pm

hacadacalopolis wrote:Thx for your addition to this.

I'm assuming 409 is suitable enough for rust resistance to meet my needs.
Rather than the more expensive 304.

I believe most factory exhaust is made from 409 stainless, but I have never gone very far as to find out for sure

hacadacalopolis · Fri Jul 18, 2014 1:56 am

Seems to be, I have been reading up on some of this. Even most of the magnaflow cats and mufflers seems to be the cost effective 409.
I'm seeing Borla quite possibly being more on the quality side of tubing.