Newbie to welding & forum - MIG question

[00GTS]

Newbie to welding and this forum.

I have some exhaust work to do on one of my cars and I decided that I would try doing the work myself.

Picked up a 120V 90A inverter stick/MIG welder and I've been practicing beads on some 16 gauge plate. Flux-core wire (.030) only so far. Steep learning curve but lots of fun!

What I am planning on doing is replacing the catalytic converters on my car with hi-flow versions. This will entail welding 2.5" to 3" adapters onto the cats. The cats are stainless steel and the existing exhaust is not. Will be lap joints.

Get I use flux-core wire here? Better to go with shielding gas? What type of wire?

Any advice would be great!

Thanks.

 

[00GTS]

Sorry, 140A unit......90A at 30% duty cycle.

 

[Cobbler]

Forget the flux core wire, get yourself some gas, preferably argon/co2 mix or just plain co2, bit more splatter with that. In UK a lot of people use co2 pub gas, but you have to be careful that its just co2, a lot of beers now use co2/nitrogen mix to give a better head. I don't know what is available in Canada. Regarding the wire, there is no point in buying stainless wire if your joining it to mild steel, I would say just use ordinary mild steel wire, that's what I would use, but someone with a better understanding of the make up of steels may come up with a better suggestion. If the adaptors are stainless, so it is stainless to stainless at this point, it could be worth getting stainless wire for this, but I can't say, also I'm not sure what gas you would use. I've used mild steel wire to mig stainless, I know it not ideal, but it works but may not be as strong. A lot of the early stainless exhausts had mild steel welds.

Good luck with it & get a bit of practice in before you start.

 

[00GTS]

I figured C25 gas was the way to go. Often called AutoWeld here. Should I use .030 wire??

Adapters are not stainless. Configuration from engine block will be: 2.5" exhaust pipe -> 2.5"-3" adapter -> 3" cat -> 3'-2.5" adapter -> 2.5" exhaust pipe

Current cats are 2.5" inlet/outlet, but I got a smoking deal on a lightly used pair of 3" hi-flows.

I have to do this twice (dual exhaust) as well.

Yes, lots of practice first. I'm going to buy some extra adapters and some piping to practice welding the joints. Running beads on flat plate will only get me so far.

 

[Cobbler]

We use metric wires here, I think 0.30 is equal to 0.8mm, personally I would go for 0.6mm, but someone else would say 0.8 would be my choice. The tendency is to go for the thinner wire for thinner metal, but some say they much prefer the thicker for everything. If 0.8 was what I had, I don't think I'd buy 0.6 specially, I'd use whatever I had, try on a bit of scrap pipe & see how it went.

That cat doesn't look stainless to me, looks silver painted. If it was stainless why would they paint it?

 

[00GTS]

0.8 m is correct. We're officially metric as well, but most of the products are produced in the U.S. so we use imperial interchangeably.

The cat extensions (reduced diameter at each end) are stainless (verified with a magnet). Center section is non-stainless (magnetic). The diameters are also slightly different at either end, just to add to the fun. One is 3" ID and the other is 3" OD. It may be that these were installed on a stainless system previously and those extensions are the remnants of that system.

You can see the size difference between the OEM cat and the hi-flow. Will be substantially lighter.

I may just weld one end (engine side) and clamp the other. Will be buried in an insulated sill cover when it's all done, so I'm not concerned about how pretty they look!

 

[chris y]

Small point that might be of interest, most exhaust stainless is magnetic.
Non magnetic is a sign of very good stainless such as 304 but lots of other grades are used that are magnetic.

Of course paint is indeed a sign of not being stainless though.

 

[Cobbler]

What is the vehicle, it sounds interesting. A picture or two might be a good plan as I presume it's Canadian or American & we may not recognise it over here. Anything with 2 21/2 inch exhausts sounds a pretty hairy beast. A small intro on the members part of the forum would be good, so as we know who you are & and interests etc.

You say Canada is metric, but most of you stuff is imperial, sounds a bit like here, officially been metric for years, but most of us think in feet & inches, us .... err um... older ones do anyway.

 

[00GTS]

I'm sure you'll recognize the car.....

Also, since my last posts I've switched out my inverter welder for a Lincoln Mig-Pak 140. I had picked up some C25 and the gas wouldn't flow through the inverter's hose. The store even priced matched the more expensive unit, so I didn't have to pay more. Bonus!

Just ran some beads with gas. What a difference!

 

[Mick B]

Welcome to the mad house OOGTS, Oh and while I think of it ................ can I have your car when you die !?
I have seen them racing and apart from the racing Bentleys they sound beautiful at full noise.
Is your's a V10 or is that the only way they come ?

 

[00GTS]

2000 Viper GTS, 8.0 L aluminum V-10, 460 HP, 500 lb/ft. Mine has about 60,000 km on it. I've owned it for close to 4 years now. Only modification has been a muffler delete.

V-10 is the only way they come.

The hi-flow cats that I'm planning on installing should add about 10 HP or so. The main reason is to decrease the heat in the sill area. The heat is starting to discolor the paint on the sill covers over the existing cats, and you can easily burn your leg getting out of the car if you're not careful. New cats should change the sound slightly as well.

 

[Jim Davey]

I have a die cast Viper in blue with the White stripes in my office as I love the shape so much. The curves on the bonnet are outrageous. I'm Envious of you but I wonder what they are like to drive? Heavy is what I've heard?

As for your cat replacement, two schools of thought on this, the one I subscribe to is use 309 mig wire, or stick weld with 309 or 312. Or, you could do what most exhaust shops do, which is mig weld it with ordinary mild steel wire. This is not reccommended practice and has been discussed on here before but it does seem to work, especially in a sleeve joint application where the weld is supported.
As I say, options, I've got access to TIG, and the correct dissimilar joint fillers, so I'd use that, scratch that, I'd have made a full stainless system lol, but if I had to fix yours, I'd go with the right metals, 309 or 312.

Hope this helped.

 

[arther dailey]

Somehow I dont think you will notice 10 hp differance with the poke that puts out, you might notice the noise differance though. Nice.. arther

 

[paceman1]

never had a cat on my evo 8 made a jig for de cat i ran 3inch system all through 532bhp 470torque safe map
free flow cat is good less back pressure for the engine so it will breath better no cat evan better
nice car

 

[arther dailey]

I have read on another forum, cut cat open,gut it, weld it back up and re fit...not exactly legal me thinks,but..

 

[Jim Davey]

I have read on another forum, cut cat open,gut it, weld it back up and re fit...not exactly legal me thinks,but..

Better to buy some flanges and make the cat removable and replaceable for inspection time, then bolt in a de-cat pipe the rest of the year.

 

[paceman1]

no cat
but if you get caught with no cat

 

[00GTS]

Time for an update.

Exhaust has been installed on both sides. Went pretty well with the exception of one area on the backside of the pipes near the front connection. VERY difficult to access. Ended up using flux core (because the tip was smaller) and making a bit of a mess on the back of each. I also had to touch up a couple spots that had small leaks when the car was running, but all seems good now.

Opinion on the weld? First attempt at exhaust piping!

Primary reason for this mod was to reduce heat in the sill area. It worked. You could fry eggs on the sills before, but now you can rest your hand on the sill while it's idling. The extra hp is a bonus. Car sounds a bit better in the upper rpm range now and seems to rev a bit easier.

No chance to remove the cats altogether as emission testing in Ontario is mandatory. Testing has changed from a "sniffer" and dyno, to a strictly OBD test. I COULD install O2 sensor "simulators" to fool the computer, but apparently the smell of a catless engine is pretty bad. Supposedly the rear fascia gets pretty messy from the exhaust as well. No thanks.

As to the questions of how the car is to drive? It's a handful if you're not careful. With no ABS, traction control, stability control, etc., it doesn't suffer fools lightly.

Handles very well (0.98 g). The steering has a fast ratio but is a bit numb (275 mm front tires). 3,380 lbs. 49/51 weight distribution.

My biggest gripe with the car is the interior. Seats are great, but everything else is cheap plastic. Console, dash, door panels, everything!

Anyway, I'm way off topic here! This is supposed to be about MIG welding. LOL

 

[Jim Davey]

Your skills with a camera (if you took the shot of the car) are better than your skills with a MIG torch But the job wasn't easy to access and exhausts are never easy under the best of conditions, so doing it in position with Flux Cored isn't something I'd wish on my worst enemy, well done.

 

[Jim Davey]

There isn't any smell to a cat-less car in my experience, but the flames and pops are usually a dead giveaway to anyone in the know.