Welding exhaust question

[Schmieder]

I know how to weld.

What I need to know is if it is ok to tack up an exhaust pipe while still in the engine bay? Will it damage the PCM? The electrical surge of sorts? Other sensors at risk?

I will have the ground wire on the same pipe welded.

Using a Mig welder no gas (flux core). I have to join the wastegate to the down pipe. All the pipe is welded up except for the very last seam. And this seem needs to be perfect. To hard to mark and weld off the vehicle, it won't bolt up right. Even 2mm off can cause a problem, I know, I had to cut the last weld out.

I'm going to cover the engine and set up to only expose a small section where I'm welding.

My only real concern is surging electricity into the engine bay. I know it will ground into the ground contact wire, but not sure if it will cause any electrical spikes or EM fields that could harm sensors/pcm, ect.

....help please

[Azrael]

As long as the welder is grounded good you should be ok. To be safe I'd yank the battery out entirely to prevent igniting any gases it might be venting. And you can always just unplug the PCM and tape up the positive battery cable to be extra safe.

[Schmieder]

As long as the welder is grounded good you should be ok. To be safe I'd yank the battery out entirely to prevent igniting any gases it might be venting. And you can always just unplug the PCM and tape up the positive battery cable to be extra safe.

If it can be done utilizing safety precautions, then I'm good to go. Thanks!

All I need is 3-4 good tack welds. Then I can pull it out and finish the weld off vehicle.

[robertisaar]

yeah, disconnect the PCM plugs and the battery and any other sensitive electronics you come across(ABS, airbag, etc)

[Superdave]

the battery will actually absorb any voltage spikes from welding. No exhaust shops disconnect the battery or ECM, i never have either.


You'll be fine, just make sure the fuel lines aren't leaking and you put wet towels over anything that you don't want to get spatter on.

[pocket-rocket]

I did part of an exhaust on a Festiva and never unhooked the battery after my friend telling me he never did working in a wheel chair lift van conversion place. The Festy had no problems firing up after that and the radio still worked

[geoffinbc]

Yup you will be fine. Just make sure your grounded. With what your welding I doubt you will even exceed 24 volts.

[ForcedFirebird]

I never disconnect anything either.

Just make sure you don't weld in such a way that you can't get your part back out of the car lol.

[bszopi]

Just make sure you don't weld in such a way that you can't get your part back out of the car lol.

Although not welding nor car related, I can think of 2-3 things I've built for my house before that I couldn't get through the door when it was finished.

[Weatheralls Auto]

^^^^^
Lol, I built an Ice Fishing hut when I was a kid, it was beautiful till first ice hit, then I realize it was to big to get out of the garage lol.

[Schmieder]

Just make sure you don't weld in such a way that you can't get your part back out of the car lol.

Hahaha, that would be funny.

I thought about that in the very beginning stages when the turbo project was just on paper, computer text file actually.

I purchased two 2.5" bolt ups for the exhaust. 3 bolt with flanges type of thing. This way I can weld one in just before the pipe leaves the engine bay.

The next exhaust piece will be the flex pipe and test catalytic (clean 2.5" piping with no cat material inside, way better then a punched out catalytic. Punched catalytics still have flow restrictions.) That piece will run down and incorporate the first bend in the underside exhaust.

After that it will be the Cherry Bomb Resonator Muffler, then a Y leading to 2 x 2.5" lines going into Flowmaster 40's.

So my exhaust system after the turbo is divided into 3 parts.

(1) Post Turbo with heat wrap, Wastegate merge and WBO2/NBO2.
(2) Flex Pipe and Catalytic, downstream O2 disabled but present for emissions.
(3) Muffler System

I was able to maintain all mandrel bends w/o welding up any loss in angle, i.e. a bad cut through angle piece.

I learned a great trick while mapping the pipe. I needed the pipe to be lowered by 1.5" and had to be very, very accurate. So I got a straight edge and measured where the angle point was when the inside bend rose 3/4" from the starting flat side. Made two pieces so the other was the opposite in direction bending.

It worked very well! The down pipe weaves through the engine bay very nicely. And it had to if I didn't want to relocate braking components. I'm sure many know what exactly I'm saying.

[pocket-rocket]

Just make sure to protect your braking components somehow from the heat, be it header wrap, ceramic coating or heat shields. Boiled brake fluid before you even hit the brakes is no bueno (wow, firefox spell check doesn't know Spanish, lol).