Custom exhaust questions. (1 Viewer)

[MikePL]

So the time has come to change my exhaust. The stock one is so full of holes that I can see through it sideways. It no longer attracts magnets because there is no more steel, just rust. With such a scenario there's obviously nothing to weld. My Y pipes are also a bit punctured. And to make matters worse, I don't have access here to all those funky Manaflow, Borla or EMS exhausts.

My only option is to fabricate the exhaust myself. I have some minor MIG welding experience, a TIG welder is on it's way, I also have a plasma cutter and some other tools. I also have access to 304 stainless steel.

My initial thoughts:

1. Make it a 3" diameter. The difference in tubing price is not so big.
2. The stock center muffler annoys me because it's huge. I am planning to use a muffler similar to the 'Moroso spiral muffler'. Does anybody have experience with this muffler design? My plan is to run the tubing and muffler on the outside of the frame so that I have free space for a gas subtank or maybe something else in place of the stock muffler. I would greately appreciate any comments on the spiral flow muffler design.
3. Go stainless from Y pipe to tip. With SS I will not have to ever think about the exhaust again.
4. I have two new Magnaflow cats. They are three-way and the universal type. I am planning to run two of those side by side to make sure I don't have much air restrictions. One O2 sensor before the cats and one after.


I am currently looking for criticism, inspiration or a pat in the back meaning that I am going in the right direction.

And one question: I've seen that many exhaust tubes are lap-welded. The tube ends are stretched so that two tubes connect and are welded around. I have no access to a machine which would let me stretch tubes so I will have to butt-weld them. Will it be strong enough?

Butt weld vs lap weld below:

 

[93Chewbacca]

I occasionally used an exhaust pipe expander like this:

Amazon.com: Exhaust Tail Pipe Expander: Everything Else

 

[MikePL]

Very valuable link. I will order one of these. Thanks

 

[MikePL]

So a little update is going on.

What I have so far:

- TIG welder, I am learning how to use it.
- tube bender (cheapo) will arrive soon
- 304 stainless tubes

I have a question about flanges. Do I need a gaket to make a flange/flange connection or maybe hi temp copper silicone will seal enough?

 

[jimep]

I have access to sanitary stainless from where I work (a dairy plant). since u have a tig try doing sanitary welds. involves purging the pipe with argon while welding, and allowing only a small hole for the gasses to escape. butttwelding is the only way to do it with the pipe we use, and benders don't work too well. most if not all will kink stainless. we weld all the elbows in. the v-band style fittings (we call them tri cLover connections because of the brand we use) work well for flanges if u use a pieces of filler wire as a gasket and can be rotated around 360*. make sure your cuts are square though.

 

[Bambusiero]

I would NOT count on getting good results out of those hand-wrench powered tubing expanders. I have one. I tried to use it. I would have to call it a failure.

The problems are these:

1) The ramp surfaces have to slide over each other for it to work. The metal needs to be hardened, and it needs good lubrication. On mine, there was enough force to create indentations (deformations) on the tool's ramp surfaces. That created even more friction than there would have been anyway. The tool basically locked up.

2) There was a LOT of torque involved. My biggest, longest cheater bar was not enough. The piece of tubing (2.5 inch dia, .072 inch wall) was clamped in the bench vice hard enough to dig into the metal and being squeezed and deformed, and it still was tearing out of the vice. FAIL!

If the tool pieces were cleaned up (filed flat) and case hardened, and well greased, it MIGHT work. However, Clamping the tubing is still a problem. I tried to case harden a similar sized piece of steel, but the 2 MAPP torches I have were not able to heat the piece to sufficient red heat. An oxy-acetylene torch would probably have worked, or a furnace of some kind. So, I have not gotten past that yet.

I have seen a professional version being used at an exhaust shop. It basically works on the same principle, but is electric-hydraulic piston powered instead of screw powered, so there is no need to clamp the tube at all. No twisting, just hand held. The operator steps on a foot switch and it's done in seconds.

Mark

 

[MikePL]

I've already bought the expander. I will grease it thoroughly with moly grease and see if it works

Jimep, can you elaborate on the V-band fittings. I cannot imagine right now what you mean. And the filler wire as gasket part...

 

[jimep]

Tri-Clover Ferrule - tri-clover ferrule, stainless steel tri-clover ferrule
heres a link to the furrels so you can get an idea what I'm talking about.. there's different style clamps you can use. I try to grab the high pressure ones that use 2 bolts that hold them together... and the filler wire is just bent in a circle to fit in the groove to fit between the 2 ferrels once they are clamped together

 

[jimep]

Commercial and Home Wine Making Supplies - The Vintner Vault
...and the clamps

 

[MikePL]

I have a question, or two. I see that my flange mating surfaces are so straight that they stick to each oher when wet. Do I need to fabricate gaskets for them or maybe a hi-temp silicone will be enough? And can I also trust when it's written 'o2 sensor safe'? Are they really safe? I am about to put new OEM sensors and don't want to destroy them...

 

[Kernal]

Would machining a shallow circular groove in the face of each flange be possible; then use a high temp o-ring/donut gasket?