Grassroots Exhaust Bending?

Thinking about putting a more free flowing axle back exhaust on my 500 Turbo. Apparently, you can even run a straight pipe and not affect the noise ratio too much.

Problem is, exhaust manufacturers think that Fiat owners have deep pockets. The one offering just the straight through pipe is asking $500.....

Trying to figure out if I could just bend my own and do it myself. It's easy to get to and remove, but the pipe is 2.25 inches in diameter and I'm not sure what to bend it with. Any grassroots solutions? Obviously, buying a tubing bender to handle that size would kinda defeat the purpose of staying cheap.....

-Rob

The old "fill it with sand, heat it with a torch, and bend it on your bench" comes to mind. Never tried it myself.

Figure out the routing and buy a couple mandrel bends, cut and weld together?

RossD wrote: The old "fill it with sand, heat it with a torch, and bend it on your bench" comes to mind. Never tried it myself.

Beaten, that's the method for DIY mandrel bends...or yeah you could buy mandrel-bent sections separately.

Moonshiners used to make a "snake", the coiled pipe used to condense the alcohol from the steam, by packing the tubing full of sand and bending it around a tree. The sand would keep the tubing from crushing..at least too much.

Here's a link on the HAMB about sand bending.

I like the old "buy a pile of mandrel bends and flanges from Summit and weld them together for $100" way of going about it myself.

The bends look like they'll be odd angles, like 15 degrees, 110 degrees, etc. Never bought kits like that, I always assumed they were simple bends. I'll do some checking. I've thought about putting a more free flowing muffler on it, but having trouble (in the few minutes I've had to search) finding one small enough that's not just a cherry bomb.

-Rob

rob_lewis wrote: The bends look like they'll be odd angles, like 15 degrees, 110 degrees, etc. Never bought kits like that, I always assumed they were simple bends. I'll do some checking. I've thought about putting a more free flowing muffler on it, but having trouble (in the few minutes I've had to search) finding one small enough that's not just a cherry bomb. -Rob

I usually buy two different radius donuts or elbows then slice the degree of bend that I need out with a band saw, tack weld it all together under the car and pull it out to burn it all in. It's tedious but the results are good (and cheap).

Looking at Summit, the kit's start at $200 up, but the individual pieces are under $20 each. We're talking about a about 2 total feet of piping, so I may mock up something and figure out which bends I'll need to buy.

I'm assuming no brick and mortar stores would carry them. Having a local place to grab the pieces or, in my case, replace the inevitable pieces I screw up the first time, would be nice.

-Rob

rob_lewis wrote: I'm assuming no brick and mortar stores would carry them. Having a local place to grab the pieces or, in my case, replace the inevitable pieces I screw up the first time, would be nice.

Any speed shop should have them, you might even find them at your local RiceMart.

OK, I've found a kit on fleabay for $69. Which has a bunch of bends and still cheap enough that if/when I hork it up beyond all recognition, I'm not out a ton of dough.

Next question. I can easily remove the current exhaust and use that as a template, but does anyone have recommendations for a mockup for on the car? Thought about just using a coat hanger, but that won't cover how thick the pipe would be.

Maybe I'm just over thinking it and could do it with the current exhaust.

-Rob

I once saw something that looked like a coat hangar stuck through a bunch of wooden hockey pucks to simulate the width of the exhaust pipe. I think styrofoam would be easier to build though.

Start with telling us what you DO have to work with?

torches, welders, hammers, wood fab skills and equipment (Make wood bender) trees, pulleys....?

What are your fab skills like? Mad or Mild?

I want to say the Abarth came stock with a straight pipe? Does anybody upgrade that and sell the stock one?

Giant Purple Snorklewacker wrote: I like the old "buy a pile of mandrel bends and flanges from Summit and weld them together for $100" way of going about it myself.

That's the easiest way I've done it.

Kenny_McCormic wrote: I want to say the Abarth came stock with a straight pipe? Does anybody upgrade that and sell the stock one?

yep, the Abarth exhaust is essentially a straight pipe. I dont know if the turbo is a single or dual outlet though. The Abarth turns it into a dual outlet along with corresponding cutouts in the rear valence.

NOHOME wrote: Start with telling us what you DO have to work with? torches, welders, hammers, wood fab skills and equipment (Make wood bender) trees, pulleys....? What are your fab skills like? Mad or Mild?

Good point. I'm not a master welder, but have done some MIG welding. Welds aren't pretty, but are functional. I'm getting better, but I think it's good enough to weld up an exhaust. My comments about messing it up will probably be more towards "measure once, cut twice" than "measure twice, cut once" mistakes. Although I own a new car, I've rebuilt British cars my whole life, so I'm less concerned about the skill sets I have and more about it's something new that I'm just trying to figure out how to attack.

The Turbo is a single exhaust, Abarth is double (an still has two mufflers, so not really a gain there). Plus, I'd have to change out the rear valance to match the dual mufflers AND would run into issues with the hitch on the car. I thought about it, but turns out some of the Abarth guys are going to a single muffler or pipe too.

I'd forgotten about mandrel bend tube kits, so I'm glad I asked the collective wisdom of the group.

-Rob

drop it off at an exhaust shop and let them worry about it..

In reply to novaderrik:

Thats a good way to get bad results, depending on the shop (in my experience is most all of them)

I just count the bends and buy "U" bends, cheaper than kits and exact degree bends by far.

Start by pulling all of the old exhaust you are replacing, chances are it won't be much help. You can buy sleeved ends of pipe that fit over both ends of pipe. I cut these down just enough to hold two ends and to let you play around with the angles. You can use unused jacks jack stand or get creative with wood for temporary support of the exhaust while you are fitting it. I just do little sections at a time any work back. I mark the exhaust on three sides on side with an "I" next with "II" and last with"III" in a "Y" pattern. Then tack with 3 welds in the same manner when fitment for that section is good. I just eyeball the cuts, cut shy and make up for the difference with the grinder. Make sure to grind a bevel around the cut ends of the pipe before you weld, and that ends fit flush before you butt weld. You will need at least a hacksaw, grinder, respirator,welder, a vice and a welding paint marker. And for cheap hangers rebar works well

I built mine with pre-built U-bends. It takes a long time, mostly due to getting back under the car to test fit everything.

Another vote for mandrel bends.

BUT! Check with your local muffler shop. They might surprise you. My local shop does indeed carry individual bends, and they're within a couple of bucks of the online prices. Plus I can pick up a whole bunch of them and return the ones I don't use. They like interesting projects. The shop in question is a big independent, not a chain. I don't know how much effect that has.

The cheap option is to raid the big scrap iron bin behind the shop. That's where all the old stuff goes, and if your town is like mine it's full of almost-new stuff that's been pulled off for a big noisy upgrade. Especially trucks. Ask first though.

I've seen header tubes that were done with the tube and sand method. Based on the results, it's harder than you think.

Built from scratch out of mandrel bends, including the headers.

how many bends are in an "axle back" exhaust replacement?

Watch what kind of mandrel bends you buy.. Don't always go for the cheapest kit... You'll get the thinnest cheapest pipe then that will rot out after a couple years... You want a good aluminized pipe that will hold up over time...

It was probably more than 10 years ago that I did a custom exhaust assembled from pieces, but when I've gone that route I've had local shops bend and swage pipe for me.

That let me get the angle and length I wanted and not have to have too many pieces to assemble.

For about $5 you can buy a goniometer from amazon and measure the angles on your current system to use as a baseline and then adjust to compensate for the lack of muffler. Just keep in mind the bend radius when there are multiple bends in series or the pipe is bending to clear an obstacle.

Once you have your list of angles have a local shop bend them up.