This was done on a 1.8t gti, but the same procedure, materials and concepts will work on just about any car you've got.
Alright, so I wanted to ditch my dump valve on the stock exhaust and go with something less loud and more free flowing. Not wanting to shell out $700+ for a full TB system, I decided to give doing it myself a try. 5 hours after I jacked the car up, I had a full turboback system installed.
First thing's first, gather parts and tools. Here's what I used:
- Assorted wrenches and sockets. Mainly 17mm for the turbo stud nuts.
- Chop saw
- Angle grinder
- MIG welder (I use a hobart handler w/ C25 shielding gas)
If you don't have it and can't borrow it, buy it. I can always find an excuse to buy tools, and never feel guilty doing it.
- 3" eBay Downpipe ($103)
- 2.5" x 4ft steel tubing from summit ($11, I bought two and only touched one)
- two 2.5" u-bends from summit. I went with the 3" radius. ($50)
- cheap muffler from napa, flow-tech raptor ($25)
- two 3-bolt 2.5" exhaust flanges ($10)
- 3ft of 3/8" steel rod for hangers ($3)
- assorted nuts and bolts
As far as the muffler goes, I'll explain. I wanted to do some experimenting with resonator/muffler combos but didn't have the time right now. So, to spare my ears, and those of my neighbors, I threw a cheapo muffler on from napa to get-r-done for now.
Alright, here we go. The basic idea is that we use the eBay downpipe and it's reducer section. We mate that with bits and pieces of the steel from summit and we've got a cheap turboback exhaust. I won't go over how to jack up your car. If you can't do that safely, you probably shouldnt try this.
Step 1: First, get the stock exhaust and downpipe off. This seems to be trouble for some, so here's how I've gathered it's best to remove the nuts on the downpipe. The issue is that if the nuts are seized onto the studs and you crank on them, you'll break a turbo stud. Not fun. Here's what I did. Went out during lunch break at work and soaked the nuts with PB Blaster. Then when I got home to start the install, I soaked 'em again (from the bottom this time). Wait about 30min, and get under there. Mine were 17mm. You're gonna need a socket wrench with a deep well 17mm socket, or an open ended wrench. I used a bit of both. Slow and steady does it. If the nut gets stuck somewhere, tighten it back up a 1/2 turn and soak it with PB Blaster again.
Once you've got that off, the hard part is done. Use the sawzall to cut off the rear end of the exhaust, right before it goes over the axle. Then, without having to mess around with the sleeve clamp, undo the 8 nuts on the subframe/exhaust support and drop that. Careful, because that's the only thing left holding the exhaust on and keep an eye on the o2 sensors. Take them off once you've got it sitting on the ground. I put a jackstand under the cat, to help lower it in a controlled manner. You can see that I tried to cut off the clamps (they were too rusted) then decided I could skip that step all together.
Pull out the stock muffler too. You'll have to yank it out of the hangers, no biggie.
The obligatory comparison pic:
Step 2: Throw the new DP on. This is really easy. Slide it in there and bolt'er back up. I've heard 30 ft-lbs, so that's what I did, who knows. Make sure you use a new gasket when you put the new DP on. (or don't, who really cares) We'll discus o2 sensor options later, just leave em.
Now comes the fun part.
Step 3: Start fitting the new tubing. The reducer that came with the DP had a step for 2.5" exhaust and a step for 2.25" (i think). I hacked off the 2.25" section, leaving a 2.5" pipe for me to work with. Now, use a tape measure to mock up what you want your first straight piece to be. After my cut on the DP reducer, I ended up wanting 27". Hold one of your u-bends up to the first bend and estimate. (I'll note that if you utilize the straight ends of the u-bend in this calculation, you're welding a straight seam instead of one mid-bend)
Cut that piece of tubing and clean up the ends with a grinder and some sand paper. I gues I should talk about how I went about the welding. Having no previous fabrication experience really, I just did what made sense to me. I tacked everything in place and at the very end, when I was happy with it, I took it all off and welded the seams.
So, tack weld that new piece of straight pipe onto your reducer. I chose to take the reducer off and tack weld it on my garage floor, so I could be sure to get it straight. Don't worry if when you put it back in it sags, the subframe/exhaust support will take care of that, it's just the flex section doing it's job.
Step 4: Repeat. This is where it's up to you to make good decisions and measure twice. Remember, measure twice, cut once. Having to cut twice wastes time and material. If you're unsure of your ability to do this carefully, consider ordering three u-bends. Here you can see pretty much what I did. It's important that when cutting tubing with the chop saw mid-bend, that you concentrate on getting a 'true' circle and not an oval. This will greatly reduce the amount of time you spend welding.
In this section is where you should put the flanges. I don't know if this is common practice, but it seemed to me like it would make it a lot easier to put in and out. Bolt them together first, and work with them as one piece.
Step 5: Muffler. Once you get near the end, you'll be ready for another straight section to connect to your muffler. Hold the muffler up to where you want it and use your tape measure to see how long of a piece you want. This piece will probably need to have an exhaust hanger on it. Use the 3/8in rod and bend it (figure it out, I just put it under a 2x4 and bet it up) then cut it to the length you want. Remember that the added weight of the muffler will make it stretch the rubber mount a little bit.
I'll add some pictures of this tomorrow.
Hold off on welding the muffler in until the very end. It really isn't necessary, and will only stress your tack welds and make things harder to move around
Step 6: Weld. Take everything off and weld it up. I won't go over how to do this, as I'm sure there are better welding sources than myself readily available. I will say that obviously the better the pieces fit together, the easier your life will be. My welds weren't the greatest ecause my cylinder is running pretty low (that's my theory anyway). They do the job just fine though.
So you're basically done. Bolt the two pieces back on and bolt the subframe back on. I chose to bend the exhaust hanger in the subframe to better accomodate the larger 2.5in tubing. Do what you want
Step 7: Finish up. At this point, everything is taken care of but the muffler and o2 sensors. As far as the muffler goes, I mounted it such that the outlet was just below the rear exhaust hanger. I welded another piece of 3/8in rod the the back end of the muffler and called it a day. I then slipped the 2.5in tubing now bolted to the car into the inlet of the muffler and positioned it how I wanted before running a bead as far as I could around the seam. You could take the read section off again and weld the seam, but it was getting late, so I was able to get all but about an inch welded up. It was a tight fit, so I'm not worried about leaks.
You can decide what to do about tips, I went with hidden.
The o2 sensor issue can be solved a few different ways, as far as I've read. Some chip tuners offer a file that gets rid of the CEL caused by not having a cat. I believe APR is one of them. Another option is to use spark plug non-foulers to space the rear o2 sensor. Here's the original link:
It should be fairly obvious which o2 sensor was in front and which was in back. It's the rear one that's an issue. The DP that I ended up with happened to have the sensor bung in a decent location, others have to use a hammer to dent the heatshield to make it fit.
Step 8: Enjoy. Simple as that.
Yea, not everyone has a MIG welder, but for the cost of some name brand TB systems, you can buy yourself the components to your own custom system and the tools you'll need! (some of them anyway)
As always, do this at your own risk. It's not my fault if you hurt yourself, or if you don't like what you end up making. One thing I ran into is that a few of the bolts on my flanges loosened up and were making a god-awful rattling noise. A little loctite should take care of that. You exhaust gurus, please feel free to add in whatever advice or input you have. Like I said, I really know nothing about exhaust fabrication.
Sound tone and level is determined by the muffler/resonator combination you choose to go with. This is a $20 muffler that I used just to keep initial cost down. It's since been replaced, and sounds completely different.