2G: Converting a GST exhaust to a GSX (exhaust fabrication)

[UofACATS]

I had a '95 GST that had piston exploding problems, so I bought a '95 GSX. I had a great exhaust on my GST, that being one Thermal R&D, and I realized I didn't want to buy another (of the exact same) exhaust system.

Time to cut up the GST exhaust and re-weld to fit the GSX.

First I borrowed a chop saw and bought a metal cutting wheel. Then I got out the safety goggles and ear protection. I cut the pieces as long as I could, trying to salvage every piece and bend. Then I de-burred those pieces quickly with a dremel-style grinder.

The exhaust system had to serve multiple functions, all being critical.
1. it has to sound good. I reused the Thermal muffler, so I'm good there.
2. It has to flow well. I'm using three inch piping with minimal bends. Check.
3. It has to allow for the use of a of a "test pipe" for track days but also a high-flow cat because it must pass emissions. I have a high-flow cat and a straight-through perforated-core resonator that are the exact same dimensions, and can be swapped via exhaust clamps. I'm good there.

Let's get started.

First up, test the fit of a GST muffler on a GSX. Fits great. Good start.

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Start cutting the GST exhaust into pieces.

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Here are the two interchangeable pieces, one for the track, one for the emissions station.

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Both will be held on, and changed relatively easily via these clamps. In hindsight, these are not the greatest clamps because they leak a little, but for the price they work fine. V-Band is what I recommend if you can swing it.

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[UofACATS]

Part of this thread is to show the process one often goes through when learning as you go. There is often a learning curve, and you'll see that here. You'll see my method of MIG welding on thin material, and I'll show you some shortcomings.

The welder is a Lincoln 180C. It's powered by 220, thus I work outside where it's windy and hot/cold, and not in my garage where there's only 110.

The chop saw does just fine when it comes to straight cuts.

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Here's the first piece getting prepped. At the start of this project, I severely underestimated the importance of prepping the metal to be welded. It's very important.

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Here's the first bend. You see my rudimentary methods. Basically I cut/trimmed the bend until I liked what I saw. Then I tacked into place, pulled the pieces, then welded. I tried to take my time, welding partial ares at a time to minimize distortion. Luckily, with a project like this, absolute precision is not necessary. If you do happen to weld something incorrectly you can always cut that part out and try again. Just keep an eye on available material.

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It was nighttime by the time I took this, sorry it's a bad picture. You can see it taking the basic shape however.

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[UofACATS]

Test fitting another piece here. Getting exhaust pieces to line up and fit well is harder than you would think. I re-cut most pieces more than once, and that's after I measured and marked before cutting.

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Here's a couple straight pieces after prep and tack weld. It's important to get as tight a fit as possible. It makes welding the two together that much easier. I also put this in here so you could see I used a brief section of an old MR downpipe, (the portion that says Megan Racing on it) so it's not 100% Thermal R&D piping. I had leftover exhaust piping however, so you should be able to duplicate this without any additional piping. This is however based on the fact that my downpipe is a "cat eliminator" and thus is very long. With the addition of the cat or resonator, that leaves little length of piping actually needed. Further pictures will make this clearer.

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Welded. Here you see I learned to pulse weld on thinner material. It's my method in order to help prevent burn through while still getting good penetration and strength.

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Here is a picture from inside the pipe. You can see some welding error here. The blobs of metal are obviously too far apart. This is one downside to the method I use. The welds should be closer together to form a continuous bead. If strength was necessary here, this would be scrapped and redone. It's an exhaust pipe however, so it goes on. It's been fine for awhile now, I'll continue to look at it when the car is on stands. (Which is frequent.)

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[UofACATS]

You can see here while fitment is not absolutely perfect, it's pretty good. Try to get the pieces as tight as possible. I like grinding down the tack as well so it interferes less as I go over it with the bead.

Take the wire wheel to the pipe to clean it up.

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Here's another error picture. I was using some non-ss wire in the machine! It actually cleaned up real purdy after I hit it with the wire wheel, but I'm not about to polish my exhaust system.

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At this time, I was ready to look at the hangers. I contemplated a bit, then went out to my stock exhaust and cut off all the hangers. Then did the same for all the random exhausts I had laying around. (You can tell I can't remember where this hanger came from ) Then I held them in place and used my imagination. I came up with this very simple design, since I loathe trying to remove the exhaust from a stubborn hanger with a huge lip on it. This one holds well and is easy to work with too. Perfect.

You can see the angle of the hanger in the picture. I maintained that angle while welding. This required the exhaust pipe to come up and meet the rubber hanger. This is so it's tight with no rattling, and maximum ground clearance.

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[UofACATS]

Here's a completed picture minus the hangers Pretty simple.

 

[UofACATS]

So, what does it sound like?

Idle clip here:
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So, what does the 4500 two-step sound like too late at night my neighbors love me?

Clip here:

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