Project SR E30: Part 8 – Fabricating a Custom Stainless Steel Oval Exhaust
BMW E30 stainless oval exhaust fabrication
With the downpipe done, we move on to the next section. We now need to move the exhaust to the center of the car where it’s supposed to run. We sliced up our mandrel bends to mock up this shape.
BMW E30 Custom oval stainless exhaust fabrication
We mocked up the outlet angle and tacked the pieces together.

Let’s talk metal prep. When preparing our pipes for welding, there are two things we are concerned with: gap and contamination. Having a gap between pipes makes it harder to weld and weakens the joint. Stainless still is also very sensitive to contamination and has to be perfectly clean for a good weld.

Belt sanding exhaust pipe
One of the most useful tools for obtaining gap-less pipe joints is a belt sander. A belt sander is able to sand the end of the pipe perfectly flat, so it’s our first step in the metal preparation process.
Wire wheeling stainless steel before welding
Next we wire wheel the area around the joint to remove any oxidation or contaminants.
Deburring exhaust pipe before welding
Since we use a chop saw to cut our piping, it typically leaves a thick burr on the inside. Not only is it bad for exhaust flow but this burr is almost impossible to get clean, so it inherently introduces contaminants. We use a carbide burr on a die grinder to remove the burr.


    1. At the time, we couldn’t find any decent oval exhaust flanges that wouldn’t have taken away from the ground clearance.

      That being said, the exhaust is actually pretty easy to remove.

  1. Nice work, I was gonna see if you can check out the treehouse racing lollypops. they are smaller in physical size and gain more clearance. Your build reminds me of one of my friends who went KA-t in an e30 and it ran pretty gnar.

    Tip: might want to 2-piece the exhaust for when you need to change out the guibo, subframe bushings, and other rear maintenance.

    1. Yeah we’re definitely going to switch to a heim-style lolipop bushing down the line. I’ve gotten that burning polyurethane smell a couple of times already.

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