Half Pipes

Half Pipes

We’re about halfway done with this litany of 5-series exhaust setups, so the title seemed fitting. Plus we’re running out of pipe titles.

First, we are just about done with the E39 540i M-Sport rear section that we’re basing off our E39 M5 design. The resonators, tips and Y-pipe are all finalized and welded into place. Now, it’s up to us to fit it within the bumper at the proper position, so we can go ahead and start fabricating the mounts to connect to the new exhaust.


We’re also working towards the resonators from the existing setup, as well. We are utilizing the same clamp as we do in our E39 M5 Rear Section, but since the routing will be slightly different, we have to make the connecting pipe from scratch. Just like with our E39 M5 setup, the goal is to make the connecting arm as straight as possible, as every bend in the exhaust equates to a slight change in exhaust flow.


Over at the welding table, we’re about halfway done with the E39 M5 Rear Section, as well. Apparently, they’ve gone a bit gangbusters after the first UK customer picked his up and proceeded to shoot all sorts of video — free revving, driving under load, comparisons against similar exhausts, etc. So the jig sees more action than it does time in the closet, which is good. It also allows us to perfect the technique of creating this system by hand from scratch, cutting down on wasted time and increasing efficiency. While Tom is working on welding the 540i parts, Zak heads to the various saws in fabrication to get the metal cut to spec so that Tom can continue welding like the unwavering robot-human freak show that he is. We mean that in the nicest possible way.


As always, you can’t expect Fluid MotorUnion to mention the word “welding” without frothing at the mouth with excitement. And with all that mouth-frothing comes plenty of pictures, which we’re always willing to share with our dear readers. At this point, one of two Y-pipes are finished, and all the tips are in place, so we’re already nearing the home stretch. The tips and Y-pipes comprise the majority of the welding, with 4 welds on each tip (counting the weld between tip and resonator) and 5 on each Y-pipe (counting the two to the resonators), so most of the shots usually come from these two parts, and today’s no exception.


Random block of text to keep you on your toes!


And finally, on a non-welding note, we were trying to remove a fitting from a piece of braided stainless line, as the inside of the stainless line was dry rotted, but the fitting itself was perfectly fine. When using the acetylene torch to melt the old line off the fitting (as we’d already removed the braided stainless, and the underlying layer was basically cemented to this stupid fitting), the old line didn’t so much melt off as it did rapidly combust. A few stomps of a shoe put it out, and we recovered the fitting just fine, and since the camera was present at the time we figured we’d snap a picture.


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  • John Fredrickson
    Posted at 18:49h, 07 February

    I found your company through Alex’s channel, LegitStreetCars. Awesome work, you guys! This looks absolutely beautiful!! I want this on my ’03 540i M-Sport!

  • fluidmotorunion
    Posted at 09:11h, 08 February

    Thank you! Alex is a great guy we love collaborating with him. If you are looking for exhaust work or any other upgrades/maintenance feel free to shoot us an email at blog@fluidmotorunion.com

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