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2010 2011 BMW 5 Series Forum F10 F10 Technical Topics DIY Guides & Discussions Exhaust Mod (M5 or Megan M5) DIY
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      07-11-2016, 10:55 AM   #1
krautmeister
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Exhaust Mod (M5 or Megan M5) DIY

Ok, had this posted in another thread to further the topic, but figured a good DIY would be in order. I wondered and wondered about how the design would fit and not leave it up to any muffler shop to bend piping at will and chop up the nice stock exhaust.

I'm well aware of the tremendous amount of information that is free on these types of forums so I always like to pay it forward when possible.

So here is a quick guide, not a detailed step by step as I'm not a welding master either. This is for a 550i, but the pipe layout should be similar to other dual exhaust set ups (obviously 550i being 2.75" OD, 535i being 2.5" OD pipes).


Tool/ Supply List:

(1) Megan M5 "axle back" exhaust: These are around $580 on the inter webs... also, axle back is a loose term as they are just mufflers with hangers.

(2) Mandrel Bent "U" bends in 3" OD, 4" radius bends of aluminized steel: I bought from an outfit called Columbia River Mandrel Bending. I also was limited in using aluminized steel due to the 90AMP welder. Stainless steel is available as well, but requires a better MIG welder. http://www.mandrelbends.com

(1) 90 AMP MIG Welder (I am limited by 120v): I bought from Harbor Freight cheap... they run under $100 during sales. HB 90 AMP Mig Welder

(1) Exhaust pipe cutter: either you can use a reciprocating saw with a metal blade or get an exhaust pipe cutter. Mine was this: GearWrench 2031DD Exhaust and Tailpipe Cutter

(1) Bench sander / grinder: it is easier to clean up pipe sections this way. You can use a hand held or bench top.

PREPARE THE TEMPLATE:

Here is my design that I overlaid the F10 exhaust in Photoshop and mocked in the Megan exhaust. I painstakingly made the image as perfectly square as possible as well as scaling of the mufflers. Then it was imported into CAD to get the exact pipe construction.



Even if you stop here and do not do the work, it will be easier to convince a muffler shop to do this with mandrel bent sections as its quite aggressive bends (OEM pops out at 45 degrees for this reason). Use the PDF attached, print and take that as the plans.

If you would like, I'd suggest to cut out a full scale section of the pipe on cardboard and overlay it onto your pipe to get an idea of the layout prior to cutting.



PDF TEMPLATE

FAB THE S-PIPE:

Cut the mandrel bent sections by laying them over the template and mark the radius bends with tape. Make sure that you are marking the cuts accurately from tangent to tangent.

If you follow these directions, using the parts, you should only need the 2 U bent pipes at 1 per side and harvest the bent sections and straight sections to make up the S-pipe.









Yes the welds are terrible. I would suggest that if you do not go the welding route, that you take the template and cut pipe sections or any combination of your labor and have the shop complete it. I attempted to weld the entire pipe, but I should have just left it tacked for the shop to complete.

The end that goes into the muffler will have to be swaged to 3.25" OD to fit inside the Megan M5 muffler of 3.25" ID. I tried the cheap DIY pipe expanders and its easier just to get a shop to do it or buy the expensive one!

The end that goes into the mid pipe will have to be either used with a reducer from 3" OD to 2.75" OD to mate up to the stock piping. You may have to play with the length of that section from the final bend pending where you cut it and how your piping lines up if you want to band clamp the pipe.

I ended up having a shop just swage the stock pipe and welding my S-pipe on both ends.

This is what it looks like mocked up:



CUT THE MID PIPE:

Cut about here, behind the brace (towards the rear). Leave enough of the bend available so that your stock pipe can be welded easily or clamped if you choose to go back to stock.

Make sure your shop knows where you want it cut if you take it there. They will want to cut at the bend, but leave some straight section as it will be better for clamping or welding later.

This image is for illustration purposes. All of this can be done on the car, with ramps.



FINAL NOTES:

The hangers will have to be played around with quite a bit. I had a shop do the rest so that it could be rock solid, but the S-Pipe sped up the time as well as controlling the aesthetics and bends.

These directions were for a 550i M-Sport diffuser so for a OEM M5 diffuser, the pipes may have to be adjusted. I believe you could rotate the S-Pipe enough to bring the tip locations in 1" or so more to center. This would also raise the tip location, but I believe that the M5 diffuser tucks the exhaust up higher.

The final result:



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      07-11-2016, 02:07 PM   #2
lsturbointeg
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what if you just make them and sell the pipe...i would seriously pay you for it! cause it looks like you took your time and made sure the bends were smooth! a muffler shop would just do a Mickey Mouse job and call it a day!
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~LedermanzWheel|ShadowlinKit|CarbonGrills|MSportRe arBumper||Meisterschaft90mmQuadExhaust~
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      07-11-2016, 03:28 PM   #3
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Man.. I'd probably help you out for free except for materials, but these days with a baby... time is just not in abundance!

ETA... you can see my fence needs pressure washing, fixing, driveway needs weeded, washing... and what do I do? I mod my car of course!

Last edited by krautmeister; 07-11-2016 at 04:16 PM.
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      07-11-2016, 03:43 PM   #4
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F10 550i Megan M5 Exhaust Rev

F10 550i Megan M5 Exhaust Start
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      07-12-2016, 12:00 PM   #5
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Quote:
Originally Posted by krautmeister View Post


i have the Meisterschaft's from a 550 i still have yet to put on but because of my M5 DTM diffuser it will have to modified just like yours to make it work. pretty much the modification is just the pipe bends like what you did
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~LedermanzWheel|ShadowlinKit|CarbonGrills|MSportRe arBumper||Meisterschaft90mmQuadExhaust~
~KWV1Coilovers|WstyleRoofSpoiler|CarbonRearSplitte r~35% TinT~
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      02-28-2017, 09:16 PM   #6
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now. 214-732-8207
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