Build Log: M57 X5

TwinTurboWagon

Corporal
Nov 7, 2016
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San Diego
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Torgus

Colonel
Nov 6, 2016
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Thanks!

Did you have to drill that hole or is it there on both sides?

Looking back would you have done anything differently?
 

TwinTurboWagon

Corporal
Nov 7, 2016
192
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San Diego
As my age gets higher so does my ride height :) Front KWs were raised to match the rear and ditch the rake for a level ride height, very happy with the the results. I am still developing thoughts on the KWs so for those interested in feedback please sit tight.

I am happy to report the exhaust system is complete. Installing the larger (wider) F85 rear differential meant the stock piping wouldn't fit and for the a while I ran some clamps, a resonator, and a turn down off my mid pipe which terminated just before the diff. I was toying with reinstalling my QTP exhaust valve as I appreciated having the option to open the valve when I wanted to puff my M57 chest but the reality is space was now a premium and although my QTP valve has been reliable, in general they are not known for being particularly so. I again, took the mature/classy/boring? route and decided to keep the exhaust quiet by skipping the valve, keeping the OEM muffler, and also adding a Vibrant Ultra Quiet Resonator.

I was surprised to learn the resonator killed a lot of the turbo spool. I run the same resonator on my E61 with twin turbos and the spool is loud and piercing, not on the M57 I guess those frequencies were gobbled up. The resonator also kept the hissing and fluttery noises to a minimum which I do appreciate as the growl of the M57 comes through better. Overall the sound of the system is subtle, a bit classier/cleaner, but still has character.

I had a local shop assist with the fabrication. They welded the Vibrant resonator into my Rawtek mid pipe, fabricated piping around the rear differential to connect mid pipe to OEM muffler, and fabricated piping from the muffler to accommodate the rear tips. A couple v bands were added to make the system modular and easier to install/remove.
Everything is mandrel bent and tig welded.

Here is the layout of the system:
Rawtek down-pipe
Rawtek catted mid-pipe w/ Vibrant ultra quiet resonator
OEM E70 X5D muffler w/ OEM F15 M Sport tips

Sorry for the shit pics but you get the idea...
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Fitting F15 tips isn't for the faint of heart, it requires precise trimming and some creative fabrication skills to bring it all together. After mocking up the tips, eyeing, and measuring multiple times I was convinced it could work and proceeded to prep and trim the bumper. I traced the tip onto cardboard and then used a torx bit to extend the size, my goal was to have ~1/4" clearance around the tip, erroring on the side of "tight" and clearancing more as needed. Nothing is worse than having a hacked up bumper with excessively large holes. yuk
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I applied tape to the bumper and used both the actual F15 tip and template to scribble my cut mark, double, triple, and quadruple checking as I went.
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The driver side came out in about 20 pieces and I was a lot more proficient on the passenger side, here is the rough cut of the first pass, I came back in to clean up everything
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Unibody was also slightly trimmed
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Little OEM tip swimming in a sea of clearance.
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Initial pics after installation.
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Scratches on the bumper courtesy of the fabrication shop. Aside from this collateral damage I was very happy with their work. As you can see the bumper needed some additional clearance.
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Added tape and revised my trimming.
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Muffler/bumper fitment is so tight the bumper needs to be removed to remove muffler, not ideal but sometimes I sacrifice function for aesthetics, this is one of those times. V-band just before muffler makes this process much easier.
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I thought about painting the muffler black to match the tips but it would have been a bit of work and I wasn't convinced it wouldn't chip over time from road debris so I decided just to refurbish the muffler and piping with some wet sanding, I love how you can bring new life to metal with some elbow grease.
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Cleaned, scuffed, and primed.
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....and painted
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Final pics
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fmorelli

Lieutenant General
Staff member
Aug 11, 2017
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Virginia
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E89 Z4 35i, F10 535d
Nice work as usual, @TwinTurboWagon. Evan, can I asked (maybe I missed it) why you stuck with the rear muffler? I would understand you want the X5 quiet, but I have to imagine between turbos, cat and mid-pipe muffler that there is not much left to quiet down. Especially going down the highway.
 

TwinTurboWagon

Corporal
Nov 7, 2016
192
211
0
San Diego
Nice work as usual, @TwinTurboWagon. Evan, can I asked (maybe I missed it) why you stuck with the rear muffler? I would understand you want the X5 quiet, but I have to imagine between turbos, cat and mid-pipe muffler that there is not much left to quiet down. Especially going down the highway.
I did want the X5 quiet-ish. I was going to have a custom muffler delete fabricated with twin Vibrant UQRs but decided to put one in the mid pipe and just reuse the muffler for simplicity and to keep the cost down on fabrication. When I was temporarily running the exhaust with the turn-down at the rear axle with the DOC and Vibrant resonator upstream it was much louder than I expected, I think some of this was due to having a turn down firing exhaust gasses at the ground which would resonate under the car instead of fire backwards but still. The X5 still has some character with the exhaust and paired with my turbo inlet you still get enjoyable sounds coming from both ends of the vehicle, it appeases my "I want to hear what's going on with the engine" but not to the point where it's annoying to me (or my wife).
 
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TwinTurboWagon

Corporal
Nov 7, 2016
192
211
0
San Diego
Mini update.

The big news is this San Diego, CA vehicle is now a Boulder, CO vehicle as I have recently moved. The 1,000+ mile drive through CA, AZ, NV, UT, and CO was awesome and the X5 was a champ. Loaded to the gills with tools, belongings, bikes etc. it returned 22-23mpg on the drive which may not seem that great but with speeds between 80-90mph and elevation eclipsing 11,000ft through the rockies, they are satisfactory numbers. For reference the wife's Q7 4M with a few suitcases and 2 dogs, no cargo box or aero drag, only mustered 19mpg.

Also, now that I live in a fairly flat area the X5 is poised for MPG greatness. I am 1/2 way through my first tank of fuel in Boulder with mostly urban driving checking out homes for sale and I am sitting at 28+mpg which includes some spirited canyon driving and overtaking. By my calculations ~30mpg for a tank of fuel should be the new norm. Impressive considering the altitude and the fact I would get 21-24mpg per tank in CA.

Here are a couple better pics of my exhaust system as well as the "cool" X5M trans pan and differential heat sinks.
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Apparently the X5 with the KWs installed couldn't get aligned on the Hunter machines? Techs say that the machine needs to have weight added to the back of the vehicle to read specs and they weren't able to do this. Kind of a bummer since I paid for a lifetime alignment via Firestone and essentially it's now useless.
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Fresh oil change for the drive out to CO and knowing I won't have my tools available for the first few months out here.
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Some pics on the drive East
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