Build Log: M57 X5


Nov 7, 2016
San Diego
And a 200 shot of nos or whatever. Upgraded turbos do not even make that much.

That sounds bad ass. What would you say 25% louder?

This what you used?
Correct, 3" QTP but I added the turn-down tip and replaced the HUGE momentary switch with a much sleeker and easier to operate switch.

Hard to say about the audible change since from my perspective the turn-down under the car (when open) makes it seem much louder in the cabin than it would be as a rear exiting exhaust. Conversely in the video behind the X5 the exhaust through the muffler may seem louder as it's pointed reward and the turndown in pointed down. I like having the option with the valve but in an ideal world both open and closed would exit the rear of the X5 but the added time/labor/expense to do this isn't worth it IMO.


Nov 7, 2016
San Diego
I had a chance to execute the 3.15 rear end swap, I will be making a separate thread on this but will add some cliff notes here. For those who have done diff swaps, the change from 3.64 to 3.15 doesn't offer any surprises. Install was straight forward. The downside is acceleration from a dig isn't as dramatic but normal daily driving benefits from the gearing as the X5 has a lot of torque and has no issue moving itself along. The real benefit of this comes at highway speeds, I did some stretches at 60-65mph and it was returning ~35mpg which is what the 3.64 mustered. 65-80mph is where the 3.64 would fall apart and MPGs would drop down to the low-mid 20s, with the 3.15 at 70mph the X5 was still returning 35mpg. I still need to do some testing at higher highway speeds, 80+mph, but the X5 is definitely not as affected by the added speed. I will be swapping in the front diff to complete the gearing conversion and recommend this mod to others who value highway MPG and a less dramatic driving experience overall.

I was able to get a drive from San Diego up to Orange County, just under a 200 mile round trip, mainly flat with some rolling hills. On the drive up I was able to get 32.2mpg and this included 10 miles of urban driving to a shop. On the way home I got 35.1mpg highway only. Unfortunately I wasn't able to hand calculate the figures, this is based off cluster read-out and mine is usually 0-1mpg optimistic so take it for what it's worth.



Big Ass Wrench

If you recall I was playing around with running the shorter rear-air struts with the taller (2" taller) upper strut mounts from a non-air X5 and the goal was to get proper strut actuation while lowered. the air strut with the air mount was too compressed and the air strut with the non-air mount was too extended so I made some 1/2" and 3/4" spacers out of plastic cutting boards which are used to space the taller non-air mount down bring the strut into normal operating range.

To accommodate the spacers I needed to replace the OEM M10 studs with longer versions, after some research I found that ATVs run M10 wheels studs and with all the crazy modding that is going on in that industry, some companies make extended wheel studs to accommodate spacers. I found some that gave me an extra ~20mm of usable thread length.

Old studs out

Extended studs

Building spacers

I made 2 sets of 1/2" and a pair of 3/4" so I can space the mounts as needed between 1/2-1"

What's interesting is how little stanchion travel BMW allows before the bump stops come into play on the rear struts. There are 3 OEM bump stop options: short, medium, and long with the short being sport, long being for 3rd row, and medium for X5s spec's in the middle.
Looking at the meidum bump stop install you can see there is only about 10mm of travel before the bump stop is activated, this is why most X5s ride so poorly when lowered, most are riding on the bump stops, literally.

Here is the medium BS in the back and the sport (short) bump stop installed.

Here is a sport trimmed.

I installed the medium bump stop and paired with a 1/2" spacer which positions the strut in an acceptable operating range but closer to the "extended" side of the spectrum as opposed to "compressed." I know I am still mis-matching the dampening characteristics of the strut with squished air bags but this is a step in the right direction, more testing to do.

I got around to installing the switch for my QTP exhaust valve. I ditched the huge/ugly/hard-to-operate switch QTP supplies for a sleeker momentary switch I bought off eBay, I wanted a more OEM look and easier operation. The goal was to mount the switch in an easy to access location that was also a bit out of sight, and I wanted to mount the switch into a panel or piece of trim that could be easily replaced if I wanted to revert back to stock. Very happy with how everything came together.


With the dark theme of the X5 the taillights and their bright red bothered me a bit so I got some Lamin-X smoked film. This is the lightest they make and offers the "dark-cherry" look I was going for. I also used some knifeless tape to cut the film so that it was only on the red and the white/clear sections have no film.

As a lighting nerd this is a step in the wrong direction in terms of illumination and safety so I had to offset that. I upgraded the rear turn signal and brake light bulbs to Diode Dynamics LED bulbs, I also coded the light module to do a double hazard flash. The bulbs are significantly brighter and combined with the instant-on flash of LEDs the turn signal more effective now than it was in the OEM configuration, even with the tint.



Nov 7, 2016
San Diego
I was able to get the X5 on some dynos, both a Mustang Dyno and a Dynojet.

Mustang was 317whp 504wtq
Dynojet was 370whp 520wtq

For those that don't know Mustang dynos use load and typically read lower. In general Mustang dynos should be more accurate but it's hard to say since it all comes down to proper calibration. Dynojets are more common for "big stick" comparisons amongst enthusiasts as dynojets are simply and measure power based off how quickly the vehicle can spin a drum, less variables to manipulate the numbers.

The dynojet operator was starting the pulls at way higher RPMs then he should have, shame on me for not picking up on this but he was going WOT between 2,500 and 3,000 rpm (seriously) and the M57 makes peak TQ around 2,950 so for my observant BMW diesel enthusiasts you may notice the Dynojet TQ numbers seem low, this is why, with a clean pull TQ #s would likely be ~550wtq.

On the Mustang dyno I was able to compare my custom inlet to the OEM airbox and although the data isn't perfect since the engine was getting a little heat soaked, it looks like the intake does flow better and offered more power, roughly +10hp +10tq. I am patiently waiting for the shop to email me the overlaid graphs.

On the Dynojet I did 2 pulls with my custom intake and 2 with just a 3.5" velocity stack mounted on the MAF. The pulls are so chaotic and the data so sloppy it's hard to discern what's going on but there was no measurable difference between the two.

Mustang session

Dynojet session

Custom Intake

Velocity stack
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Reactions: derekgates and Torgus


Feb 23, 2018
Your motivation and creative work-arounds to problems continues to amaze me.

I knew I wanted an E91 but never knew I wanted an X5 until seeing your posts. I'm loving the diff changes and observations of mpg; I am about to do the reverse with my 335is (2.56->3.15) :D


Nov 7, 2016
San Diego
ZL1 wheels repaired and powder coated Prismatic "Graphite Black" it's essentially a black with a fine metallic flake and a satin finish. I liked the way the OEM GM satin black finish looked so I used that as a base and I figured the slight metallic finish of the graphite black would compliment the Platinum Grey Metallic on the body. The powder coat turned out to be slightly different than I was envisioning but overall I am very happy.

With my front left sidewall damaged and the other tires on lower tread it was time to replace the tires. I jumped from a 295/40/20 square setup of Pirelli Scorpion Verde to a slightly taller set of Hankook Ventus ST RH06 in 295/45/20. I knew they would be tight and after much research, measuring, and guesstimating I still wasn't confident they would fit. I was relieved to find out the fit perfectly.

I was going between these Hankook RH06s in 295/45 or doing the Michelin Pilot 4 SUV in 305/40. I run Hankook Evos on all my other cars and appreciate the value the tires offer; good grip, quiet ride, adequate tread life, and a fair price. My personal experience combined with the reviews I read were enough for me to give the tires a shot. The Hankooks are about 1/3 the price as the Michelins too.

For the way I use my X5 this 295/45 20x11 square setup is perfect. Given the limitations of the vehicle, tire options, DXC, etc. I can't think of anything I would change. Jumping back up to a taller and heavier tire does zap some of the acceleration performance but the added comfort of the beefy tires is welcomed and worth the trade off.

I am glad the X5 is back from my wheel guy but it was REAL fun dailying the E61 again, never a dull moment.

Garage space was taken by my e39 touring which is getting engine work and a manual swap so I had to get creative in the drive way with 2 jack stands and removing 2 wheels at a time to swap tires. lol





No rubbing except at full-lock to the right. I will heat, melt, mold this vent further forward. It eats up a lot of space but I can work with it.

I love tight fitment. Looking at the X5 from afar it looks fairly normal but poke your head in the wheel well and you can see where all the research, calculations ....and luck paid off! lol


A look at the tread pattern.

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