X5M Electronic LSD and Dynamic Performance Control Retrofit

[ucsbwsr]

I mostly post in my build log but I think this warrants it's own thread.

Let's start with some background info, motivation, and goals.

The M57 diesel engine is unique in it's ability to pair high performance with efficiency and reliability. The goal with my X5 was always to create a vehicle that offers X5M performance but without all the M engine issues. In other words, build X5M or Trackhawk killer that's reliable and gets 30+mpg

Currently, my X5D makes ~370whp and ~530wtq and once I get my hybrid turbo back from Tim and install fueling upgrades those numbers will be going up to 400+whp and 600+wtq. In other words; roughly the same HP as a stock E70 X5M with an additional +200wtq. Sounds fun but power is useless without control and destroying CV axles is no fun so I have decided to explore retrofitting an electronic LSD from an X5M, mainly for the added durability and piece of mind but the added grip/dynamics are a bonus.

Regarding the M57 engine, for those who are unfamiliar it's a 3.0L inline 6 diesel engine that has was in service for over a decade, mainly in Europe in the form of iron blocks with single turbos. It's a bit of an indestructible workhorse.

The US got the latest/greatest version of it in the E90 335d and E70 X5d which is aluminum block with twin compound turbos. Thankfully for the M57 community the diesel truck tuner Santjer Performance has taken an interest in the platform. He has developed and is currently testing a dual HPFP setup and a Triple Turbo kit which is producing numbers in the realm of 700+whp and 1,000+wtq on the stock engine. Impressive when you think about the number of engines which can make 4-digit power without needing to be opened up and built.

The point is the M57 makes good power with "basic" mods/tuning and has potential to be a real monster when pushed. 335Ds run into traction issues where the X5 has AWD, huge tires, and a 5,000lb curb weight so it hooks up a lot more but that torque is really going to stress the drivetrain. Enter this project....


For those who want to learn more about the technical details of the electronic LSD and the Dynamic Performance Control system here is a link to literature:
https://archive.org/details/BMWTechn...cs_WB/mode/1up


For those that want the cliff notes..... Dynamic Performance Control (DPC) an integration of systems where computers take the data from various sensors and driver inputs to control the "active" systems of the vehicle to further improve chassis dynamics, stability, and performance.

At the heart of this system is the Integrated Chassis Management (ICM) which is a module that acts like a hub and the main brain connecting the various systems. Currently on my X5 I don't have any active systems with the exception of I suppose the rear air which is load-leveling but when I install the ICM module it will communicate with the other CANBUS systems and receive inputs from my steering column (wheel angle), throttle position, brake pedal position, wheel speed sensors, as well as longitudinal/lateral acceleration, and yaw rate. Based off this data the ICM can understand what the vehicle is doing and likely what situation I am in as a driver; braking, cornering, etc.

Here is a diagram on how the system will communicate once installed. #1 #6 and #7 are what I am adding


If the X5 is equipped with them there are additional systems such as servotronic steering, active sway bars, active steering, and active shocks which also integrated and part of this Dynamic Performance Control system. Personally I am not interested in those other systems and I am happy to report it looks like I can retrofit the electronic differential as an a la carte system. Nice.

HOW THE DIFFERNTIAL FUNCTIONS
You can break the differential down into 3 sections. In the middle is a traditional, albeit strong, open differential and on either side is are clutch packs which are controlled (engaged/disengaged) by electronic motors. Just like the x-drive AWD system controls the power between the front and rear wheels, the active differential takes it a step further and controls the torque between the rear wheels. Fun fact, BMW states the differential can transfer 1,800nm (1,325 ft/lb) of torque from one wheel to the other while under load. The differential is active pretty much all the time; while under load, while coasting, and during over-run.


Here is a short video

A more detailed video

BENEFITS
Increased stability and agility. The easiest way to think about this is in a scenario where you are taking a corner, let's say turning left at speed. A traditional locking or limited slip differential would send power from a wheel that slips to the other wheel with grip or splits the power evenly to both rear wheels. in the scenario of this left hand corner the electronic differential will send more torque to the right rear wheel which will help the vehicle rotate around the axis of the corner with less steering input and more grip. This differential knows what you are doing and helps you increase speed and stability. Traditional diffs are relatively "dumb" in that they only know what the rear wheels are doing in relation to each other and nothing else. An LSD plays tug of war sending the torque L/R as wheels spin-n-grip, the electronic differential has a lot more finesse with a precise distribution the the torque that not only helps grip but helps you carry speed and pace in different scenarios.


THE PROJECT
Buy the parts, Install, Wire, Code, and DONE! Ha! In theory it's very simple but I am sure there will be some challenges.

The parts needed
1. Electronic Differential: I have previously swapped from the stock 3.64 diffs that came with the diesel to the 3.15 diffs that came on the 35i and 50i X5s. MAKE SURE YOUR F?R DIFFS HAVE THE SAME RATIO or kiss your transfer case goodbye. The E70 X5M has a 3.91, both E71 X6 and F85 X5M have 3.15 ratios, nice. The diffs are identical with the exception of the F85 having larger diameter output flanges to accommodate beefier axles, F85 diffs also seem to carry a HUGE price premium. I wanted the beefier output shafts so I sourced an E71 diff and will swap the output flanges and viola! I know have an F85 diff for a fraction of the cost.
2. Axles: X5s have splines based half shafts and the electronic diffs have the inner CV bolt to the differential so you will need bolt-mounted axles.
3. QMVH Module: This is the module which controls the motors in the differential, it also monitors electric motor position, Electric motor temp, as well as the gear oil temp in the diff and sends that info back to the ICM module.
ICM Module: The brain that makes Dynamic Performance Control possible, it controls the QMVH module which controls the diff.
4. QMVH-Diff wiring harness: With all the electric motors and sensors the diff has 6 electrical connections, this harness connects the diff to the ICM module and also the Powertrain CAN BUS (PT-CAN) which includes DSC, DME/DDE, Transfer Case, and Junction Box.
5. Additional Wiring: This is a tricky one as it looks like the connections for the ICM and QMVH module are part of the main harness. I came to this conclusion as I was unable to find any harnesses listed in RealOEM and I see some dismantlers removing the modules with wiring pigtails attached which suggests main harness.

As you can see I have all items minus wiring. The QMVH harness is in transit from the UK and I am patiently waiting for a local dismantler to part out an E70 X5M so I can hopefully get the pigtails I need for each module.

PRICE
Heavily dependent on your ability to source deals. So far I have invested just over $1,000 and at this rate I am expecting for this project to end up under $1,500 which is a great value when you consider "dumb" LSD are $1,000+ without install and you are still using smaller ring/pinion and half shafts.

$398 E71 Differential with 21,000 miles shipped
$550 F85 Axles and Diff Flanges
$27 ICM Module
$25 QMVH Module
$50 QMVH Wiring Harness
$135 Diff Fluid and Vent Pipe



I for see the wiring being the most challenging. My plan is to use the pigtails to build my own wiring harness for everything. It will be some tedious work to feed wires through a partially disassembled vehicle but it IMO it beats gutting the vehicle to remove/install the main harness. Not to mention there probably isn't a wiring harness which would be applicable for a diesel X5 with an electronic differential since it's never existed. #GuinnaePigLife



I had my X5 up for a slew of suspension upgrades and I took the opportunity to slide the diff under the vehicle and eye it up. X5s and X5Ms essentially have the same underpinnings so I don't see any issue with it bolting up but I will have to rework my axle back exhaust. The diff was only fitted to vehicles with twin pipped exhausts and the X5 has a single 3" system. The electronic diff is very wide with the clutch packs and motors. I foresee contact on the lower passenger side. I could make a hybrid exhaust system and in the midsection mate the single 3" pipe to the dual pipped system from a 50i. Not sure how that would sound and I like the simplicity of a single piped system so I will find a custom solution.


Next Steps
- Swap X6 flanges for F85 flanges
- Find an exhaust solution that will work with the larger diff
- Mount F85 diff and axles to confirm fitment and function. *When the diff motors are unconnected it's essentially a beefy open diff so it should function just like my current unit.
- Get my grubby little hands on the pigtails I can build the harness.


Cheers to cool shit and unique OEM retrofits,
Evan

[RL18]

F#@k yes man. I love it

[ucsbwsr]

Progress Report.

The differential is in and "operational" but not fully functional. Once the output flanges were swapped I could proceed with the diff swap and I am happy to report there were no unpleasant surprises. The flanges swapped, the 35d driveshaft bolts up, diff mounting hardware was the same, etc.

Currently the QMVH harness, diff, and F85 axles are installed so all of the work on the outside of the vehicle is done. Up next will be collecting the necessary pigtails for the interior wiring so I can build a harness which will connect the ICM and QMVH modules with the rest of the vehicle. Sprinkle in some coding and we should be in business. Sounds easy but I am sure the electrical will be more involved than the mechanical work which was just done.

I have a couple test drives under my belt and everything seems "fine" lol. No concerning noises or behavior from the diff which is comforting, it only has 25k on it but you never know with parts from dismantlers. Without chassis integration the diff acts like a normal open diff so dynamics are identical to before.

Here are some pics and info!
Evan

Swapping the output flanges from X6 to F85 was harder than expected. My dual big ass pry bar method wasn't doing the trick so I dropped it off at a local BMW mechanic and they struggled with it for 5 days before returning it, they even had a local foreman stop by to take a look. Once back in my possession I used my new-to-me 5.5lb slide hammer paired with two small metal stakes which preloaded the flanges. The combo go the stubborn flanges to release.




F85 vs X6


Axle comparison




Axles going in


Splines cleaned


Out with the old and in with the new


Wiring harness FINALLY showed up from Latvia 2.5 months later after going MIA with USPS...


QMVH harness routed up and over the subframe from the cargo area.


New vent pipe to replace a broken one


In we go


Fluids that are 1/4 the price of the differential itself, lol, and 6 drain/fill plugs.





Wide Load

[Dawgz]

Wow! Nice work

[aurelmihai]

How far did you get with the project?
Is the front diff the same ratio as the x6 one?

The 3.64 dumb diff here in EU are very expensive because are getting broken after 200k. The used one could go for 1000$ and X6 diff is cheaper.

[ucsbwsr]

Originally Posted by aurelmihai

How far did you get with the project?
Is the front diff the same ratio as the x6 one?

The 3.64 dumb diff here in EU are very expensive because are getting broken after 200k. The used one could go for 1000$ and X6 diff is cheaper.

Project is as far as it's shown in this thread. Mechanically it is installed but electronically it is not complete.

Yes, front diff ratio matches the rear, things would be very bad if they didn't.

[Daytonawim]

Thats a nice pleace of work!!!

[e46IX]

Originally Posted by ucsbwsr

Project is as far as it's shown in this thread. Mechanically it is installed but electronically it is not complete.

Yes, front diff ratio matches the rear, things would be very bad if they didn't.

Any differences in mechanical behavior with the X5M diff in place of the stock one? Even without the wiring/modules/coding.

[ucsbwsr]

Originally Posted by e46IX

Any differences in mechanical behavior with the X5M diff in place of the stock one? Even without the wiring/modules/coding.

No

[addy27]

Awesome project!! Can you check on the ACC parameters in the ICM as cars with ACC come with a separate LDM module vs an ICM. I wonder if this retrofit can be done to cars with ACC.

[gilberjj]

This is amazing! I love the dedication!