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M2 Technical Topics > N55 Engine / Drivetrain / Exhaust / Bolt-ons / Tuning > Active M Differential

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      10-16-2015, 05:18 PM   #1
Spook410
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Active M Differential

Appears the M2 is getting the Active M Differential. While I can't say I like the complexity with sensors and processing (what happens when a sensor breaks?) I do wonder how this will change real world driving. Does this mean we'll get improved traction on snow and ice?
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      10-16-2015, 05:55 PM   #2
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Typically it changes the locking amount of the diff looking at the steering angle and car angle and traction on each tire.

Yes it may help with traction on bad roads.

If you are looking for easy to repair I wouldn't be looking at electronic differentials.

Last edited by HawkZ4M; 10-16-2015 at 06:18 PM..
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      10-16-2015, 06:30 PM   #3
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Given a choice, I would choose something simpler. This also applies to rain sensing wipers and nav systems I don't need. However, I was not consulted on this particular model.

The point is.. this doesn't work like a mechanical differential it may offer some unique benefits across a broader range of circumstances. These are already available in other models. I've read the interviews with designers but haven't seen much real world experience reflected in various forums. Any insights?
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      10-16-2015, 07:04 PM   #4
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The sensors allow it to be pro-active rather than purely reactive like a mechanical diff.
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      10-17-2015, 10:46 PM   #5
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Quote:
Originally Posted by PackPride85 View Post
The sensors allow it to be pro-active rather than purely reactive like a mechanical diff.
I expect that it's still "mechanical", but with the addition of sensors to affect the onset and extent of lock-up.

Anyone have any links to some good tech info on this diff? I'd be interested in learning more about it, and understanding how it's different from standard clutch LSDs that I've come to know and love...
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      10-18-2015, 12:57 AM   #6
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Quote:
Originally Posted by DVC View Post
I expect that it's still "mechanical", but with the addition of sensors to affect the onset and extent of lock-up.

Anyone have any links to some good tech info on this diff? I'd be interested in learning more about it, and understanding how it's different from standard clutch LSDs that I've come to know and love...
http://f80.bimmerpost.com/forums/sho....php?t=1018024
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      10-19-2015, 02:03 PM   #7
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M automobiles have been fitted with locking differentials for several generations but the BMW M3 and BMW M4 are equipped with an Active M differential. What is the 'active' part of the differential?

Active means that a whole range of sensors have been built into the car that are able to identify the road conditions, calculate the optimum locking degree, and activate the lock accordingly by means of an electric motor. The central input variables are the torque, the individual rotational speeds of the wheels, the lateral acceleration and the driving speed. Then there is the steering angle and the yaw rate, plus a few additional factors.
Thanks... Good high-level summary (although more details on lock-up characteristics would be interesting too).
So as suspected, this differential is a fully functional mechanical clutch LSD, but with the addition of sensors and electronic motors to affect how lock-up is applied in reaction to (and proactively, based on) various factors.

In terms of what happens if the sensors/motors fail...my guess would be that it will still function as a standard "passive" LSD without the proactive/enhanced inputs from the M gadgetry.

Last edited by DVC; 10-19-2015 at 02:08 PM..
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      10-20-2015, 03:09 PM   #8
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Quote:
Originally Posted by DVC View Post
Thanks... Good high-level summary (although more details on lock-up characteristics would be interesting too).
So as suspected, this differential is a fully functional mechanical clutch LSD, but with the addition of sensors and electronic motors to affect how lock-up is applied in reaction to (and proactively, based on) various factors.

In terms of what happens if the sensors/motors fail...my guess would be that it will still function as a standard "passive" LSD without the proactive/enhanced inputs from the M gadgetry.
This is a link to the F8X M3/M4 Technical Training docs.

http://f80.bimmerpost.com/forums/sho....php?t=1015603


The differential section starts on page 52. This is shared tech from the current M6/ M5/ M4/ M3.
You will also find details about systems shared on the M2 including DTC, front & rear suspension, servotronic steering, etc.
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