[padders]

Not sure that is true. I believe the e-diff, which in essence is just single rear brake intervention is only operative when both DSC or DTC are off ie when there is no other traction control and therefore isn't active very much at all in fact. It is a very pale imitation of a real slippy diff.

It's surprisingly active in the background though, without any warning lights showing on the dash, especially in the wet. After a few hundred miles of spirited driving in the winter there is often far more brake dust on the rear wheels than the front, if that's anything to go by.

E-diff is the base layer and is active in every mode, including DTC and DSC OFF. It is always on, can only be coded out, as already mentioned.

Also as mentioned, the evidence is by the excessive brake dust from the rear brakes, or the mileage in iDrive showing that the rear brakes required replacing sooner and sooner.

That's not what the m-lite FAQ sticker here says. It says EBD is only active for DSC totally off. I can't say I've ever noticed any EBD intervention with TC on when driving my 125d which had no LSD. All the TC modes inc EBD use the rear brakes so I don't think dusty wheels is all that indicative of the activity of one over another.

 

[Jahjaman]

I thought that engaging TRACTION* was just for snow, snow chains, gravel and sand? In my Owner's Manual it says that you should disengage TRACTION once you're back on tarmac. It's the process of disengaging DSC by activating DTC isn't it? This maximises eDiff intervention - so as to minimise wheelspin in snow etc.

Whereas minimising the eDiff intervention as much as possible when on tarmac is achieved by pressing the SPORT button repeatedly until SPORT+ appears on the display. And while this also engages DTC it's operating the eDiff in the opposite way: it will intervene to a minimum.

I'm not saying I have any of this right: just interested in the clarification.

[*By pressing the car-with-wriggly-lines-OFF button for a couple of seconds, in Comfort mode].

Conceptually, none of what you said is accurate.

Think of it this way:

Layer 1 (top layer) - traction control and stability control, which works by LIMITING ENGINE POWER.

Layer 2 (middle layer) - limited traction and stability control, which works by only APPLYING BRAKES to limit excessive wheelspin.

Layer 3 (base layer) - e-diff, which works by APPLYING BRAKES TO REAR WHEEL when there is a difference in rotational speed between left and right. It does NOT limit excessive wheelspin. It only seems to equalise rotational speed so that only the free spinning wheel is slowed down.

DSC OFF - only uses Layer 3
DTC mode - uses Layer 3 and Layer 2
Sport+ mode - uses Layer 3 and Layer 2
Comfort/Sport mode - uses Layer 3, Layer 2 and Layer 1.

As you can see, the e-diff is always present in every drive mode. It's just that you can't feel the e-diff in Comfort because the other Layers intervene well before the e-diff becomes apparent.

 

[Jahjaman]

That's not what the m-lite FAQ sticker here says. It says EBD is only active for DSC totally off. I can't say I've ever noticed any EBD intervention with TC on when driving my 125d which had no LSD. All the TC modes inc EBD use the rear brakes so I don't think dusty wheels is all that indicative of the activity of one over another.

M Lite table is mostly correct, but not 100% correct.

There are other anomalies in the table that are not accurate.

It was created a long time ago.

 

[padders]

That's not what the m-lite FAQ sticker here says. It says EBD is only active for DSC totally off. I can't say I've ever noticed any EBD intervention with TC on when driving my 125d which had no LSD. All the TC modes inc EBD use the rear brakes so I don't think dusty wheels is all that indicative of the activity of one over another.

M Lite table is mostly correct, but not 100% correct.

There are other anomalies in the table that are not accurate.

It was created a long time ago.

Agreed but I am not as yet convinced that it is wrong in this case. I think if DSC were active, it's function and purpose to quell wheel spin and pull the car straight would overrule any diff function which might act to destabilise the car. There may be an incidental diff effect of course. I can see sense in having it only act as purely as a lsd when Tc and stability functions were disabled. After all, all the systems do is snatch a rear brake*, it's the timing and cause that differ.

* and cut power maybe in the case of DSC/DTC

 

[Chapscrap]

Jahjaman, your layers explanation is one that even I, a bit of a Luddite, can understand. It makes absolute sense, and is borne out by my own experiences with the car over the last 15 months or so.
Cheers.

 

[Ja50nK]

Interesting. So whilst not required, is there benefit to coding off the e-lsd if you have a mechanical LSD fitted? If so, how would you do it?

Still interested in others opinions, but I reckon the mechanical LSD will mean it is very unlikely the circumstances where the e-lsd will intervene will occur?

Sent from my SM-N986B using Tapatalk

 

[nastypoker]

Interesting. So whilst not required, is there benefit to coding off the e-lsd if you have a mechanical LSD fitted? If so, how would you do it?

Still interested in others opinions, but I reckon the mechanical LSD will mean it is very unlikely the circumstances where the e-lsd will intervene will occur?

I haven't noticed the E-diff biting at the brakes since I had my LSD installed but I am no pro driver. I think your logic is correct that the mecanical diff will intervene before one wheel slips therefore the e-diff shouldn't ever activate.

 

[Trojantrow]

E dif is reactive , LSD is proactive.

e diff can't engage as it doesn't get to a point that it sees anything wrong

Sent from my iPhone using Tapatalk

 

[msej449]

@Jahjaman Thanks, that's really what I was after. Much better than the narrative in the Owners Manual. And I suppose you can view the LSD as a Layer 0 - A proactive, physical device that intervenes well before the electronics do. If the LSD can't compensate for an issue, then in effect, the electronic Layers 1 to 3 take over.

And mentioned by others, since I had the LSD installed I have almost never seen/felt any of the electronics intervene.

 

[Dizeee]

I hate to say this but there is a different explanation to why the rear wheels get dirtier in wintery weather compared to the fronts, and that is due to the fact that road debris and residue is vortexed to them by the front wheels and spray.

I am not saying anything above is inaccurate ( to be fair I actually am a little lost with some of it as I thought DTC off / DSC off were the same thing ) but you will generally find the rear wheels to be filthier after a winters drive owing to the continual stream of rubbish that envelops them.

Maybe jahjaman can explain the DTC / DSC options, isn't one where you hold it down for a few seconds? Its quite poor that I am having to ask this as I could have just read the manual, but this forum is better than a manual!

 

[Neil-D]

This is getting very complicated 😂
As I understand it and have experienced, a single press on the DTC button disables traction control, therefore you could put a pair of 11's down in rubber provided you're generally in a straight line.
Sideways movement determine on wheel speed, throttle and steering angle will start to pull you straight provided momentum hasn't taken over.

A long hold of the DTC button kills both that traction control as well as the stability control(DSC off), therefore you're on your own.
I've never felt any Ediff of whatever it is take over in this mode, just the inside wheel losing traction. Perhaps it's very subtle.

With the LSD and DSC off the back end of the car feels just like that it my previous M cars, just with less finesse.

 

[Aadil717]

I hate to say this but there is a different explanation to why the rear wheels get dirtier in wintery weather compared to the fronts, and that is due to the fact that road debris and residue is vortexed to them by the front wheels and spray.

I am not saying anything above is inaccurate ( to be fair I actually am a little lost with some of it as I thought DTC off / DSC off were the same thing ) but you will generally find the rear wheels to be filthier after a winters drive owing to the continual stream of rubbish that envelops them.

Road grime is of course a cause of dirty wheels, but it's actual brake dust you can see on both axles, more obvious on a clean car after a spirited drive in summer I guess.
Plus the fact that the rear disc brakes are larger than the fronts, I do think that they are always working and the dust is a clear indication of this.

 

[Chapscrap]

Re: Dirty back wheels.
I quite accept that some of the dirt on the rear wheels is aerodynamics at work, however on every other car I've owned (including BMW's and Mini's) the front wheels are black with brake dust and the rears are reasonably clean after a couple of hundred miles of being cleaned. The 140 is the exact reverse of this, leading me to think the rear brakes are being worked hard. It's not scientific, just an observation, and does fit with the ediff theory.

 

[Dizeee]

I have never really consciously looked but will now do so. FWIW, as a cleaning obsessive, I am doing my wheels around twice a week and have done since April. Its my fronts that are dirtier than the rears as far as I can tell - however, I should also add that my front pads are almost non existent so that be contributing. But there is brake dust that appears on both.

 

[padders]

Re: Dirty back wheels.
I quite accept that some of the dirt on the rear wheels is aerodynamics at work, however on every other car I've owned (including BMW's and Mini's) the front wheels are black with brake dust and the rears are reasonably clean after a couple of hundred miles of being cleaned. The 140 is the exact reverse of this, leading me to think the rear brakes are being worked hard. It's not scientific, just an observation, and does fit with the ediff theory.

And also the fact that all the TC/stability suite, ie Bosch ESP works off the back brakes. I still don't agree it is down to the supposed constant EBD or e-diff if you will. The more powerful the car, the more often ESP (DSC) has to intervene. On an M-lite without LSD on MPSS, it is very often indeed.

 

[Nik Gnashers]

I get more brake dust on my fronts than my rears.

I'd just like to say also, I wouldn't drive in sport+ in the wet either. I still have the open diff, and with a 411bhp/576nm remap, the rear wiggles around a fair bit in the bone dry, so not a chance would I sport+ it in the wet !

 

[Jahjaman]

I suppose you can view the LSD as a Layer 0 - A proactive, physical device that intervenes well before the electronics do. If the LSD can't compensate for an issue, then in effect, the electronic Layers 1 to 3 take over.

Layer 0 is a good descriptor

Cheers.

Awesome

E dif is reactive , LSD is proactive.

e diff can't engage as it doesn't get to a point that it sees anything wrong

Not from historical analysis, no.

E-diff is algorithm based and is also proactive. It works before slip is detected. It does so by predicting when slip will occur and tries to prevent it from happening.

https://www.1addicts.com/forums/showthread.php?s=2a421bad513a01238b83f65d7ac1eda1&t=719012

This car was equipped with a mechanical LSD as well - so even with a mechanical LSD, the system still provides additional inputs.