First of all, great work! I read the whole thread but I got to be honest, there is a lot of information and I want to be sure to understand everything right...
In M1, DTC button is wired directly to DSC, so there is no rewiring required? But DTC button is not enabling MDM, as there is a second button on steering wheel?
I just want the DSC MDM, everything else like steering EDC, ... is not important for me. Also I own a 330, not a 335, so there is no MHD available. I'm wondering whats the easiest way to get the DSC in MDM.
As far as I understand, I need additional hardware like superwoofys project to send 0x399 message, right? M1 and M3 DSC software wohld work both, the only difference is that I need to rewire the DSC Button with M3 software? Is there any difference in drivability?
Thanks in advance and again, great work!!
Yes, in the 1m MDM is only activated by the a short pres of the DSC button on the dash, not the M button on the steering wheel unlike the M3
If you are only interested in having mdm instead of dtc in a non-M e8/9x 6cylinder (mk60e5) the easiest true way is as is being discussed by using 1M/M3 dsc flash.
However because of the physical differences between a e8/9x ///M & non-m cars that the DSC system has values that quantify these specifics that are crucial in its operation which are programed to it and they heavily effect the what/when/how/why/where of it's interventions, like the values that it uses to obtain the fundamental steering (steered) angle from the drivers steering wheel angle, mean that this method is not without potential issue/s of its own.
Although for some, like those who don't want or use DSC-on and simply want to have the availability of a less intrusive DTC this is not so much of an issue, although it would likely not be completely issue free.
For a single example from the vast potentials: the difference in the actual steering angle and that calculated would mean as soon as there is steering wheel angle it will think the car is understeering, which could lead to false interventions for it, that although may not be directly felt by the driver may lead to other issues for example increased brake temps and/or wear or even just dirtier wheels more often...
For those with the retrofitted 1M/M3 steering rack and/or associated components of the steering system that effect the relationship between the steering wheel and the steered angle. The remaining physical differences that are cared for in the DSC would have a negligible effect that is outweighed by the minor advantages of having actual MDM.
It is possible for these physical differences to be coded (beyond the scope of this intial post).
However the simplest way to achieve something similar to MDM without effecting the models inside the DSC is to adjust the coding in the DSC so that DTC operates the same as MDM...
(you can also make MDM more like DTC the same way lol).
But first it is best to understand some very basics about DSC, DTC and MDM.
DSC quite simply is BMWs electronic stability control system (ESP/ESC). ESC incorporates the many subsytems like ABS and TC etc, etc, etc, but it is important to understand there difference in operation when as subsytem of ESC which is fundamentally different to there original operation.
ESC is a safety system that very basically, is designed to help the vehicle follow/align to the drivers desired path and trajectory and prevent/correct instability while doing so.
To put into context, originally ABS in a max braking scenario, was designed to prevent/correct a wheel/s from lockup under braking. But as a subsytem of ESC it is designed to here maxmise the overall deceleration by controlling the individual braking while also maintaining/correcting instability and while following/aligning to the drivers desired path. Which subsequently it would obviously prevent lockup in doing so (except for the very specific conditions where lockup would be within these bounds, like snow/ice).
As I'm sure you can now imagine it would be a bit much to try and explain the logic behind all of the subsytems and ESC here...
But very basically ESC compares:
The vehicles actual state and trajectory.
The drivers desired state and trajectory.
A modeled state and trajectory of the vehicle.
DTC is dynamic traction control.
And...
MDM is dynamic traction control.
The main difference between DTC and MDM is actually due to a slight difference in the operation of DSC but it's effect is amplified when in DTC/MDM mode.
In a non-m e8/9x 6cylinder, in normal DSC mode, acceleration wheel slip would be prevented/corrected to prevent/correct instability while still following/aligning to the drivers desired path/trajectory.
Where as:
In a 1M/M3, in normal DSC mode, acceleration wheel slip would be prevented/corrected to maintain/regain stability while still following/aligning to the drivers desired path/trajectory.
Spot the difference?
Comparing DTC to MDM with the small difference in DSC operation:
In DTC mode, accel wheel slip is intially not prevented/corrected but the rest of the non-m DSC sequence remains. As the vehicle speed increases from the lower threshold* the amount of wheel slip prevented/corrected increases up to a point where it is the same as normal non-m DSC
*10-120kph roughly from my testing.
In MDM mode, accel wheel slip is intially not prevented/corrected but the rest of the 1M/M3 DSC sequence remains. As the vehicle speed increases from the lower threshold* the amount accel wheel slip prevented/corrected is increased up to a point where it is the same as normal 1M/M3 DSC.
*25-200kph roughly from testing/documentation.
So DTC and MDM are basically the same thing, albeit with different thresholds
And although (non-m) DTC doesn't intially prevent/correct accel wheel slip, because it will still prevent instability from this means (unless your not going very fast and are going basically dead straight and have lightning fast, precise steering reactions) the difference between 1M/M3 & non-m DSC in reality make a very noticeable difference between DTC and MDM making the later a rather desirable function while the prior is rather useless.
It should also be noted there are a lot of other differences between the calibrations of 1M/M3 and e8/9x 6cylinder that have an effect on the what/when/how/why/where of normal DSC intervention which also will subsequently then effect DTC/MDM..
From simple things like that the parameters of the einspurmodel for 1M/M3 will obviously be higher performance, meaning the thresholds for intervention based on the modelled path/tracjectory will be reached at higher points. To things like the gradient for intervention gain vs speed. And the higher base thresholds for under/oversteer, that the well known of coefficients labeled in the coding relate to and the way in which interventions control engine and brake torque and the use of them for intervention etc, etc, etc...
The coding parameter that effects DSC as detailed above is "PRE_USC", on is 0x00 (non-m), off is 0x01 (1M/M3), address: 0x300003 mask 0x80
I have thought long and hard about sharing proper info on DSC... as Im sure most can imagine the combination of openly available info and this aspect of a vehicle has an amount of risk. Hence there is a lot of basic info and not a lot given away here. But I am happy to help further so if you have any specifics id be happy to help here. If someone has 1M/M3 rack retrofit with non-m DSC and wants to correct it I have a way but need info.
Or for anyone compotent behind the wheel that will use the system off road with more accurate measurements for analysis than the seat of ones pants it might be more efficient to message direct.
Obviously there is risk in doing anything, but the above is just info.
