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03-10-2014, 09:04 AM | #1 |
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Euro MDM Coefficient of Friction
Hi all,
So I coded my car to Euro MDM (US_VEHICLE->nicht_aktiv, MDYNAMIC_MODE_USA->nicht_aktiv) recently and noticed that the coefficient of friction values for the oversteering can take multiple values (M3_UEBERSTEUERN_MUE_0 and M3_UEBERSTEUERN_MUE_1_2_M). NCS Dummy has the following Translations for M3_UEBERSTEUERN_MUE_0: wert_00: !(E90+(S65B40+US,S65B44+!US+MAN_UMF_GTS),(E92,E93) +S65B40) wert_01: E90 + S65B40 + US wert_02: E92 + S65B40 + !US + !MAN_UMF_GTS wert_03: E92 + S65B40 + US wert_04: E93 + S65B40 + !US wert_05: E93 + S65B40 + US wert_06: E92 + S65B40 + !US + MAN_UMF_GTS wert_07: E90 + S65B44 + !US + MAN_UMF_GTS And for M3_UEBERSTEUERN_MUE_1_2_M: wert_00: !(E90+(S65B40+US,S65B44+!US+MAN_UMF_GTS),(E92,E93) +S65B40) wert_01: E90 + S65B40 + US wert_02: E92 + S65B40 + !US + !MAN_UMF_GTS wert_03: E92 + S65B40 + US wert_04: E93 + S65B40 + !US wert_05: E93 + S65B40 + US wert_06: E92 + S65B40 + !US + MAN_UMF_GTS wert_07: E90 + S65B44 + !US + MAN_UMF_GTS I left my car to its default value of wert_03 (US ZCP E92) but I'm wondering if to make the real switch to Euro MDM I should not also switch those two parameters to wert_02. I'm also intrigued by that MAN_UMF_GTS and maybe switching to wert_06 to get the GTS friction coefficients? although those might be based on stickier and wider tires (not sure). What might be useful would be for people with different spec'd cars to read their DSC modules (MK60_M3.C08) and post their trace files here so we can compare them. As an idiot I didn't make a copy of the full trace for my own car, but I'll post it later today. Ideally an GTS owner could chime in Disclaimer: Use at your own risk. I'm not responsible for any consequences if you damaged your vehicle as a result of coding. |
03-10-2014, 01:45 PM | #3 |
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wow thanks for the info...sounds like we may be able to fine tune the DSC limits a bit more. Curious to see how the GTS settings would be.
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03-11-2014, 09:36 PM | #4 |
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Here is my trace file from the DSC module, in the state it was before modifying it:
Code:
RPA nicht_aktiv MSA aktiv M3_BAUART wert_08 M3_GETRIEBE wert_00 M3_UEBERSTEUERN_MUE_0 wert_03 M3_UEBERSTEUERN_MUE_1_2 wert_03 MDYNAMIC_MODE_USA aktiv M3_PRE_MSR nicht_aktiv LENKWINKELKENNLINIE wert_02 wert_03 LAT_EBD aktiv US_VEHICLE aktiv POHO nicht_aktiv DDS_PLUS nicht_aktiv ABSCHALTBARKEIT_DSC aktiv DRUCKMODELL_HA wert_00 DRUCKMODELL_VA wert_00 Last edited by d0o0fy; 03-11-2014 at 09:51 PM.. Reason: typo |
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03-11-2014, 10:30 PM | #5 |
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The ! is an operand meaning "not".
02 would likely be the standard setting for euro spec, non GTS vehicles. Selecting 02 will also be like selecting 06 or 07 - the data byte for each one of those is the same in hex, "CD".
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03-12-2014, 09:48 AM | #6 |
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Mike,
Here are the values for the other settings: wert_00: 0x00 (0) wert_01: 0x66 (102) wert_02: 0xE6 (230) wert_03: 0x33 (51) wert_04: 0x26 (38) wert_05: 0x7F (127) wert_06: 0xE6 (230) wert_07: 0xE6 (230) Now the interesting bit, there is an equation that seems to govern the value of coefficient used (in pseudo code): if value < 128 thenHere are the coefficient of friction that are associated with each value:coefficient = 2.5 + (value/64)elsecoefficient = 2.5 + ((value-256)/64) wert_00: 2.5 wert_01: 4.09375 wert_02: 2.09375 wert_03: 3.296875 wert_04: 3.09375 wert_05: 4.484375 wert_06: 2.09375 wert_07: 2.09375 So when you go from wert_03 (51) to wert_02 (230) your coefficient goes from 3.296875 to 2.09375 and therefore decreases. Now it seems that the available values are limited to those 6 here. But I am almost certain that it is possible to fine tune the coefficients by modifying the nettodat directly. Because of the way the equation works, the minimum coefficient possible is not obtained at the maximum value (0xFF) but at 128 (0x80). That would lead to a coefficient of 0.5! After that it's direction the skidpad and see how much of a difference those values make. |
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03-25-2014, 04:41 PM | #7 |
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I set wert_07 and euroMDM and it's pretty cool! I was able to drift out of the car wash with 90 degrees of opposite lock, and it pretty much held the drift for me.
I need to set it back to wert_01 and see what the difference feels like for a direct comparison. |
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03-25-2014, 06:06 PM | #8 |
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Hmm, awesome info thanks for posting. Will try playing around with it.
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03-25-2014, 07:07 PM | #9 |
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I changed mine to:
M3_UEBERSTEUERN_MUE_0 wert_02 M3_UEBERSTEUERN_MUE_1_2 wert_02 After executing then reading it for confirmation, I got this: M3_UEBERSTEUERN_MUE_0 wert_02 wert_06 wert_07 M3_UEBERSTEUERN_MUE_1_2 wert_02 wert_06 wert_07 Did you got that also?
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03-25-2014, 07:22 PM | #10 | |
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Quote:
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03-25-2014, 07:40 PM | #11 |
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ahh okay, sounds good, I suspected something along those lines. Thanks
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06-24-2014, 01:16 PM | #12 | |
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Quote:
Which leads me to my point that I'm not sure it's reasonable to assume that those values are coefficients of friction. First, "mu" in German is still just "mu", not "mue". Second, these values don't make sense as mu values for rubber on pavement, though that could be because the theorized calculation formula is wrong. But third, except for gradual changes due to tire temperature fluctuations, sudden changes from moving from one type of road surface to another, and the difference between static vs kinetic friction, coefficients of friction don't actually change based on driving situation. Your grip to hold your intended line can change, of course, but that's a function of the strength and direction of your momentum compared to where you want to go. And again, what matters when tuning for specific body styles is total friction, not coefficient of friction, the latter of which wouldn't change based on the weight of the car. So that makes me wonder even more what this setting means. I'm also curious what the MUE_0 option changes compared to MUE_1_2_M. Maybe the former is for when DSC is on and the latter is for MDM? I'm just curious why the latter is labeled "1_2_M". Even if you count DSC Off as a mode (which wouldn't make sense here), there are still only 3 modes on the car, not 4 as the 0, 1, 2, and M naming pattern suggests. And lastly, if these settings do in fact control DSC leniency, I wonder what changing only MDYNAMIC_MODE_USA does. Having been to the track several times before and after changing that setting, my car already allows more yaw, but if these other settings do indeed represent hard-coded friction limits, I wouldn't have expected that change without having changed these settings. I know that DSC takes other factors into account to decide when and how to intervene (speed, steering angle, etc), but this still puzzles me. "UEBERSTEUERN" seems to translate to "overdrive", so maybe MDYNAMIC relaxes the threshold for more subtle intervention and the "UEBERSTEUERN" settings determine the threshold for more drastic intervention?
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06-24-2014, 01:28 PM | #13 | |
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I edited the post below to remove the redundant listing of the options for both settings since they translated the same way, and also to replace the operand logic with just the model each setting is meant for:
Quote:
There also don't seem to be any ZCP-specific options anywhere in here either. So where does the reprogrammed DSC that BMW advertised with ZCP come from? I know ZCP has a VO code, but typically the VO is used to determine defaults for settings in these modules, so you'd still expect to see differences in the modules between ZCP and non-ZCP cars.
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06-24-2014, 03:44 PM | #14 | |
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I'm also not sure why there is 2 different values for mu (BTW mu is "my" in German and UEBERSTEUERN means oversteering, not sure about "mue"...), my guess was DSC and MDM. When I first fiddled with the EuroMDM mod, I wanted to make sure that the car was as close as possible to the Euro version as possible and that difference in value picked my interested and I wanted to document it and get the community's feedback. Last edited by d0o0fy; 06-24-2014 at 04:00 PM.. Reason: typo |
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06-25-2014, 02:03 PM | #15 | |
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06-25-2014, 04:14 PM | #16 |
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To update you guys, I also changed two values DRUCKMODELL_HA and DRUCKMODELL_VA to the GTS option in NCSDummy (there are only two, so i'm guessing it was wert_01 since I don't have my laptop with me). NCSDummy describes wert_00 as !MAN_UMF_GTS and wert_01 as MAN_UMF_GTS.
It may just be in my head, but normal acceleration with full DSC on (not MDM) is less intrusive, doesn't cut as much throttle, and keeps you closer to the grip limit. I notice this in 1st and 2nd gear powering out of turns. Can someone else test and verify? Google translate says DRUCKMODELL means Pressure Model. Not really sure what it means still. |
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07-07-2014, 02:36 PM | #19 |
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08-21-2014, 09:47 AM | #20 |
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Z4M E85 Coefficient Values
Hi d0o0fy,
Ultimately I'd like to enable M Track Mode on my Z4M Roadster, but the MK60 module doesn't have the required coding - i.e. TRAKTIONDIFFERENZREGELUNG and DTC_LAMPE. But it does allow the Over/Understeer Frictioin Coefficients and Understeer Threshold to be changed. As for the M3, the coefficients can be set for 0_2 and 1_2. I presume one of these is for DSC on and one for DSC off, but not sure which is which. The reason for the post is I'd like to understand what friction coefficient values the MUE "wert" values relate to. You mentioned you can calculate these from the Pseudo code. Would you mind explaining how you did this so I can calulate the values for the E85. Regards, Meeko. |
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09-09-2014, 08:33 AM | #21 | |
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11-05-2014, 04:23 AM | #22 |
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is it possible to code the Euro MDM to a 335i?
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