Geeky DSC questions

[pokeybritches]

Let me preface this by saying that I am by no means an avid track day participant. I'd like to be, but my erratic work schedule and my slush fund (or lack thereof) prohibit that right now. I have a few schools in mind to attend later this year because I don't want the added wear and tear on my own car until I know what I'm doing, so my knowledge of racing comes from my father (knows his stuff!) and occasional spirited runs on forgiving rural back roads with good visibility. Basically, I can push the car to 80-90% pretty well (and recover it if things get out of hand), but I am not good enough to wring this thing out to its full potential like many of the regulars on here. I've been taught how to get myself out of trouble, but not how to put down the best lap times. Some of what I'm going to suggest may not be practical, and I'd like to be corrected and learn. I posted in this section because I figured its where the most driving talent lies.

I was wondering if anyone knew where I could find some of the nitty-gritty details about the DSC's thresholds. I have an engineering background and a basic understanding of how the system works, so I'm looking specifically at the software and formula they use for intervention (and maybe even the level of intervention). For example, maximum angle, rate, rate acceleration, etc.

The reason I ask is (in my limited experience) I think the DSC could be significantly improved if a greater emphasis is placed on yaw acceleration, and less on the angle itself. In other words, weigh acceleration more than position. A rapid increase in yaw rate is one early sign that a car will quickly be unrecoverable, such as the rear end snapping out. As my dad always said, "Smooth drivers win races." Are there times when an enormous acceleration in the yaw axis is beneficial, such as snapping it out quickly and not-so-smoothly? Increasing the threshold for slip angle (correct term?) would allow small controlled slides. What I'm assuming is: car rapidly starts to rotate = unintended effect... car slides smoothly within certain limits = car is still under control, don't do anything.

The following prompted this post:

The only time I've ever had this car scare me was when I hit a wet spot (from a broken sprinkler) on a 270 degree onramp. I wasn't going too fast and I wasn't riding the limit by any means, but I did underestimate the loss of traction that would result from that one small puddle and kept in partial throttle. The back end snapped sideways, and the only thing that saved me was a quick over-correction and subsequent recorrection. I never felt any intervention from DSC, and I feel like the car would've been perfectly content discovering its 4-wheeling abilities. I'm not one to test the DSC's safety net and expect its holy hand to gently pluck me out of my troubled spot. I was very disappointed, though, because the only thing that saved me was all that illegal hot-rodding I did as a teenager in a 1987 Nissan Maxima around uninhabited, preplanned neighborhoods still under construction. Had I not had a basic understanding of car control and a quick reaction, my M would've gone for a little trip (with me in it!).

I'd like to learn how BMW weighs DSC's inputs for my own dorky curiosity. It should be entirely possible to have a DSC setting that's actually useful on the track, and another one that is more beneficial on the street. It seems to me it's all programming because the hardware is already in place... which is kind of frustrating but an opportunity at the same time. Don't get me wrong, I'm not planning on "cracking BMW's code" and reprogramming my DSC. I would like to get to the point where I can send an intelligent suggestion to BMW, heard or not, for my own interest and satisfaction. Who knows, maybe a reflash will be available one day that allows cycling of different DSC settings via the button. Haha, wishful thinking, but can anyone shed some light on this or send me in a helpful direction? Maybe useful DSC will save an M or two:

http://www.youtube.com/watch?v=vPEOXG-5w0g

[Tonybest]

Wow. Very interesting topic and I will only post this in order to give a free bump to your topic.

All I know, BMW would never want you to be able to alter the DSC settings of your car. I know you did mention that you weren't planning on doing so.

In the M (coupe or roadster) the DSC is either on or all-off, as opposed to the e90s DTC-DSC that have 3 settings but no "all off" setting.

I'm now on my third year tracking cars and the only way I do it is "all-off" except when there is rain, or its my first session on a new track. Our cars are built and equipped for very spirited driving. So when you start in this sport, do so in a gradual and a controlled manner. You will enjoy it tremendously.

[psygnosis]

Is the DSC on the M (and all 2006+?) different from my 04 sport? I have 3 settings, normal haven't touched anything full on, press it once for the dsc light to turn on, press and hold to get the orange ! triangle and turn it off completely (and unleash the full fury of my one tire fire)

[Tonybest]

Originally Posted by psygnosis

Is the DSC on the M (and all 2006+?) different from my 04 sport? I have 3 settings, normal haven't touched anything full on, press it once for the dsc light to turn on, press and hold to get the orange ! triangle and turn it off completely (and unleash the full fury of my one tire fire)

Yes different . In my case, it's all-on if I don't touch it, and then I press it for 1 sec (to make sure I guess) and the DSC logo comes on and it's all-off.