Dsc/traction
- Thread starter domsz4
- Start date
While DSC is off, i.e. hold down the button 3 sec., everything is indeed off. In the other 2 modes, nothing is off, only the intervention thresholds change, and their level is speed dependent in either mode. From an old training manual, the 'DTC' mode is explained. It presumes the reader already knows about the default DSC system that was ported directly from the E46.
BMW Training Manual said:
bcworkz said:
+1
Lightning87
Member
about the lsd, as soon as the outside is done, i'm gonna get me 1, yesterday dsc and tsc totaly screwed me up, i didn't have the power to pass a renault laguna, because my tsc cut almost al the power, it was raining and the road was a little slippery, it took until i reached 3rd gear :x
Lightning87 said:
Yup - I have had this problem when launching off from a set of lights ...
* If you are in Normal mode (DSC ON, DTC OFF), the lights change, ... you put your foot down ... and the DSC cuts your power ... and the little fiat whatever next door shoots past.
* For fast launches, I think the SINGLE QUICK PRESS (DSC ON, DTC ON) probably works best together with Sport mode activated ... it doesn't seem to cut the power, the wheels don't seem to spin, and you get lots of traction.
* The LONG 3 SECOND PRESS (DSC OFF, DTC OFF) can also give good results ... BUT it can also give rise to lots of rear wheel spinning and smoke ... which certainly looks impressive, but may not be a fast launch.
Well I guess a bit of intervention is better than the potential embarrassment of flying off the road like a frisbee into a tree. Unless you are certain that you have the skilld of course.
There are 2 good videos of an e92 m3 and a 1M showing why it's not a good idea to switch it all off in the wet even at relatively low speeds.
There are 2 good videos of an e92 m3 and a 1M showing why it's not a good idea to switch it all off in the wet even at relatively low speeds.
It really amuses me to read all the advocates of turning off DSC/DTC on public roads because they say it cuts in too easily when accelerating and then claiming that their skills are superior because they can drive by the seat of their pants.
If these advocates can REALLY drive by the seat of their pants, then surely their driving would be sufficiently refined, so that they would modulate the accelerator pedal to give maximum acceleration with greatest traction without wheel spin, then they would surely discover that they wouldn't initiate the DSC/DTC to intervene? Or am I missing something?
If these advocates can REALLY drive by the seat of their pants, then surely their driving would be sufficiently refined, so that they would modulate the accelerator pedal to give maximum acceleration with greatest traction without wheel spin, then they would surely discover that they wouldn't initiate the DSC/DTC to intervene? Or am I missing something?
I think the general consensus is that DSC is a little over cautious. A bit "nanny state"
Exdos, I agree in principle. However, I find that really fast launches can be tricky with the DSC switched on, especially in slippery conditions. Once the DSC has activated, to stop it cutting engine power it can be necessary to almost completely lift off the throttle before applying the throttle again. With DSC switched off, any slip or spin of the rear wheels can be countered with a subtle modulation of the throttle, balancing available traction with the application of an appropriate amount of power.
Of course, this is more about traction control than stability. On the track, the stability programme panics when shown a whiff of high speed cornering and starts to apply individual brakes unnecessarily. Once familiar with the handling characteristics of the car (and the quality of the tarmac), lap times and cornering speeds are markedly better with DSC off.
Of course, this is more about traction control than stability. On the track, the stability programme panics when shown a whiff of high speed cornering and starts to apply individual brakes unnecessarily. Once familiar with the handling characteristics of the car (and the quality of the tarmac), lap times and cornering speeds are markedly better with DSC off.
The DSC essentially monitors 2 parameters simultaneously: Traction (or loss of) and Yaw angle, and the system allows for an amount of rear wheel slip without intervention by way of the the LSD. If the DSC detects sufficient loss of rear wheel traction then it will cut the drive-by-wire throttle signal until traction has been sufficiently regained. Likewise, if the system detects sufficient yaw angle (i.e . rotation of the car around a central axis as the start of a spin) then it will cut both the throttle signal and apply the brakes to individual wheels (something which no driver can do) simultaneously, until the car regains stability again.
If you refer to my graph (below) of engine RPM versus vehicle speed from datalogging my Z4MC, you can see that in 1st gear the Air:Fuel ratio is leaner than it is in 2nd and 3rd gears, and presumably, this is written into the ECU software to prevent loss of traction when starting in dry conditions. So when it's wet, the driver has to account for the reduced traction available by throttle modulation. Likewise, if you look at a plot of Engine RPM versus speed in any specific gear, you will see that for any given speed there is a matching Engine RPM, therefore there is absolutely no point in flooring the throttle, which might break traction, when instead, you can simply match the throttle position with your right foot to marry the engine revs to the rate of increase of speed by pressing the throttle pedal in a progressive manner through the entire throw until you're at WOT.
Since the DSC is triggered by loss of traction and yaw, in order to drive in a way that allows the DSC to remain on without intervention, you need to refer to the concept of the "Friction Circle" of tyres and avoid breaking traction WHILST YOUR FOOT IS ON THE THROTTLE. However, if you break traction when you're not applying the throttle, the DSC doesn't need to intervene and cut the throttle, except if you increase the yaw too much, when the brakes will be momentarily applied for you, but nothing happens to the throttle. Therefore, if you want to drive fast with the DSC on, but without intervening when cornering, then you exploit the Friction Circle of your tyres, by turning into the corner sharply, slightly earlier than normal, braking first if necessary, with no throttle, so that you get a bit of lift-off oversteer as you enter the corner, which gets the car slightly broadside to the corner. Since you have no throttle input, the DSC can't intervene. In the meantime, because you're not using the rear tyres for accelerating, the tyres devote themselves to giving you more lateral grip and once the car is balanced and cornering (within a fraction of a second) you can then reapply the throttle, matching it to Engine RPM, and if you're going fast enough, you should have all four tyres operating at their optimum slip angle. In this attitude, there is no loss of traction and no yawing, so the DSC has nothing to do. If you then slowly increase throttle, you can explore your lateral grip whilst accelerating through the latter part of the corner to achieve a higher exit speed.
If you refer to my graph (below) of engine RPM versus vehicle speed from datalogging my Z4MC, you can see that in 1st gear the Air:Fuel ratio is leaner than it is in 2nd and 3rd gears, and presumably, this is written into the ECU software to prevent loss of traction when starting in dry conditions. So when it's wet, the driver has to account for the reduced traction available by throttle modulation. Likewise, if you look at a plot of Engine RPM versus speed in any specific gear, you will see that for any given speed there is a matching Engine RPM, therefore there is absolutely no point in flooring the throttle, which might break traction, when instead, you can simply match the throttle position with your right foot to marry the engine revs to the rate of increase of speed by pressing the throttle pedal in a progressive manner through the entire throw until you're at WOT.
Since the DSC is triggered by loss of traction and yaw, in order to drive in a way that allows the DSC to remain on without intervention, you need to refer to the concept of the "Friction Circle" of tyres and avoid breaking traction WHILST YOUR FOOT IS ON THE THROTTLE. However, if you break traction when you're not applying the throttle, the DSC doesn't need to intervene and cut the throttle, except if you increase the yaw too much, when the brakes will be momentarily applied for you, but nothing happens to the throttle. Therefore, if you want to drive fast with the DSC on, but without intervening when cornering, then you exploit the Friction Circle of your tyres, by turning into the corner sharply, slightly earlier than normal, braking first if necessary, with no throttle, so that you get a bit of lift-off oversteer as you enter the corner, which gets the car slightly broadside to the corner. Since you have no throttle input, the DSC can't intervene. In the meantime, because you're not using the rear tyres for accelerating, the tyres devote themselves to giving you more lateral grip and once the car is balanced and cornering (within a fraction of a second) you can then reapply the throttle, matching it to Engine RPM, and if you're going fast enough, you should have all four tyres operating at their optimum slip angle. In this attitude, there is no loss of traction and no yawing, so the DSC has nothing to do. If you then slowly increase throttle, you can explore your lateral grip whilst accelerating through the latter part of the corner to achieve a higher exit speed.
mad4slalom
Senior member
yes definately need to be careful in the m, off is off totally, no two stage button on the m seems some misinformation re traction control :driving:
Or just turn it off and not drive around the DSC? If your capable enough to enter a corner sideways then one would assume your capable of controlling the throttle on the way out :driving:exdos said:The DSC essentially monitors 2 parameters simultaneously: Traction (or loss of) and Yaw angle, and the system allows for an amount of rear wheel slip without intervention by way of the the LSD. If the DSC detects sufficient loss of rear wheel traction then it will cut the drive-by-wire throttle signal until traction has been sufficiently regained. Likewise, if the system detects sufficient yaw angle (i.e . rotation of the car around a central axis as the start of a spin) then it will cut both the throttle signal and apply the brakes to individual wheels (something which no driver can do) simultaneously, until the car regains stability again.
If you refer to my graph (below) of engine RPM versus vehicle speed from datalogging my Z4MC, you can see that in 1st gear the Air:Fuel ratio is leaner than it is in 2nd and 3rd gears, and presumably, this is written into the ECU software to prevent loss of traction when starting in dry conditions. So when it's wet, the driver has to account for the reduced traction available by throttle modulation. Likewise, if you look at a plot of Engine RPM versus speed in any specific gear, you will see that for any given speed there is a matching Engine RPM, therefore there is absolutely no point in flooring the throttle, which might break traction, when instead, you can simply match the throttle position with your right foot to marry the engine revs to the rate of increase of speed by pressing the throttle pedal in a progressive manner through the entire throw until you're at WOT.
Since the DSC is triggered by loss of traction and yaw, in order to drive in a way that allows the DSC to remain on without intervention, you need to refer to the concept of the "Friction Circle" of tyres and avoid breaking traction WHILST YOUR FOOT IS ON THE THROTTLE. However, if you break traction when you're not applying the throttle, the DSC doesn't need to intervene and cut the throttle, except if you increase the yaw too much, when the brakes will be momentarily applied for you, but nothing happens to the throttle. Therefore, if you want to drive fast with the DSC on, but without intervening when cornering, then you exploit the Friction Circle of your tyres, by turning into the corner sharply, slightly earlier than normal, braking first if necessary, with no throttle, so that you get a bit of lift-off oversteer as you enter the corner, which gets the car slightly broadside to the corner. Since you have no throttle input, the DSC can't intervene. In the meantime, because you're not using the rear tyres for accelerating, the tyres devote themselves to giving you more lateral grip and once the car is balanced and cornering (within a fraction of a second) you can then reapply the throttle, matching it to Engine RPM, and if you're going fast enough, you should have all four tyres operating at their optimum slip angle. In this attitude, there is no loss of traction and no yawing, so the DSC has nothing to do. If you then slowly increase throttle, you can explore your lateral grip whilst accelerating through the latter part of the corner to achieve a higher exit speed.
My point on this is that none of us are perfect all of the time and if you do make a mistake when the DSC is off on public roads, you've not got a lot of room (i.e. the width of your own carriageway which is less than the length of your car going sideways) to put things right. Off public roads it's an altogether different matter.RedUn said: