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  • Dynamic Stability Control

    Originally posted by Chris View Post
    I'm not sure I agree with this. Sure when you are driving on the roads you shouldn't ever be driving right up to the limits of what the car is capable of, so your driving style could probably be adapted to work with the DSC and never see it is a problem.

    However when you are on a track and want to push to 100% of what the car is capable of performance-wise, there is no way that the DSC wouldn't intervene and thus dampening the experience for drivers who don't want any mechanical interference. If you take your car on the track and don't want to drive completely on the limit, im sure it can be ok.
    I may be wrong on this but it seems to me that many people are of the impression that a car is not performing at 100% unless it is powersliding or drifting around every corner and you are steering by looking out of the side window. If that's what they want, then TC / DSC is not for them. Personally, I don't think that that style of driving is the optimum way of getting 100% performance, for me, maintaining the balance and traction of the car is the best technique.

    Take a look at the graph below; it's taken from data from my MC's ECU during acceleration in 3rd gear under WOT as recorded by my datalogger.



    In this graph, I floored the accelerator at around 1900rpm with the DSC on, and as you can see the engine response is immediate and that the rate of engine acceleration is almost perfectly linear throughout the rev range, showing that I was getting the same level of traction of the rear tyres on the tarmac throughout the rev range with no/minimal slipping, even when the full power was first applied.

    So, if traction can be maintained, the DSC doesn't intervene, and that means around corners as well as in straight lines. Since the S54 MC also has a 25% limited slip differential some difference in traction on the two rear wheels is also permitted by the DSC, as it is in the S50. Therefore, if you can drive in a style which maintains both balance and traction then the DSC has no reason to intervene. This happens both on track and on public roads, because the physics is the same in both environments.

    The DSC acts by temporarily cutting the power and/or applying the brakes to individual and/or all the wheels to prevent an impending serious instability/loss of traction/grip. It's my experience of the DSC on the S54 that the factor which initiates the DSC the most is excessive yaw. From my participation on this forum for the past 5 years I notice that a number of S50 owners have found themselves pirouetting in their S50 MCs through 360 degrees when the yaw rate has become excessive, and this happens so quickly that it catches the driver out. From what has been posted on this forum, this has occurred on both public roads and on track, therefore some MC owners have unwittingly driven their MCs at above "100% of what the car is capable of performance-wise", otherwise they wouldn't have lost control. So why has this happened?

    In the wet, it is obviously easier to lose traction than on dry tarmac, therefore to maintain traction in the wet, it is more imperative to maintain the balance of the car and to make weightshifting as smooth as possible under acceleration, braking and cornering, because once traction is lost in the wet it is harder to regain than in dry conditions. If you do this right then again, the DSC on a S54 MC has no need to intervene so you're in the same situation as the driver of a S50 MC under control.

    For me, the greatest weakness in the OEM MC is the excessive bodyroll because the suspension set up is inadequate for the engine power. The excessive bodyroll can cause the car to become suddenly unbalanced and thus permit the MC to suddenly exceed "100% of what the car is capable of performance-wise" and the DSC can prevent some of the spins and pirouettes that would otherwise occur. However, if you considerably reduce bodyroll by suspension modification, then you prevent the bodyroll that causes the sudden weightshifts that can cause many of the losses of balance that would otherwise cause loss of control.

    Over the past 3.5 years I have systematically and progressively modified the suspension on my MC so that it is now fully adjustable front and rear for height, camber, toe, caster, bump and rebound, and with bracing and stiffer bushing all round so that the car's dynamic geometry remains as close as possible to the static geometry to which it is set. Consequently, it is now easier for me to preserve the dynamic balance of the car because the weightshifting is much reduced, which in turn prevents loss of traction under power to the rear wheels and increases lateral grip during cornering, and as such, the DSC has even less reason to intervene than it would without these changes. Therefore my MC can go around a track with tyres screeching away without the DSC ever needing to intervene, partly due to the improved handling characteristics from my suspension/aerodynamic modifications and partly from my own driving style, which is probably somewhat different from yours because I've now driven some 300,000 or so miles on the twisties in all conditions over the past umpteen years.

    For interest, I've produced the graph below which shows the lateral G-force at speed versus corner radius.



    If you look at the green line, which is a plot for 1G, you will see that your car will be pulling 1G at 30mph around a corner with a radius of 18metres, 50mph around a corner with a radius of 50metres, 70mph around a corner with a radius of 100metres and 100mph around a corner with a radius of 200metres, and so on. Therefore, if you measure the radius of an arc of a corner that you measure in Google Earth and know the speed that you travel around that corner, you can fairly accurately estimate the lateral G-force that your car can achieve. It is therefore quite a simple task to look at the graph and see how, say, driving at 30mph around a rounadbout (in a private car park denoted by cones, of course) will translate to the speeds you can achieve around all other corners of known radius for (private) roads and on track. As you can see, there's about a 20% difference in speed around a corner between 0.9G and 1.1G, therefore if you can increase traction and grip in anyway (driving style and/or car mods) you'll increase your cornering speed significantly, which in turn will increase your (car's) performance.

    Hope this helps.
    /// Exdos ///
    "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

  • #2
    Just to throw another thing in, the amount of friction is greater static than moving for the same object. This means that the force needed to make something move is greater than to keep it moving. Therefore the amount of grip you have with the tyres sliding is less than if they are not !

    On balance the DSC is a good thing to have, the only thing I wish is that it was more discreet when you have turned it off. I know its supposed to let you know its off but if you are driving at night its really annoying. I expect the designers only expected it to be turned off on the track and therefore you wouldn't usually be driving at night.

    The system does appear to be a little crude but I think this is an illusion to some extent as the transition between grip and slide is quite sudden in the MC compared to say an M3 with the same system. It therefore intervenes more than in an M3 or newer BM due to this. Once you are sliding though it does seem to work well in terms of not letting the car spin.
    Ex 2001 S54
    New cars:
    Lotus Carlton
    350Z

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    • #3
      Originally posted by MGR View Post
      Therefore the amount of grip you have with the tyres sliding is less than if they are not !
      Therefore if your tyres are screeching (i.e. moving laterally with some loss of grip) the DSC on the MC isn't spoiling your fun at that stage. Instead, it's discretely waiting until there's some rapid change in yaw.

      Originally posted by MGR View Post
      The system does appear to be a little crude but I think this is an illusion to some extent as the transition between grip and slide is quite sudden in the MC compared to say an M3 with the same system.
      I would suggest that this is due to the trailing arms on the MC being distorted slightly in their rubber bushings during lateral loading, whereas the E46 rear suspension is more complex and better suited to resist lateral loading. If you see what I mean.
      Last edited by exdos; 05-12-2008, 05:19 PM.
      /// Exdos ///
      "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

      Comment


      • #4
        where did that come from?

        It's very obvious that and powersliding will scrub speed.

        Thanks for enlightening us.
        Ex 'V3RY M - MCoupe track monster'
        New toys

        Porsche widebody project

        Cayenne Diesel

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        • #5
          Originally posted by Lee View Post
          where did that come from?

          It's very obvious that and powersliding will scrub speed.

          Thanks for enlightening us.
          No problem
          Ex 2001 S54
          New cars:
          Lotus Carlton
          350Z

          Comment


          • #6
            Originally posted by Lee View Post

            Thanks for enlightening us.
            My pleasure
            /// Exdos ///
            "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

            Comment


            • #7
              I've never driven a Z3M with DSC but most factory traction control systems don't allow any slip at all and you DO need some slip (which is usually undetectable by the driver) for best performance on track.

              With the Racelogic system if I put it on "Wet" this is supposed to be no slippage and be like a factory system (although it uses progressive fuel cut rather than brakes/throttle cut) and on a dry track you can feel it "tugging" coming out of tight corners as it's preventing wheelspin and feels slightly held back (although it is no foolproof and the tail would still slide out at Oulton Park on wet setting but I think I had the wrong tyre sizes set). If I put it on "Dry" which is the next setting down it allows 5% slip and you just CANNOT feel any movement of the back end or wheelspin and neither feels held back. Whether the DSC isn't quite strict as Racelogic on "wet" as does allow for slight slip I don't know.

              Comment


              • #8
                Originally posted by c_w View Post
                I've never driven a Z3M with DSC but most factory traction control systems don't allow any slip at all and you DO need some slip (which is usually undetectable by the driver) for best performance on track.

                With the Racelogic system if I put it on "Wet" this is supposed to be no slippage and be like a factory system (although it uses progressive fuel cut rather than brakes/throttle cut) and on a dry track you can feel it "tugging" coming out of tight corners as it's preventing wheelspin and feels slightly held back (although it is no foolproof and the tail would still slide out at Oulton Park on wet setting but I think I had the wrong tyre sizes set). If I put it on "Dry" which is the next setting down it allows 5% slip and you just CANNOT feel any movement of the back end or wheelspin and neither feels held back. Whether the DSC isn't quite strict as Racelogic on "wet" as does allow for slight slip I don't know.

                Don't know to be honest. I would turn it off in the dry on a track unless its the ring where there is no run off and changing conditions on track.

                It does seem to allow some slip as the back end can come out before it comes on. Maybe it allows the 25% at the back ? I've been in jasons MR with the racelogic and it does work in a different way. I've not driven mine on track in the dry with the DSC on apart from the ring. I think the racelogic sems to be more suited to the track as it doesn't seem to hold the engine back for a long as the DSC when it does detect a slip.
                Ex 2001 S54
                New cars:
                Lotus Carlton
                350Z

                Comment


                • #9
                  c_w,

                  What sensors are used with the Racelogic TC system? Do these come with the Racelogic kit?
                  /// Exdos ///
                  "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

                  Comment


                  • #10
                    Previous thread

                    http://www.z3mcoupe.com/forum/showthread.php?t=5880
                    Strongstrut CL front brace-Yellowstuff pads/Castrol SRF race brake fluid-Rogue top mounts/Rear support bushes-H&R ARBs-Whiteline droplinks-Bilstein Sport shockers-H&R Springs-Black Halo Angel Eye headlight units-Sachs lightweight flywheel/matching clutch-Supersprint exhaust/race catalysers-BBS RSGTs with Falkens-K&N High Flow Air Filter-Recaro Pole Position seats - Exdos mod - ACS flippers

                    Comment


                    • #11
                      Originally posted by exdos View Post
                      c_w,

                      What sensors are used with the Racelogic TC system? Do these come with the Racelogic kit?
                      It's all based on wheelspeeds (it taps in to the ABS sensors), you set what the driven wheels are and it knows when you turn a corner as the outer wheels more slower etc. Using these it can also be used as a datalogger at a circuit for example (but I've not used this) or for real time mapping (as in graphs) for rpm and speed. When the driven wheels start to turn faster than the fronts it starts to use fuel cuts. It can be set up differently with a laptop but I've left it all as default after setting the wheel/tyre sizes.

                      Comment


                      • #12
                        Originally posted by c_w View Post
                        It's all based on wheelspeeds (it taps in to the ABS sensors), you set what the driven wheels are and it knows when you turn a corner as the outer wheels more slower etc. Using these it can also be used as a datalogger at a circuit for example (but I've not used this) or for real time mapping (as in graphs) for rpm and speed. When the driven wheels start to turn faster than the fronts it starts to use fuel cuts. It can be set up differently with a laptop but I've left it all as default after setting the wheel/tyre sizes.
                        Seems like the DSC has the potential to be better due to having yaw sensors etc. The racelogic seems to be just a traction control device. I suppose the intended use is different for the set up. It would be interesting if you could re calibrate the DSC maybe like the M mode on the CSL.
                        Ex 2001 S54
                        New cars:
                        Lotus Carlton
                        350Z

                        Comment


                        • #13
                          The data logging aspect is an interesting secondary feature.

                          What level of slip setting do you normally use for everyday use of your MC?
                          What level of slip setting do you use for trackday use, or do you turn it off altogether in the dry?

                          Have you done back-to back comparisons of your lap times at the different settings available on the RLTC on the same trackday when you're "in the groove" to see if, or by how much the TC can help or hinder your track times?

                          Why did you decide to fit a TC system at all?
                          /// Exdos ///
                          "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

                          Comment


                          • #14
                            Personally I don't use any traction controls when I'm truly driving any car. My MC obviously doesn't even have. Anyway, I think DSC's problem is that when you reach the limit and it kicks in it just keep slowing you after the moment is over.

                            But who want to drive MC without watching out from a side window? ;)
                            S50 - '99 Imola Red/Red-Black
                            Mods - KW V3, Powerflex Bushes, Wiechers Strut Brace, H&R ARBs, FOX exhaust, KT4 New Racer 18" wheels, Pagid racing brake pads (yellow), Motul rfb600 racing fuids, untill now ;)

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                            • #15
                              Originally posted by Speedou View Post
                              Anyway, I think DSC's problem is that when you reach the limit and it kicks in it just keep slowing you after the moment is over.
                              Beautifully summed up. If you are on track with the DSC on and you have gone into a corner quick, then nothing happens (so long as you don't get your braking wrong). However, when you are coming out of that corner still on the limit, and put your foot down, the TC stops you dead. It's like standing still for 2 seconds. You have to straighten up before it allows you to apply acceleration again. It is incredibly intrusive/nanny state. Yes, your lap will be significantly slower than without DSC.

                              Which is why 1-5 variable Racelogic has to be correct (or no traction control atall if you feel no need for it, even in the snow in which case you are stupid).
                              Strongstrut CL front brace-Yellowstuff pads/Castrol SRF race brake fluid-Rogue top mounts/Rear support bushes-H&R ARBs-Whiteline droplinks-Bilstein Sport shockers-H&R Springs-Black Halo Angel Eye headlight units-Sachs lightweight flywheel/matching clutch-Supersprint exhaust/race catalysers-BBS RSGTs with Falkens-K&N High Flow Air Filter-Recaro Pole Position seats - Exdos mod - ACS flippers

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