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Learning About A DCT

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  • #31
    So a DCT acts like an electronically controlled manual trans correct? So for launching purposes or launch control it can be programmed to hold higher rpms than your standard tc auto and it can slip the clutch (like a manual) to manage the traction on launch? We know it’s faster shifting in a straight line but is it also programmable to launch much more affectively then a standard auto? This could make a lot of sense why Ford went DCT.

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    • #32
      Originally posted by TtiME View Post
      So a DCT acts like an electronically controlled manual trans correct? So for launching purposes or launch control it can be programmed to hold higher rpms than your standard tc auto and it can slip the clutch (like a manual) to manage the traction on launch? We know it’s faster shifting in a straight line but is it also programmable to launch much more affectively then a standard auto? This could make a lot of sense why Ford went DCT.
      My post #14 talked about this a bit. The programming is built into the ECU's by the engineers and they'll provide the best they can within the limits of the drivetrain.

      The current Golf R is a great example because the identical car is available with either a manual or DCT trans. Two things to note:

      No driver of both versions has ever done better in the MT car. Acceleration wise that is.

      VW have no limit on the number of launches.

      I expect that as in the Golf R world, there will be tuners who offer reprogramming for engine and trans ECU's. Then you can kiss the warranty goodbye.

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      • #33
        Originally posted by Bikerjulio View Post

        My post #14 talked about this a bit. The programming is built into the ECU's by the engineers and they'll provide the best they can within the limits of the drivetrain.

        The current Golf R is a great example because the identical car is available with either a manual or DCT trans. Two things to note:

        No driver of both versions has ever done better in the MT car. Acceleration wise that is.

        VW have no limit on the number of launches.

        I expect that as in the Golf R world, there will be tuners who offer reprogramming for engine and trans ECU's. Then you can kiss the warranty goodbye.
        Thanks for replying. So it’s all in the programming. I know there’s no way a manual trans can beat it. But is there an advantage over say a standard torque converter based auto? I’m assuming there’s more fine tuning, and computer adjustability with the DCT? Or in a straight line/acceleration runs (0-60, 1/4) are the two pretty evenly matched?

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        • #34
          Originally posted by TtiME View Post

          Thanks for replying. So it’s all in the programming. I know there’s no way a manual trans can beat it. But is there an advantage over say a standard torque converter based auto? I’m assuming there’s more fine tuning, and computer adjustability with the DCT? Or in a straight line/acceleration runs (0-60, 1/4) are the two pretty evenly matched?
          I don't see any difference.

          In a stock car with stock tires, traction is going to be the limiting factor. So it's more a battle of traction control systems rather than transmissions.

          And then speed of shift, where I'd think a DCT always has to have an edge.

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          • #35
            Originally posted by TtiME View Post
            But is there an advantage over say a standard torque converter based auto?
            A DCT still has a torque converter, right?

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            • #36
              Originally posted by 73shark View Post

              A DCT still has a torque converter, right?
              not typically. They usually use a wet or dry clutch. Performance based DCT usually are wet.

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              • #37
                Originally posted by 73shark View Post

                A DCT still has a torque converter, right?
                VW/Porsche have had DCT transmissions in production longer than anyone and never used a torque converter. It would add weight and complexity and kind of negate the whole point of having a DCT.

                In past times some manufacturers had problems with stop-start behavior. Which caused some to look at incorporating a lockup TC.

                I daily drive a 2018 Golf R DCT and have had no complaints at all about slow speed issues or anything else for that matter.

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                • #38
                  I think the biggest difference between dct and auto, from a driver perspective, is instantaneous shifting with paddles, as opposed to the delay with auto trans. I test drove the auto GS and in my mind, the paddles are a waste of time.
                  The least we can do is wave to each other

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                  • #39
                    DCT “no no’s” by Jason Fenske of Engineering Explained. While I am have driven a DCT, might as well be using our waiting “down time” to get smarter,” at least learning what I should no do when my DCT arrives. Always always, thank you very much Jason.



                    So many questions about the ME right now; so few answers yet.

                    Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. A ME C8 Corvette is coming next.

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                    • #40
                      Originally posted by Bikerjulio View Post
                      I have a DCT car, a 2018 Golf R. There is a very active Golf R user group with much discussion about the DCT behavior and characteristics. Particularly in auto mode.

                      The key thing to understand is that the "brain" that controls it tries to make a best guess as to what gear it should be in next and sets up the system so that the non-engaged clutch will transfer to that gear when a shift is initiated by the system.

                      It tries to make this guess based on driver input, a big part of which is throttle position. So, a straight acceleration run is easy for the system and the car is slightly faster in auto than in manual mode.

                      Likewise, an even slow down to a stop will result in nice rev-matched sequential downshifts.

                      The downside, and what leads to complaints, is kickdown behavior, when there can be a longer pause, as the system realizes it guessed the next gear "wrongly" and at the same time reduces power while making the shift. Usually this occurs when cruising in a high gear then suddenly nailing the throttle. The trans may have 6th set up as the next gear, when the new throttle input implies 3rd is needed for example.

                      The pause in shifting can be disconcerting, especially compared to the superfast shifting that is the usual case, to the point that people believe the car has a defect. The solution in this case is to downshift manually.
                      This is accurate. But if owners think about a DCT is a manual, that just happens to have an easy mode, then they will drive it like it was meant to be driven.

                      I have to tell people who drive my car all the time, it isn't an automatic, it's a manual that shifts for you. When you think of it like that then BAM! It's an awesome driving experience.

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                      • #41
                        Originally posted by TtiME View Post
                        So a DCT acts like an electronically controlled manual trans correct? So for launching purposes or launch control it can be programmed to hold higher rpms than your standard tc auto and it can slip the clutch (like a manual) to manage the traction on launch? We know it’s faster shifting in a straight line but is it also programmable to launch much more affectively then a standard auto? This could make a lot of sense why Ford went DCT.
                        Yes. Yes. Sort of yes.

                        The last one is tricky. The auto trans is so easy on a drivetrain during a launch compared the manual counterpart. And a normal manual can have a good driver alter the RPM, clutch engagement, etc for different track surfaces....or different tire types. Think about a street tire, a drag radial, and a bias ply slick. In a manual car you launch those tires DRASTICALLY different.

                        The problem with the DCT is the programming can sense the track conditions...but it has no way of knowing that you have fundamentally altered the type of tire and the launch needs to be drastically different.

                        This is why you see even the 900+hp Mclaren 720s's that are chasing 8sec 1/4mi times still running street tires. Putting DR's or BP's on a DCT car can be a nightmare.

                        I completely gutted and redesigned my entire control system on my car to better control the launch. I'm coming from a 335is DCT. Factory 330hp and launch control was fun. But when you are at 700hp the standard factory programmed LC routine was completely useless. So I ripped out the ABS, Stability Control System, DCT Control System, DME, and TCU to put in different components to allow the changes to my LC routine. And it works great on street tires now (like those 720s's), but it's a **** show on BP's.

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                        • #42
                          Originally posted by 73shark View Post
                          And now we know how a DCT works. Thanks for posting.

                          It seems like this is the electro-mechanical equivalent of power shifting only faster and less damaging to the drivetrain.
                          You nailed it. Faster is such an understatement though. These things can shift so fast that it's nearly imperceptible from an acceleration standpoint. There is a sense of continuous uninterrupted acceleration...

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                          • #43
                            I have never driven a DCT (do not like a traditional automatic even with paddles, and have had 53 manual transmission in a row), so I would need to train myself to instantly during those non-linear accelerating and decelerating circumstances, to use my instantly use paddles to direct/place the car into the correct gear for what I am going to do immediately next.

                            Starting to understand this mentally, but clearly going to have learn/practice these behaviors during those circumstances to the point they become instinctive (like driving a manual is to me now).

                            Thank you very much Bikerjulio and Biltmore.
                            So many questions about the ME right now; so few answers yet.

                            Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. A ME C8 Corvette is coming next.

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                            • #44
                              Thanks for the info, very informative.
                              I've never ridden in one or driven one, and to be honest never gave much thought to what it even did/how it worked.
                              Definitely some pros and cons. Thx again.

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