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DSG: The Future Of The Gearbox

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The VAG Direct Shift Gearbox – sometimes called the S-Tronic in the Audi range – is the world's first production dual clutch semi automatic gearbox. The system was developed for Audi by BorgWarner for use in the companies Audi TT 3.2V6, and was so well received it is now used in much of the Volkswagen Audi Group range.

The DSG is often compared to F1 style automated or robotic manual gearboxes, but differs in some very important ways.

The DSG gearbox is, however, not a new invention. The system was first designed by Andolphe Kégresse just before the second world war but because of the lack of technology, not to mention the war, he never produced a working version of the Dual Clutch Gearbox (DCG). The system was used by another German car company in the 80's though: Porsche used the PDK (Porsche Doppelkupplungs) system in their 956 and 962 Le Mans race cars, and Audi used the same system in the Sport Quatro S1. Porsche and Audi have a long history of technology sharing.

Both of these uses eventually faded, primarily because the computing technology that allows the system to work so effectively did not prove to be reliable enough in the tough and demanding world of the race car.

To understand how revolutionary the DSG gearbox is, first I will explain the F1 style systems. These differ in name depending on the manufacturer; Ferrari call theirs the F1 system, and BMW call theirs the SMG system.

These gearboxes all have one thing in common: they are just manual gearboxes, with a manual clutch that is operated by pneumatics. This method has many of the benefits the DSG box does. The gearbox itself weighs less: as the gear change is accurate, and no human mistakes can be made, the materials can be less hardy. They are also far more performant than the manual equivalent, both the BMW SMG II and the Ferrari F1 systems change cogs in around 80 milliseconds. This means that, while the gear is being shifted, all the power from the engine is waisted and a feeling of on-off-on is felt in the car as the pneumatics shift from in gear, to clutched, and then back into gear. The smoothness of this in the car depends on the software controlling it: for the fastest changes it can feel quite 'bumpy', similar to a bad gear change in a manual car. The only way of releaving this issue in the past was to fit a torque converter, this is the way that a standard auto box does it, and why it feels far smoother than any of the manual gearboxes produced. A torque converter, however, is very wasteful in terms of power, and usually very heavy.

The DSG box takes the basic idea of pneumatic clutched boxes a step further. The heart of the DSG comes from the fact it has two clutches. The basic idea being that the gearbox can then have two gears engaged at any one time, one driving the car, the other waiting to take over.

The clutch arrangement is setup for odds and evens, where clutch 1 operates the 1-3-5 gears and clutch 2 operates 2-4-6.

DSG works by allowing the software to decide what gear the car will need next, and then pre-selects it. If you are accelerating, it will have the next gear up, and likewise if decelerating, the next gear down.

The system can then watch for a change signal – this is either done by clicking the corresponding paddle by the driver, or if in full auto mode the computer – and the gearbox can then tell the currently disengaged clutch (the one driving) to engage, and at the same time tells the engaged clutch (the pre-selected gear) to disengage. In this way the driver and passengers do not experience the on-off-on feeling associated with manual gearboxes. Instead, the gear change feels much more like that of an automatic gearbox.

However, because the change happens so quickly – around 8 milliseconds – the engine can maintain drive and the losses involved in the gear change are much reduced. This can be seen visually in the video below.

The video clearly shows the benefits of the DSG vs a very quick-changing manual driver.

The DSG gearbox is obviously controlled by computer, and this adds other benefits as well, even over race-going Sequential Manual Transmisions.

The computer in the DSG box monitors many of the cars sensors, these can be RPM, speed, angle of steering input, amount of wheel spin, braking and g-forces. It can then use these inputs to make decisions on which gear the car has to be in at any one moment.

For example, if you are approaching a tight corner you may want to change down two or even three gears. The computer sees that you are braking heavily, and that steering input is being applied, and can then change down either more quickly, or skip gears altogether and shift from sixth into third in one step. This allows the driver to keep the RPM in the best range for drivability. Likewise, if driving in snow or mud, the computer sees that there is a lot of wheel spin at low speeds, it can then shift up into a higher gear to allow the wheel spin to be controlled.

The gearbox also keeps the F1 style gearbox's benefits. Because the computer will change gear very precisely, and not over stress the components, the weight of the whole unit is not much more than a conventional gearbox and clutch. This is because the parts can be made to much tighter tolerances, but still manage the same life expectancy as the manual counterparts.

There is a downside to the gearbox though: it cannot be used in races. This is because it changes gear so quickly, and the loss of drive is so minute, that the gearbox gets classed as a Constantly Variable Transmision. The FIA and other governing bodies outlawed this in the early 80s. However, with the speed that some of the current Formula One cars can now change, this may be altered. The current Honda gearbox is called the 'Lossless' gearbox after all, but they did prove that it reduces engine power and its use was therefore allowed.

 The crowning achievement of the DSG is the English-made, Ricardo Company's seven speed DSG, for use in the Bugatti Veyron. That particular car is worthy of its own – more detailed – article, so that will have to wait.

So, next time you drive a DSG car just think: You can change gear faster than even the Formula One and Indy drivers.

Special thanks to Audi for the images and the link to the video demonstrating the gearbox in action.

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  • Sobahi Osama

    good job

  • Jaikumar

    Is there is any video explanation?

  • Luís Pires

    That´s what Germans do best: to use science to develop good products and get money from it (that´s also can be called engineering).

  • Adam

    In addition to extending the warranty on the DSG transmission to 100K miles, VW has replaced the mechatronic units in most of the faulty units! Mine,in my R32,Is a fantastic transmission! It’s almost like mind control, when I want something to happen it magically does!!
    Have fun safely!! 🙂

  • Kev

    Some of the comments above do not apply to current dsg boxes. For example, when stationary with the footbrake applied, the clutches disengage completely and so there is no ‘drag’ on the clutch at all. If you apply the handbrake and take your foot off the footbrake – then the clutches re-engage and the car will try to pull forward. Clearly this is not good and so, when stationary, say at traffic lights, either keep the footbrake on or, if you want apply the handbrake on its own – just slip the box into neutral. My previous four cars have been conventional autos. I have recently bought a Golf 1.4 TSi with the DSG box and it is superb. There are a few minor differences that you have to get used to – but changes are incredibly smooth and seamless and, unlike with conventional autos, there is no fuel or performance penalty at all with the latest dry-clutch DSGs. In fact there are YouTube videos demonstrating that 0-60 times with identical cars, one manual and one DSG, are faster with the DSG box. No manual driver can change gear as fast as a computer controlled DSG can!

  • mark mccaffrey

    Your comments are great about the DSG box. But i find so many negative reviews on other web pages. Is its reliability good or poor? I am going to buy the new Sharan later this year and am considering the DSG box, would it be a good choise for me. It will be my wifes car doing 7500 miles per year average mostly the school runs and shopping runs. we plan to keep it for around 6 years. Will the DSG stick short runs and last with out fault for around 45000 to 50000 miles. If you read other reports this is questionable.Are the justified in their comments?

  • Nik Palekar

    Why are there so many problems with the DSG slipping into neutral and sometimes refusing to engage into ‘D’rive mode. NHTSA in the US has forced VW to extend warranty to 10 years upto model year 2009. Is the 2010 model of the DSG improved?

  • Remember most of them are wet clutches, so wear isn’t that high.

  • Federico Melo

    I just bought a 2.0 T FSI with DSG and realized about the charge being applied though odd clutch when standing stop in drive mode and can’t believe it. Besides the obvious feeling, I checked it by watching instant fuel consumption increasing when switching from neutral to drive or first. I only can think that wear is so low that VAG group thinks is better, because it would be extremely easy to fully release clutch when detects speed zero and brake applied. Even if they assured that wear is minimal I would prefer full release and I think I’ll get use to place it into neutral while waiting for light or traffic to move.

  • LT

    That’s correct, it’s basically the same as when manual car drivers slip it during a hill start etc. Obviously the car can use it’s brakes etc to compensate so the wear is actualy lower than conventional clutch.
    I doubt the wear is lower since either car can use the brakes. The difference is in a manual transmission the driver disengages the clutch. With a dsg when stopped at traffic lights for example the clutch is still dragging and you can feel this as the load is eliminated if you shift to neutral. It will be interesting to see just how long the clutch lasts in a dsg compared to an experienced driver with a conventional transmission.

  • lawrence ogden

    the dsg box is brilliant i have a glof tdi 170 dsg and can get 54 mpg on a run (19km/litre) it is the best auto box ever put in a car the gearchange is seamless dont bother using the paddles put it into drive and enjoy the ride if you use sport mode it holds on to 5th gear to 115 mph.tdi170gsg is one of vw`s best kept secrets

  • It’s mostly down to the extra weight of the DSG ‘wet’ box. The newer dry clutch boxes should get the penalty down a bit more.

    However manufacturers figures are for an ideal manual driver, and the DSG is always going to perform the same, so in reality the difference is negligible at best.

  • Carl

    Thank you for a very helpful article. However, when I read the published mpg figures (here in the UK) there seems to be an up to 10% fuel consumption penalty associated with a DSG gearbox. Granted that’s better than the apparent 15-20% of a traditional automatic. But why the apparent 10% penalty?

  • That’s correct, it’s basically the same as when manual car drivers slip it during a hill start etc. Obviously the car can use it’s brakes etc to compensate so the wear is actualy lower than conventional clutch.

    The DSG is being re-invented soon as well. VW have announced a 7 speed, dry clutch system capable of handleing 450ft/lb torque that will be launched soon.

  • Tony

    Very good article, but still haven’t seen explanation on how DSG operates from standing start – Electronic controlled engagement of conventional clutch in first gear? Does this mean clutch is being continuously ‘slipped’ when in Drive but at standstill with brakes on? Does this not lead to increased clutch wear for the clutch that includes first gear?

  • Perhaps the best explanation of the DSG I’ve come across. Excellent job.