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.
Article comments
1 - Michael Karesh
Perhaps the best explanation of the DSG I've come across. Excellent job.
2 - 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?
3 - Ashleigh
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.
4 - 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?
5 - Ashleigh
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.
6 - 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
7 - 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.
8 - 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.
9 - Ashleigh
Remember most of them are wet clutches, so wear isn't that high.