Volkswagen Automatic Gearboxes: Dual-Clutch Transmission (DSG)
Volkswagen has been something of a leader in the development of transmission technology, further aided by their corporate union with brands such as Audi whose “Vorsprung durch Technik” motto (Advancement through Technology) has long led to incredible developments and advancements.
Perhaps VW’s proudest creation to date is that of the so-called “Direct-Shift Gearbox” or DSG gearbox for short. This dual-clutch transmission unit has helped to close the gap on automatic and manual cars so much that now even top-end luxury sports car brands are starting to favour it over any automatic option. In today’s blog, we’re creating a detailed profile of this incredible dual-clutch unit and how it has helped to change everything in the automotive world.
What is a DSG Transmission?
Don’t be confused by the abbreviations. You might see “DCT” — or dual-clutch transmission — as the abbreviation used on most OEM dual-clutch setups, but on a VW car, it will be “DSG” — direct-shift gearbox — just to be clear. While in principle these units share many similarities, the VW DSG is still fairly unique, though in the simplest terms it is still two electronically controlled separate manual transmissions that are built into a single unit.
The chief idea behind the DSG is to provide a manual-like level of control and efficiency but with the ease and convenience of an automatic transmission. To that end, DSG units are built to offer a degree of flexibility when it comes to controlling how gear shifts operate.
How Does the DSG Work?
As the name of the concept “dual-clutch transmission” suggests, the DSG works by using a pair of interwoven clutch packs, and two separate input shafts. The first of the two clutch packs manages the odd gears; 1, 3, 5, and 7 while the second clutch pack manages the even gear ratios; 2, 4, and 6. If you talk to a mechanic about these clutch packs, they may refer to them as K1 and K2.
One of the most important characteristics of the Volkswagen DSG design is the transaxle build. This means that inside the main transmission case is housed the gears, differential, and final drive all in one. The inner workings of the unit include a flywheel, which connects to the transmission’s input shaft, which is then engaged by the clutch packs. The process takes power from the engine, sending it through the transmission housing and to the wheels.
In case you were wondering, the majority of DSG units employ what is known as a “wet clutch” design, which means that the friction rings and connected plates are entirely covered in transmission fluid both for lubrication and for cooling. As for their control, it’s part of an electronically controlled system known as the Mechatronic unit, a component that some call the brain or heart of the entire DSG system.
Using its connections to various sensors, the ECU, the CAN bus system and more, the Mechatronic unit is capable of pre-selecting the next gear before it even needs to be engaged, which is how the DSG is able to offer such smooth and seamless shifting even in its automatic mode. It is through gathering all the salient data from each system that it knows with remarkable accuracy which gear will be required next, regardless if you’re taking a hard corner at speed in the country, or your trundling along in heavy city traffic.
Does the DSG Work as Well as VW Claims?
Volkswagen has made big claims about their direct-shift gearbox unit, most importantly that it helps to narrow the gaps between manual and automatic transmission vehicles. For so many years, the biggest drawback of any automatic car was that there was typically lag between gear shifts, which in turn impacts performance. It was a lot easier, for instance, for a good driver to get a manual car up to a strong acceleration in time for merging with a motorway than it was for a driver of an automatic car.
VW’s claims are not poorly founded. In fact, their DSG Mk7 GTI unit has been recorded as being capable of completing shifts around 200 milliseconds faster than the best drivers can manage in a manual car. Therefore, when compared to the average driver, we’re looking at something very special indeed. Strong drivers found that when accelerating up to 60-mph, the DSG allowed them to shave off about 0.2 seconds (200 milliseconds) off the acceleration time, moving it from 6.0 to 5.8 seconds. Over the quarter mile, those same results were found, dropping from 14.3 seconds from 14.5.
What is DSG Sport Mode?
Owners of a VW car with the DSG transmission can drive in fully automatic mode, or they can use semi-automatic mode where they can shift gear ratios manually using paddle shifters. The latter provides a more dynamic way to shift gears, and is ideal for those looking for a more manual-like dynamic on the road.
The DSG models invariably come with an additional “Sport” mode, which alters the programming governing the Mechatronic unit. In short, it makes the dynamics a lot more aggressive, but might also take away a little of the fuel efficiency at the same time, if that’s something you worry about. “Sport” mode allows for even faster shifting, and it holds gears longer, while also making use of engine-braking when performing downshifts.
Sport mode can add further differences to the driving experience depending on the model you drive. There are some DSG sport modes that also harden the suspension or alter the responsiveness of the engine, all in the aid of a more athletic and exciting on-road experience.
Is the DSG Worth the Added Cost?
Having the latest DSG model in a Volkswagen car does add to the cost, but one must also consider the benefits of having it. This advanced unit essentially helps to remove the need for a simple binary choice of automatic or manual. The main idea is that the DSG is able to provide one with the “best of both worlds” kind of situation.
With gear shifts sped up, acceleration and on-road dynamics improved, and the flexibility to switch between fully- and semi-automatic modes, this is a unit that can offer universal attractiveness to all drivers.