There's no denying that cars are complex creations. Thousands of small, dedicated parts need to work in unison to make the vehicle behave the way that it is intended. The internal combustion engine has hundreds of moving parts, and their actions need to be timed perfectly to create power to propel you forward. The gearbox is a crucial part of this forward propulsion and has many moving parts that need to be controlled. The dual-clutch gearbox takes away some of the manual intervention required to make it do so, but what does this mean to you?
Related: Manual vs. Automatic Transmission - Which is best?
A gearbox's purpose is to reduce (or increase) the number of engine crankshaft rotations sent to the wheels. As the internal combustion engine has an optimal operating range, it is necessary to alter the number of revolutions that are transferred to the wheels when it starts to exceed these parameters. In this way, it is possible to continue accelerating forward while keeping the engine in this sweet spot. Before you can understand the benefits of a dual-clutch gearbox, you need to know a little more about how gearboxes work in general.
The manual gearbox
South Africans are most familiar with the manual gearbox. This gearbox requires that the driver physically changes the gears themselves using a clutch pedal to disengage the clutch, freeing the gears from the engine, selecting the necessary gear using a gear lever, and then releasing the clutch to join the engine to the gears again and allowing the power to be transferred to the wheels. This process is repeated numerous times as the driver accelerates and decelerates.
The clutch is a coupling that allows the power to be transferred to the gearbox (and in turn, the wheels) and allows for the disengagement of the engine and gearbox to make changing gears easier and less damaging to the rotating components. It consists of friction material on a disc sandwiched between the flywheel and a pressure plate.
A traditional automatic
An automatic gearbox performs the same duties as a manual gearbox in that it allows the engine to remain in its peak operating window, but does away with the driver's involvement in the process. Constructed slightly differently from a manual gearbox, an automatic will use a series of planetary gears to adjust the ratio of revolutions sent to the wheels. It is coupled to the engine with a torque converter; comprising two discs with vanes on them and suspended in oil. As the rotational forces increase, the oil spins and transfers the rotation energy to the gearbox side, spinning that disc. Think of it as two fans facing each other. Switch one on and the air being pushed towards the fan that is off, will cause its blades to start spinning even though it's not receiving any power.
The dual-clutch gearbox
The dual-clutch gearbox combined the mechanical actions of a manual gearbox with the self-shifting convenience of an automatic. As such, a dual-clutch gearbox can be operated in a similar manner; you can leave it to change gears on its own or you can select the gears yourself, usually with steering wheel-mounted paddles.
The gearbox internals are rather similar to those of a manual gearbox but instead of having a single clutch, two clutches are used. These concentric clutch discs are matched to either the even-numbered gears (2, 4, 6 etc) or the odd-numbered gears (1, 3, 5, 7 etc) and this allows for preselection. As the gearbox shifts from one gear to the next, the clutches simply trade places, the engaged one disengaging as the other one engages. This allows for a quick and near-seamless change of the gears from one to the next. While one gear is selected and in use, the next gear is made available and put on standby for this change. This helps cut down the change time and helps improve performance and efficiency.
A computer controller allows the gears to change on their own but also allows for the driver to select the gears themselves, should they wish to do so. It's for this reason that many performance-orientated cars have opted for a dual-clutch system so that the vehicle is easy to drive in traffic but can still be driven in a spirited manner with the driver able to choose which gear they would like to be in.
Dual-clutch gearboxes go by many names, depending on which manufacturer is using them. Volkswagen calls them DSG while Renault calls them EDC gearboxes. Porsche uses the acronym PDK. You can find out how to drive one here: How to: Drive a semi-automatic car
