The gears are split across the split input shaft by odds and evens, allowing the transmission to switch back and forth between them as the car accelerates and decelerates – pre-selecting each gear on the opposite input shaft to the one engaged. However, the input shaft connected to both the clutches is not one shaft, but two - with one of them sitting within the other and allowing each clutch to contact and act upon a different one. The twin clutches are arranged concentrically – meaning one sits within the circumference of the other, crucially enabling them to both work on the same input shaft. Yes, there are two clutches, but simply having an extra clutch doesn’t really explain how a transmission can select more than one gear at a time. The clue is in the name but that’s only describing part of the process. Unless you’re already familiar with how a DCT works, you’re probably already questioning how this type of transmission can have two different gears selected simultaneously without exploding into a shower of shrapnel. This allows the computer to have the predicted gear already engaged before the change is made. How it achieves these lightning fast changes is by anticipating what the next gear needed will be, based on factors such as rate of acceleration or deceleration, current speed of travel and engine speed.
#7 DCT TRANSMISSION DRIVER#
Gear changes on DCTs can now be measured in the milliseconds, faster than any driver is capable of, and still retain the advantages a manual gearbox has over an automatic. The less time spent off the power changing gear during acceleration the faster the vehicle can accelerate - and by reducing the time spent off the power during gear changes in general, the better fuel economy will be as engine power isn’t wasted.
The purpose behind a DCT is to reduce the gap between gear shifts to a minimum, with the benefits being improved performance and fuel efficiency. It wasn’t until 2003 that a production road car featured a DCT, in Volkswagen’s Mk4 Golf R32. The electronics needed for the computerised control module had not yet reached the miniaturisation levels of modern times and so were quite sizeable and took up valuable engine bay space. Space was also a considerable restriction. The Porsche 956 released in 1983 received the distinction of being the first to feature one, and their complexity and expense kept them in the realm of motor racing and high-end super cars for the most part. Its realisation had to wait until the 80’s, and it was Porsche who eventually became the first major adopter having worked on their own version since the 60’s. Like so many ‘new’ developments for automobiles, the double clutch transmission is an idea that had been around for a significant amount of time before finally being put to use, having been experimented with pre-World War two. ORIGINSĪlso referred to as a Direct Shift Gearbox (DSG), most car manufacturers have their own version or versions, but use them selectively across their ranges of vehicles – with the Volkswagen group the most invested in their implementation. Sitting in the middle ground between an automatic and a manual transmission, the simplest way of describing their operation, is that they’re an automatically operated manual transmission – achieved by using two clutches.ĭoing away with the torque converter of a normal automatic transmission, they utilise the traditional gearing methods of a manual - but then split that gearing across two output shafts to allow power flow to shift between them incredibly quickly.
#7 DCT TRANSMISSION DRIVERS#
Despite what is undoubtably very clever and complex engineering, the Double (or Dual) Clutch Transmission (DCT), has a mixed reputation with drivers and has not achieved the level of ubiquity many thought it would.
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