Dual-clutch transmissions (DCTs) were a great success after Volkswagen first introduced one in the Golf R32 in 2003.
To date, VW has produced more than 26 million Direct Gearboxes (DSGs), and it is not alone. Previously, the standard had always been the automatic gearbox of the torque converter (slush) and, in a few small cars, perhaps a continuously variable transmission (CVT) that ground teeth horribly.
DCTs are fun to use because they change gears without the engine interrupting torque. In a conventional manual gearbox, the disengagement interrupts the torque to disengage each gear and engage the next. The torque is reset by closing the clutch again and opening the throttle.
In a DCT, each clutch is assigned to approximately half of the gears. So, for example, while the first gear is engaged and driven through “clutch one”, the second gear is preselected through “clutch two”, which remains open. When the driver selects the second gear, clutch one opens and clutch two closes, occupying the drive simultaneously without interrupting the torque. And so on.
Software algorithms control things and try to predict the next movement of the driver by preselecting the next gear. Therefore, if an upshift has been preselected and the driver decides to overtake and it is necessary to downshift, the gearbox will try to predict it.
VW may have been the first company to launch DCTs in large quantities with its DSG, but it wasnt the first to launch them. Neither Porsche nor Audi had the delightfully named Porsche Doppelkupplungsgetriebe (PDK), which adorned the 956 and 962 racing cars and the Sport Quattro S1 rally car.
No, the first working prototype DCT was developed at Leamington Spa by Automotive Products in 1980 and called the hot shift automatic gearbox. The concept may have been hampered by the snail rhythm electronics, but the name was excellent. Conventional gearboxes of torque converters are not as suitable for small engines, and especially were not then, when the power consumption of a torque converter was relatively high – and thats what drove the idea.