A Direct-shift gearbox most commonly known as DSG is a dual clutch unit which is controlled electronically. It is a manual gearbox having multiple shafts in transaxle design having no conventional clutch pedal. In layman terms, DSG is a pair of manual gearboxes and clutches which are contained in one housing and work as a single unit. DSG was first designed by BorgWarner. Moreover, it was licensed to Volkswagen Group initially. DSG has a unique tendency to achieve faster shift times by using a couple of independent clutches
The Direct Shift Gearbox conventionally uses a transmission shift lever which is floor mounted and is quite similar to a conventional automatic transmission. The lever is operated in a straight plane. An additional button is also used to prevent an inadvertent selection of an inappropriate shift lever position.
How DSG works?
The Direct Shift Gearbox is a unique two-in-one concept. It is available in both 6-speed and 7-speed versions. In DSG, the two same electronically controlled shafts manage the gear selection and always anticipate your next shift.
When the engine is turned on and drive mode is selected, one shaft selects first gear and the second shaft puts the next gear on stand-by mode. When the gear changes to second then the second shaft is engaged by making the first shaft put the third gear on standby. DSG gives the option of two driving modes i.e. normal and sport. Direct Shift Gearbox is proved to be more efficient than conventional automatic transmission. DSG gearboxes are available in 6 and 7 speed variants. Both the gearboxes of DSG are application- specific. The 6-speed is coupled with high torque engines whereas the 7-speed variant is more efficient when combined with smaller engines having torque output of up to 250Nm.
Merits and demerits
DSG has many merits and some demerits as well.
Merits of Direct Shift Gearbox:
Smooth and easy gear shift operations.
During gear shifts, no torque transmission loss from the engine to the driving wheels.
Improved fuel economy (up to 15%) than conventional automatic transmissions.
Consistent down-shift time and short up-shift time.
Demerits of Direct Shift Gearbox:
Marginally poorer mechanical efficiency as compared to conventional manual transmissions
Comparatively costlier transmission fluids or lubricants with the requirement of dedicated additives.
Comparatively expensive to manufacture and thereby, increasing new vehicle purchase price.
It is heavier than Getrag conventional manual transmission.
Pictures source : Autoevolution