DSG / S-Tronic / TCT Gearbox
TCT (Twin Clutch Transmission) or more commonly know in in VAG vehicles as DSG (Direct Shift Gearbox) is a 6/7 speed automatic gearbox with two clutches.
From a technical point of view, the device consists of two gearboxes in parallel, each with its own clutch, which allows the selection and engagement of the next gear while the previous one is still engaged. Shifting is simply obtained by gradually switching the corresponding clutches, guaranteeing continuous torque delivery and therefore traction.
The electronic transmission control unit, sensors and hydraulic control unit form one compact unit. The control unit uses information such as engine speed, road speed, accelerator position and driving mode to select the optimum gear and to determine the ideal shift point. The control unit then implements the shift commands in a sequence of precisely co-ordinated actions. Each change takes less than four-hundredths of a second. DSG can be used manually, via the Tiptronic gearlever or the optional paddle shifts.
Multitronic / CVT Gearbox
The name multitronic stands for the new variable automatic gearbox developed by VAG Group. The variable automatic gearbox is commonly known as the CVT gearbox. CVT is the English abbreviation for Continuously Variable Transmission
The key component part of the multitronic is the variator. It allows reduction ratios to be adjusted continuously between the starting torque multiplication ratio and the final torque multiplication ratio. As a result, a suitable ratio is always available. The engine can always operate within the optimum speed range regardless of whether it is optimised for performance or fuel economy.
The variator comprises two tapered disc pairs - a set of primary pulleys (pulley set 1) and a set of secondary pulleys (pulley set 2) - as well as a special chain which runs in the V-shaped gap between the two tapered pulley pairs. The chain acts as a power transmission element.
Pulley set 1 is driven by the engine by means of an auxiliary reduction gear step. Engine torque is transmitted via the chain to pulley set 2 and from here to the final drive. One of the tapered pulleys in each of the sets of pulleys can be shifted on the shaft for variable adjustment of the chain track diameter and transmission ratio.
The two sets of pulleys must be adjusted simultaneously so that the chain is always taut and the disc contact pressure is sufficient for transmission purposes.