Porsche Doppelkupplung (PDK)
The optional Porsche Doppelkupplung (PDK), with both manual gearshift and an automatic mode, enables smooth gear changes with no interruption in the flow of power. This results in significantly faster acceleration and lower fuel consumption, without having to sacrifice the ease of automatic transmission.
In total, PDK has seven gears at its disposal. Gears 1 to 6 have a sports ratio and top speed is reached in 6th gear. The 7th gear has a long ratio and helps to reduce fuel consumption even further.
PDK is essentially two half gearboxes in one and thus requires two clutches – designed as a double wet clutch transmission.
This double clutch provides an alternating, non-positive connection between the two half gearboxes and the engine by means of two separate input shafts (input shaft 1 is nested inside the hollowed- out input shaft 2).
The flow of power from the engine is only ever transmitted through one half gearbox and one clutch at a time, while the next gear is preselected in the second half gearbox. During a gear change, therefore, a conventional shift no longer takes place. Instead, one clutch simply opens and the other closes at the same time. Gear changes can therefore take place within milliseconds.
Clutch 1 controls the first half gearbox, which contains the odd gears (1, 3, 5, 7) and reverse. Clutch 2 controls the second, which contains the even gears (2, 4, 6).
The crankshaft transmits engine torque to the dual-mass flywheel which is then channelled through the clutch housing and onto the multi-plate clutches, or to be more precise, the outer disc carrier.
Under oil pressure, clutch 1 closes and forms a frictional connection with input shaft 1. The torque is now transmitted through the first half gearbox – and then the differential – to the rear axle. At this stage, PDK has already preselected the next gear in the second half gearbox. Engine torque is already acting on the other outer disc carrier and, in response to a gear change signal, the overlap shift is initiated, i.e. as clutch 1 opens, clutch 2 closes. The non-positive connection with input shaft 2 is established, and power is transmitted to the wheels. The gear which is engaged is displayed on the instrument cluster. Depending on the gearshift programme, the gear change is optimised for comfort or for sporty handling and takes place in a matter of milliseconds.
The advantage over a fully manual transmission is the considerably faster rate of acceleration for the same rate of fuel consumption. The advantage over a fully automatic transmission is the perceptible increase in driving dynamics – with a similar level of comfort, and a distinct reduction in fuel consumption.
The compact dimensions of the gearbox reduce rotational masses which means a more direct engine response, and the system is more lightweight.
This, along with the long-ratio 7th gear, helps to achieve reduced fuel consumption and emission figures comparable with those of a manual gearbox.
With the optional Sport Chrono Package, PDK is enhanced by the ‘Launch Control’ and ‘motorsport-derived gearshift strategy’ functions.
In essence, PDK combines sportiness with efficiency and comfort. What does all this mean for you? Uninterrupted driving pleasure.
This three-spoke sports steering wheel for PDK has two ergonomic switches.
One press with the thumb and the PDK shifts up. One pull with the index finger and the PDK shifts down. Either the right or left hand can be used.
The gear selector for PDK impresses not only with its unique design, but above all with its superior functionality enabling you to change gear manually. The control concept mirrors the logic of the switches on the sports steering wheel for PDK – press forwards to shift up, pull backwards to shift down.
Even if the gear selector is set to automatic mode, you can still change gear manually using the switches on the steering wheel.
source
http://www.porsche.com/microsite/technology/default.aspx?pool=uk&ShowSingleTechterm=PTPDopKuGe&Category=&Model=&SearchedString=&SelectedVariant=PMTBoxsterAll