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 though 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.
Fuel consumption* of the Boxster Spyder: Urban: l/100 km -; Extra urban: l/100 km -; Combined: l/100 km -; Emissions: g/km -.
* These data were obtained using the Euro 5 measurement method (715/2007/EC and 692/2008/EC) in the NEDC (New European Driving Cycle) with standard equipment. The information does not refer to an individual vehicle and is not part of the offer, but is simply provided so that comparisons can be made between different types of vehicle. Further, up to date information on the individual vehicles can be obtained from your Porsche Centre.
Consumption figures were obtained on the basis of standard equipment. Special equipment may affect consumption and performance.