THE PORSCHE DOPPELKUPPLUNG
Stuttgart, April 11, 2013.- We’ve come full circle. In den 1980s, Porsche developed a world first in automotive technology for use in races and thus won the race: the dual-clutch transmission. In 2013, this progressive transmission technology returns to the circuit course: The new 911 GT3 has the fastest and most powerful Porsche dual-clutch transmission – PDK in short – that Porsche uses for a production vehicle. Just under 30 years – starting with a long pause and ending in an incredible success story. Depending on the model range, more than three-quarters of all Porsche vehicles today are delivered with PDK – and the trend is on the rise.
With 54 victories and numerous championships, the Porsche 962 that was used in races starting in 1984 is probably one of the most successful racing sports cars of all time. The Porsche dual-clutch transmission was first developed for the 962. The gearbox construction stood the test in the long-distance world championship. It was not developed for standard production at that time because the electronics and the computer capacities were not yet fully mature technically to meet the high comfort standards for operation in a road vehicle.
2008: first PDK for sports cars in the 911 Carrera
With progress made in the development of control electronics, this changed after the new millennium was hailed in. Porsche took up the development again and presented the first dual-clutch transmission for production sports cars in the 911 Carrera in 2008. It replaced the conventional Tiptronic S automatic gearbox and has been perfectly custom-fit for the sports cars: The Porsche Doppelkupplung combines dynamic driving performance and the excellent mechanical efficiency of a manual transmission with the great shift and driving comfort of an automatic gearbox. Right from the beginning, the PDK was able to shift gears up to 60% faster than an automatic gearbox. It facilitated gear shifts without any interruptions in propulsive power and reduced fuel consumption.
The PDK gears are divided into two half gearboxes connected to the engine through two parallel powershift clutches. The odd-numbered gears and reverse gear are connected to clutch I – this package is the first half gearbox. Clutch II engages the even-numbered gears, making for the second half gearbox. In principle, the individual gears are selected via shift forks as in a mechanical manual transmission, which are activated electro-hydraulically, however, in the PDK. Gears one to six are designed for a sporty performance – the vehicles reach top speed in the sixth gear. The seventh gear has a long gear ratio for saving fuel.
The PDK was greeted by customers with praise from the very onset. One year after the 911 Carrera received the new gearbox as an option, it was also optionally installed in the Boxster and Cayman. When the Panamera had its world premiere in 2009, all three starting models were already equipped with the dual-clutch transmission as standard. Although the PDK works the same in all three model ranges, it’s a specific development for each of the three model families due to the fact alone that they feature three different drive systems.
2013: comeback of the PDK in the 911 GT3 able to meet the needs of the circuit course
With the new 911 GT3, the capabilities of the PDK have reached a new level. Our motorsports engineers have thoroughly reworked the dual-clutch transmission mechanically and in terms of controls especially for the high-performance sports car. The result is a transmission that offers the driver all the features that count for driving performance taken over from the previous manual transmission, augmented by the performance advantages of the PDK. Thus it can be driven on circuit courses like a sequential gearbox – with even more potential and emotional driving fun.
“Lightning shifts” with extremely short response and shift times
Shift strategy and response time of the PDK in the 911 GT3 have been systematically developed for performance and are fundamentally different from those of other Porsche sports cars. The driver can feel it especially with manual upshifts in the form of a “lightning shift”: Response times of under 100 milliseconds are possible. For boosting the driving performance, the lightning shifts are done with a torque increase, and the gear shifts are translated with a highly dynamic adjustment of the engine revs to the newly selected gear. Shift times are in ranges that were reserved to motor sports up to now.
Paddle neutral: decoupling function with the PDK of the 911 GT3
The driving performance of a sports car driven for optimal lap times is also determined by the clutch. Hence the PDK in the 911 GT3 has a “paddle neutral” function. If the driver pulls both shift paddles concurrently, the clutches of the PDK are opened and the force flow between engine and powertrain is interrupted. If both shift paddles are released again, the clutch closes with lightning speed when the PSM is switched off. If the PSM is activated, the clutch also closes quickly but not so pulse-like.
This function essentially offers two advantages: If the vehicle understeers, for instance on a wet road in a curve, the driver can neutralise by pulling the paddles, thus building up additional cornering force on the rear axle wheels. The second aspect refers to influencing the driving dynamics individually through the pulse-like onset of the drive power when coupling. Comparable to a traditional clutch in conjunction with a manual transmission, the rear of the vehicle can be consciously destabilised when turning.
Adaptive gear shifting with sporty strategies
The PDK offers the driver of the new 911 GT3 the alternative of leaving the shifting to the adaptive transmission control. Basically, the DSG of the new 911 GT3 has only two shifting strategies: Sports and Race Track. With them, the gear shifts in the new 911 GT3 are always quick. Shift processes and shift points get their bearings from the driving dynamics of the driver. In the Race Track mode, the PDK follows shift maps that are tailored to the requirements of pure circuit course operation. The gears are held longer and upshifts are carried out only with higher torques. The circuit course alignment also means that the shift program remains performance-oriented even with a moderately sporty driving style. Thus the high-performance sports car always moves within performance-driven operating points, and an increased propulsive power potential is available at every moment without the driver having to shift gears.
Shorter gear ratios: faster times on the Nürburgring Northern Loop
The mechanical changes of the 911 GT3-PDK in comparison to the dual-clutch transmissions in the other Porsche models affect mainly their internal structure. By using lighter gear wheels and gear sets, the torque dynamism of the high-torque engine is optimally supported. Moreover, the total weight of the PDK was reduced by two kilogrammes. Shorter gear ratios result in an entirely new characteristic; the 911 GT3 reaches top speed in the seventh and highest gear. In conjunction with the rear axle ratio that was shortened by 15%, the new 911 GT3 features significantly shorter total ratios in all gears than the 911 Carrera models.
As a result, the driving performance of the new 911 GT3 again sets records. Two values in particular are influenced by the PDK: With full acceleration, the 911 GT3 reaches the 100 km/h mark in 3.5 seconds and accelerates to 200 in less than twelve seconds. And the new 911 GT3 masters the Nürburgring Northern Loop, the admittedly most difficult race course in the world, in under 7 minutes and 30 seconds.
More information:
Text and photograph by: Porsche.
