3.5 Gearshift strategies and shifting times

General

In addition to the short gear ratios and the short actuation travel of the shift paddles, Porsche Doppelkupplung (PDK) is characterized above all by its unique gearshift strategies and its short response and shifting times (including “lightning shifts”). These characteristics ensure a performance-oriented gearshift behavior with particularly sporty gear changes. The most important driving functions of the Porsche Doppelkupplung (PDK) are based on the strategies of the current 911 Carrera models. For differentiation and in order to adapt to the particularly sporty character of the new 911 GT3, new functions have been introduced and modified functions and specific fine-tuning measures implemented.

The following main development objectives were taken into account here:

• Increasing performance • Reducing complexity • Improving interaction between driver and vehicle • Enhancing emotionality

Increased performance is achieved with the following features:

• Lightning shifts with very short response and shifting times • Performance-oriented adaptation of gear preselection

Reduced complexity is achieved with the following features:

• No special functions, such as Coasting, Auto Start Stop, ECO upshifts • Two driving modes: SPORT (basic setting) and “PDK SPORT” • Special functions, such as Launch Control, are available irrespective of driving mode • No kickdown

Increased interaction between driver and vehicle is achieved with the following features:

• Selector-lever position “M” as an uncompromisingly manual shift function • “M” with no automatic shift functions • “M” with maximum acceptance of gearshift commands even during extreme engine speed-oriented driving • “Paddle Neutral” with additional function based on a conventional clutch pedal

Enhanced emotionality is achieved with the following features:

• Adaptation of the basic gearshift strategy to performance-oriented driving dynamics without additional actuation of driving mode buttons • Adaptation of the one-touch direction on the selector lever to motor sports • Possibility of driving off with increased wheel slip with “Paddle Neutral” • Possibility of influencing driving dynamics individually with “Paddle Neutral” • No crawling without pressing the accelerator pedal Power transmission 3

Power transmission 3

The PDK transmission in the new 911 GT3 essentially has the two gearshift strategies “SPORT” and “PDK SPORT”. Here, SPORT mode is the basic setting and is available immediately after starting the engine without pressing a button. PDK SPORT mode is activated by pressing the “PDK SPORT” button in the center console. In this mode, the shift sequences for changing gear are accomplished with torque increases and maximum performance-oriented gearshift behavior.

Even at its basic setting, the new 911 GT3 has a sporty gearshift strategy. The basic characteristics of this strategy are the same as the “SPORT” gearshift strategy of the current 911 Carrera models. For the new 911 GT3, however, map-specific adjustments were made to the gearshift strategy in order to meet the specific performance requirements, including short gear ratios, as well as the unique engine and vehicle characteristics. As a result, gear changes are always fast.

Based on the current 911 Carrera models, the shift sequences and shift points in shift program “D” in the PDK used on the new 911 GT3 are also adapted and adjusted to suit driver-specific handling. This means that the engine speeds are increased early for changing gear, even for a moderately sporty driving style in performance-oriented rpm ranges (> 3,500 rpm). Engine speeds are increased further for high-performance driving. This is possible because the engine in the new 911 GT3 is exceptionally lively. For the driver, this gearshift strategy - even in the sporty basic setting in “D” - ensures exceptionally good adaptation to the desired driving profile.

PDK SPORT mode

An even sportier PDK mode is activated by pressing the “PDK SPORT” button in the center console. In this mode, the PDK has modified shift maps in selector-lever position “D” which have been adapted to meet the requirements associated with driving the vehicle on race circuits. As a result of the change in the shifting characteristic curves, the shift map is moved towards higher engine speeds. This means that the engaged gear is held longer and the next-higher gear is only selected at higher engine speeds.

Race circuit tuning does not allow “back-adaptation” of the shift map for a moderately sporty driving style in PDK SPORT mode. As a result, a higher tractive force potential is available at all times, without changing gear. If the driver requests maximum acceleration (full throttle up to the rev limit) in PDK SPORT mode, engine interventions are prevented during an upshift for a sporty, comfortable gear change. This means that the engine is operated at full power even during the gear change and as a result, the dynamic torque enhancement during gear changes is once again noticeably reinforced.

Gears available

SPORT (basic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7 PDK SPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7

Automatic upshift and downshift in M

Partial load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .no Full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .no One-touch shifting (selector lever) . . . . . . . . . . . . . . . .front - /rear + (motor sport)

Shifting gears in D

Gearshifts

SPORT (basic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .performance-oriented PDK SPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .performance-oriented

Adaptation to driving style

SPORT (basic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .yes PDK SPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .yes

Moving off

From stationary (without accelerator pedal) . . . . . . . . . . . . . . . . . . . . .no crawling

Launch Control

SPORT (basic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .yes PDK SPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .yes ESC+ TC OFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .active

With all these changes, the new 911 GT3 thus has a PDK transmission with a very high shifting performance and exceptionally emotive gearshift and gear change functions. TC: Traction Control ESC: Electronic Stability Control

Power transmission 3

Power transmission 3

The new 911 GT3 has a much higher shifting performance mainly thanks to its much shorter response times and shifting times as well as lightning shifts with much faster gear changes. The diagram below shows the engine speed characteristic during gear changes as a function of time. The red line in the diagram below represents the PDK shift function of the 991 GT3, while the blue line represents the PDK shift function of the 991 Carrera.

1 - PDK response time - 911 GT3 (991) 2 - PDK response time - 911 Carrera (991)

The difference between (2) and (1) shows how much the shifting time has been reduced.

PDK comparison 03_03_14

3 - Shortening of the response time as a result of functional measures in the Porsche

Doppelkupplung (PDK) (“lightning shift”) 4 - Increase in engine speed gradient as a result of functional measures in the engine electronics (DME) and optimized communication between engine and transmission 5 - 1st gear 6 - 2nd gear

On the new 911 GT3, gear changes for a manually initiated upshift are accomplished by way of a “lightning shift” with very short response and shifting times. This function is initiated using a one-touch switch on the selector lever (M gate) or using the shift paddles on the steering wheel. As a result, gear changes on the new 911 GT3 are approximately 60% faster than on the 911 Carrera models. This is achieved thanks to maximum performance in filling the clutch-specific hydraulic system and by activating the overlap function between the closing and opening clutches at precisely the right time.

The implementation of a lightning shift is the result of years of experience with the Porsche Doppelkupplung (PDK) in various Porsche models. During this time Porsche has been able to extensively analyze and precisely evaluate the intervention and change behavior of the clutch system in many situations and under various conditions. This has resulted in an enhanced control strategy for the complex clutch system. By controlling the clutch change in a precise and highly dynamic way, it is possible to change gears much faster.

In addition, lightning shifts are implemented with a torque enhancement to improve driving performance. The dynamic torque enhancement uses the momentum and rotational energy that is present in the entire drive system during a gear change. In this process, the rotational energy (mass moment of inertia), which is stored primarily in the crankshaft, clutch module and gear wheel sets, is decelerated strongly while changing gear. This causes a brief additional torque boost in the drive system and allows a further improvement in the acceleration potential. The actual gear change occurs with high engine speed dynamics and a highly dynamic adaptation of the engine speed to the newly selected gear. The short synchronization times are in an order of magnitude that was previously reserved for motor sports.

Gear change

The new 911 GT3 has very short response and shifting times, which are clearly noticeable and help to enhance a sporty and emotive gear change. The engine fades out and in again at lightning speed during a full-throttle upshift for enhanced acoustic emotionality when changing gear. The lightning fade-out occurs when the gear change is initiated. Compared with its driving dynamics competitors, the new 911 GT3 allows gear changing without interruption in traction. The competitor vehicles with fast response times pay for acoustic emotionality with engine fade-out that interrupts traction and impacts negatively on vehicle acceleration.

With Porsche Doppelkupplung (PDK), fast gear changes without interruption in traction are achieved by precisely fine-tuning all gearshift and gear change functions. The specific characteristics of the PDK in the new 911 GT3 make it a particularly sporty model with driving dynamics-oriented and performance-oriented shift functions as well as emotional gear changes. Power transmission 3