Issue 1/2010

Porsche Engineering Magazine

Exclusive insights A smooth ride into the technological highlights of the with the Panamera’s air Boxster Spyder suspension

Something in the air at Intelligent light from Porsche Focus on aerodynamics helps to reduce accidents Contents

Editorial 3

About 4

Vehicle control systems 5 enable reproducible road tests

Intelligent light 8 helps to reduce accidents

Maximum efficiency 11 for noise-optimized gearing

In hot pursuit 14 with the Porsche Vehicle Tracking System

Something in the air at Porsche 16 Focus on aerodynamics

Hats off! 19 The Boxster Spyder

A smooth ride 23 with the Panamera’s

For fast-shifting drivers 26 Feel the shifting force

2 Porsche Engineering Magazine 1/2010 Editorial

Dear Readers,

Innovation and passion mean action and not just on our test track but in the minds of our employees as well. We are creative, and with our innovative ideas we help our customers to succeed.

In our projects, our engineers design a We always safeguard the confidentiality little piece of the future everyday. Accom- of our external customer projects. In or- pany us on a short journey through the der to give you an insight into our vehicle world of development and experience at development process, in this issue, we first hand our day-to-day fascination with present a Porsche highlight under the our work and our understanding of per- heading derivative development: the formance. new Boxster Spyder, which has set a new benchmark with its lightweight con- Take a look, for example, at the way we struction. The Panamera’s air suspen- develop vehicle control systems that sion system is our next step, not only is enable reproducible road tests and there - it light as a feather but more importantly fore not only yield reliable results but it ensures a smooth ride. above all save time and money in devel - opment. Safety is also an important is- Enjoy these and other highlights from sue when shaping the future. One bright the Porsche development department. spot in this issue is our intelligent light systems. Learn more about how Por- TIP: You can also read our magazine sche Engineering has contributed to a online at www.porsche-engineering.com/ reduction in traffic accidents as a result customermagazine. of these ingenious systems. From light- ing to our anti-theft system we show Enjoy this issue! you how and why Porsche customers need no longer fear having their vehi- Yours cles stolen. The Vehicle Tracking System Malte Radmann and Dirk Lappe from Porsche is the key to this peace of Managing Directors of mind. Porsche Engineering

Porsche Engineering Magazine 1/2010 3 Impressum

About Porsche Engineering News

At Porsche Engineering, engineers are tive developer for your project or would New Management at Porsche working on your behalf to come up with prefer a specialist systems developer, Engineering new and unusual ideas for vehicles and we can offer both, because Porsche industrial products. We develop a wide Engineering works at the interface be- On October 1, 2009, Malte Rad- variety of solutions for automotive man- tween these two areas. All the expertise mann was appointed chairman of ufacturers and suppliers, ranging from of Porsche Engineering converges in the executive board of Porsche En- designing individual components and Weissach, but it is available all over the gineering Group GmbH and Porsche complex modules to planning and im- world, including at your company’s of- Engineering Services GmbH. In both plementing complete vehicle develop- fices or production facilities. Wherever companies he succeeded Dr. Peter ment projects, including production we work, we bring a part of Porsche Schäfer, who moved at that time to start-up management. What makes our Engineering with us. To find out more Dr. Ing. h. c. F. Porsche AG, where he services special is that they are based about us, please request our image has taken the reins as Head of the on the expertise of a premium car man- brochure by email: Main Chassis Development Depart- ufacturer. Whether you need an automo- [email protected] ment.

Malte Radmann was previously a member of the executive board of both subsidiaries and the commer- cial director, a role in which he will continue.

The executive board will also wel- come Dirk Lappe, who has been re- sponsible for the Electrics/Electro- nics group at Porsche Engineering since 2002 and now holds the posi- tion of technical director.

Impressum • Porsche Engineering Magazine Porsche Engineering Magazine – now online too Publisher Editor Porsche Engineering Group GmbH Nicole Möller Our Porsche Engineering magazine Address Design: Machart–Design, Porsche Engineering Group GmbH Repro: Piltz Reproduktionen, Stuttgart is now available online: Porschestraße Printing: Leibfarth&Schwarz, Dettingen/Erms 71287 Weissach, Translation: Übersetzungen, www.porsche-engineering.com/ Stuttgart customermagazine Tel. +49 711 911-88888 Fax +49 711 911-88999 All rights reserved. No part of this publication may be reproduced without the prior permission of the E-mail: [email protected] publisher. We cannot guarantee that unrequested Website: www.porsche-engineering.com photos, slides, videos or manuscripts will be re- turned.

Porsche Engineering is a 100% subsidiary of Dr. Ing. h.c. F. Porsche AG

4 Porsche Engineering Magazine 1/2010 Electrics & Electronics Vehicle control systems

Vehicle control system to create reproducible road tests

Real road tests are an essential part of the development of modern vehicles. To date the challenge posed by test runs in the field has been the reproducibility of the trials. Porsche Engineering has made a great leap forward with this issue.

Components of the vehicle control system

DGPS module Control unit HMI module

Master Communications module

Communications module

Slave

DGPS module Control unit HMI module

When developing functions and testing context, Porsche Engineering has devel- is the control unit, to which the other various systems in the automotive sec- oped a special vehicle control system components such as the Differential tor, for example the driver assistance (VCS). The basic version of the vehicle Global Positioning System (DGPS) and systems, it is important to be able to control system comprises several com- the communication and Human Ma- reproduce a defined test scenario. In ponents in a modular structure. The chine Interface (HMI) modules are con- order to support the test driver in this central module and heart of this system nected.

Porsche Engineering Magazine 1/2010 5 Electrics & Electronics Vehicle control systems

The modular structure with defined in- accuracies, a differential GPS (DGPS) for example, transmits its actual data to terfaces offers numerous advantages. receiver is used. These receivers achieve the master, which then combines this For example, the modules can be ad- a greater accuracy in that they correct or information with its own actual data in justed either customer-specifically or better interpret the standard GPS signal. order to calculate the relative distance project-specifically. In addition, the ba- There are a multitude of different correc- between the two vehicles. sic system can be easily extended with tion and evaluation systems, which differ further components, such as the con- in terms of their accuracy, price, avail- Control unit nection to a vehicle bus. ability and in their properties. The control unit is the heart of the vehi- DGPS module A mobile DGPS receiver that is accurate cle control system, to which all other to within one meter and boasts high components are connected. Given the The vehicle control system works on availability was chosen for this vehicle multiple tasks and interfaces, the con- the basis of position location which control system. trol unit is also the most complex com- compares the current position with a ponent. Its main task is to serve as a reference position. In order to locate an Communications module central process controller. object’s position, services such as those of the Global Positioning System If several vehicles are involved in a test The tasks can be broken down into (GPS) can be used. However, given that case, wireless communication between the following: such services feature deviations in ex- the vehicles is required in the form of cess of ten meters, they are too inexact an ad hoc network. This is used to syn- I Test case recording by travelling for applications in a vehicle control chronize the progress of the test case. the route or manually marking land- system. The vehicle control system re- In addition, optional data such as GPS marks in a map quires an accuracy of less than 50 cen- coordinates can also be exchanged be- I Test case editing by changing timeters. In order to achieve these high tween the vehicles. The slave vehicle, the course or landmarks in a map I Reproduction of the test case by issuing instructions to the driver via the HMI I Evaluation of the test case

Human Machine Interface (HMI)

The vehicle control system makes it possible to reproduce saved test sce- narios under defined conditions and thereby run through them such that they can be compared. Particular atten- tion is placed here on the HMI being comprehensible, appropriate for the task and effective. With the assistance of the HMI, the test driver should be incorporated in the driving process through visual, haptic and acoustic Manual creation of a route feedback via the control device, as the

6 Porsche Engineering Magazine 1/2010 Electrics & Electronics Vehicle control systems

controller in a real road trial. Here the driver performs primarily stabilization Feedback strategies in the vehicle control system level driving tasks. As the longitudinal and transverse deviations must be kept Single mode Dual mode to a minimum while driving the target Stabilization level visual visual & haptic route – in order to guarantee the com- (Stage 1: Information) (Stage 2: Warning with parability requirement – real-time and call for action) E.g. Lane departure within unambiguous feedback to the driver is tolerance path E.g. Lane departure outside required. The table on the right pro- tolerance path vides an overview of the feedback strategies. Maneuver level visual visual & acoustic (Stage 1: Information for (Stage 2: Call for advance notice) action) An 8-inch display with touch function is used to provide visual feedback so that E.g. Symbols for E.g. Voice output to event display describe future events the test driver can start every drive independently via the interface. The dis- play enables the integration of a vehicle- independent vehicle control system with nal control. For the vehicle control sys- lane (or the stored “vehicle path” from minimal installation time. In order to tem we developed, the adherence to the GPS coordinates), a two-stage feed- guarantee contact with the road, a cam- prescribed speeds plays a decisive role. back strategy counteracts this. To en- era mounted on the windscreen displays The general requirement is that anti- hance the meaningfulness of the haptic a picture of the route ahead and the re- cipative dynamic driving handling (ac- feedback, it is combined with a visual quired feedback is crossfaded in. celeration/deceleration/cornering) be display which shows the direction of the displayed. As this is a simple control ac- correction to be made. The haptic module comprises two gloves tivity with little complexity, single mode with integrated vibration elements and a feedback is sufficient for this driving This control strategy with tolerance cor- control device which is connected to the task. A “follow-me” bar is placed across ridor and steering vibration on the hys- central control unit by USB. The vibration the road, showing the speed to be ad- teresis edge also corresponds to the gloves offer further feedback on the lat- hered to via a distance control. basic idea of the interaction metaphor eral guidance (see table above). presented here. The driver can move The vehicle lateral guidance in the vehi- freely within the objective limits and on- The distance and speed behavior of a cle control system is designed such ly when he reaches these will he receive vehicle are part of the vehicle longitudi- that when the vehicle leaves the driving tangible feedback.

Longitudinal and transverse correction No correction required required

Porsche Engineering Magazine 1/2010 7 Electrics & Electronics Intelligent Light

Intelligent light helps to reduce accidents

Road safety for all road users is the very top priority for Porsche Engineering. A new intelligent light system provides the required technical progress.

In the future, “marking light” will assist the driver while driving at night.

Current figures from the Federal Statis- tics in the years to come. On the other ly reduce the above figures. It is pre- tical Office in Germany (DESTATIS) hand, the absolute figures of 4,600 cisely while driving at twilight and in show that the number of road deaths dead and 407,000 injured road users darkness, when drivers find it most and road injuries in 2008 has fallen has long been sufficient reason for all re- difficult to identify objects in traffic, once again. While the continuing devel- sponsible institutions and communities that the probability of being involved opment of technical innovations in vehi- (incl. legislative, scientific and industrial) in an accident with other road users cles, such as for example improved to search for further improvements in a rises significantly. The cause of this in- side impact protection, has contributed bid to achieve accident-free driving. creased accident risk is the relatively significantly to this good news, it is not low level of ambient brightness togeth- the only factor. Increasingly, passive Worth a closer look er with the fact that drivers are sporad- safety systems have been supplement- ically dazzled by oncoming vehicles, ed by active ones in all vehicle classes Databases such as GIDAS (German In- which requires the human eye to adapt and this is set to further support the Depth Accident Study) show exactly quickly. Making things even more diffi- positive trend in vehicle accident statis- where potential still exists to effective- cult is the fact that the depth of field

8 Porsche Engineering Magazine 1/2010 Electrics & Electronics Intelligent Light

and the ability to see is reduced signifi- At the speed of light tion and classification of the named ob- cantly at night. jects in image sequences is highly com- The complex internal flow of informa- plex because the appearance or pose On the test stand tion between all participants involved of the objects to be detected can vary (peripherals and computing processes) hugely. For this reason, the process is Porsche Engineering is therefore coop- is mapped via a central real-time data- being subjected to particularly intense erating closely with the Karlsruhe Insti- base. This database not only synchro- scrutiny in the technical disciplines of tute of Technology (KIT) on research nizes all sensor and actuator conditions image processing and pattern recogni- into how vehicle drivers can be best per time unit, it also saves these for tion. Effective, developed image seg- assisted in their task when driving at more convenient evaluation, for exam- mentation and advance classification night. In this regard, various light-based ple at a workstation. on the basis of thermal image se- driver assistance systems are put through quences provides for a dual-adaptive their paces on the test stand. Particular Detection of pedestrians limit value filter. This algorithm brings attention is paid to a very promising and together two different limit values, which innovative light function, which is called The thermal imaging camera, which is are measured pixel by pixel on the basis “marking light”. In the near future, this used as a sensor system, also provides of the available image information. The system aims to avoid collisions with per- the driver with information on potential- following advance classification bina- sons (or indeed cyclists and animals) ly dangerous objects in his environment rizes the existing grayscale image utiliz- through targeted illumination, a light- through a technical analysis of the im- ing a highly sophisticated methodology. based marking system. age sequences. The detection and lo- Results of the dual-adaptive limit value calization of, for example, pedestrians, filter are shown here; these will be fur- In the spotlight cyclists and wildlife in front of the vehi- ther segmented in the next step of the cle plays a central role here. The detec- process. In order to keep the computing In order to be able to examine light- based assistance functions, a prototype structure was realized in which a hori- Numbers of persons killed in road traffic accidents 1953-2008 zontally and vertically swiveling Bi-

Xenon module and an LED-based “auto- ‘73: 0.8 per mil. — maximum limit in 1000 ‘72: Top speed motive spotlight” were integrated. Com- of 100 km/h 25 on secondary munication with the Bi-Xenon modules ‘74: Recommended speed on German motorways is based on the CAN (Controller Area roads Network) bus; the actuators and sen- 20 ‘80: Helmet requirement (fines) sors of the automotive spotlight are ‘84: Seatbelt requirement served by a real-time-capable prototyp- 15 ing unit. All thermal sensors have an ‘98: 0.5 per mil. — FIR (Far-Infrared, Ï = 8–12µm) cam- 10 maximum limit era, which offers a resolution of 320 x 240 pixel at a frame rate of 25 Hz. 5 4467 A multi-core processor system with sufficiently dimensioned resources is 0 available as the central computer for 1955 60 65 70 75 80 85 90 95 00 05 08* image processing and for downstream * provisional result © Federal Statistical Office of Germany, Wiesbaden 2009 strategic evaluations.

Porsche Engineering Magazine 1/2010 9 Electrics & Electronics Intelligent Light

time for the final classification to an ab- oriented gradients (HOG)”. Here the solute minimum, the previously men- shape and form of objects are de- tioned advance classification reduces scribed in an image segment using the the number of image sections using associated distribution and alignment heuristic assumptions. To this end the of locally calculated intensity gradi- object size, position within the image co- ents. In the approach selected, the ordinates, the width to height ratio and HOG descriptors are determined in the relationship with the bounding box three stages and then passed on to Determination of the intensity gradients of a are all evaluated in order to exclude as the final classifier: pedestrian as preparation for the classification many sources of incor rect classification as possible in advance. I Calculating the gradients via the Positive outlook intensity in the detection window, Preparation for classification I Determining the histogram via the The prospects for the described system orientation of the gradients, are positive, as initial simulation results One promising approach, as prepara- I Standardizing the histogram in have confirmed the expected high de- tion for the final classification, is based relation to a higher-level tection and classification rate in differ- on extracting features (symmetry, form- unit area. ent driving situations. In the next step, invariant characteristics etc) from im- test subject studies are planned in order age sections, which are assumed to Classification of pedestrians to obtain a representative statement as contain objects to be classified, e.g. whether and to what extent such innova- pedestrians, cyclists, wildlife. The classi- A “Support Vector Machine (SVM)” is tive light-based driver assistance sys- fication is performed here by means of used as the classifier; it learns how to tems can best support drivers in their an adaptive instance, which compares make classification decisions on the basis tasks. The resultant scientifically sound technical indicators of an image section of a number of training examples with findings will serve in the medium-term with previously learned knowledge. known classes. With this knowledge, it is to ensure that the active assistance in Those indicators for an efficient classifi- possible to classify objects successfully our vehicles is improved further and af- cation which have great potential are and efficiently in the following image ford our customers added value in terms those derived from the “histogram of sections from everyday driving situations. of their safety and comfort.

Active assistance in vehicles enhances safety and comfort.

10 Porsche Engineering Magazine 1/2010 Drivetrain Gearing

Heavenly efficiency: there shall be no grinding of teeth

As assemblies become increasingly complex, the requirements placed on gearing systems in and transmissions rise also. Moreover, as engines become quieter, the acoustic behavior of the gear wheels is pushed further into the spotlight.

However it is not just the complex This lays the foundations for acoustical- flanges endure peak that are requirements on the gearing and its ly optimizable gearing. ten times higher than a measuring side acous tics that are increasing constantly. shaft without an accompanying increase There is a simultaneous requirement to Turning the right wheel in the measurement error while pro - optimize the power-to-weight ratio of viding the same measurement accu - the components – two goals which are Customers of Porsche Engineering ben- racy. The complete encapsulation of the often in direct opposition. Therefore, efit from the new development method- measuring technology enables signifi- precise knowledge of the loads to be ology which enables efficient drivetrain cantly longer endurance test deploy- expected is gaining importance, while design while also giving due considera- ments compared to conventional sys- rising cost pressures are making the tion to customer specifications. tems. The patented flange application implementation of effective measures procedure makes it possible to run mis- more and more difficult. To define realistic load spectra, operat- use loads on the same test setup as the ing loads are recorded, not in expensive usual endurance tests, which signifi- Porsche Engineering is meeting this measuring hubs or on measuring side cantly reduces development costs. Only challenge head-on with an effective shafts, but rather on the flange of the with the assistance of these exact sig- strategy. First the gearing is designed transmission output shaft (see figure on nal qualities can a simulation environ- and optimized in terms of its load ca- page 12). The influence of the torsional ment to predict drivetrain loads be pacity using simulated load spectra, rigidity between the drive and output reliably verified in endurance tests. The based on measured data, which enable shafts can thereby be circumvented and heart of this calculation tool is a 3D a requirement-led design. There is a spe- creeping or permanent faults caused by route model for all standard Porsche cial focus on the load capacity which is plastic shaft deformations during meas- durability routes. For this, race, test and achieved without special modifications. urement are avoided. The measuring defined mixed routes with uphill and

Optimizing the drivetrain load by changing the operating strategy

Wheel/pinion load Changing the driving strategy

Function model Application data records Strategy 1 Strategy X

Integration of the control unit functions

Porsche Engineering Magazine 1/2010 11 Drivetrain Gearing

encompasses the real control unit func- Gear design Axle transmission tions as Software-in-the-Loop (SiL), so that the latest data statuses of the soft- After the new load spectra are defined, ware development can be tested for an iteration loop starts to determine their effect without the need to have pro- the optimal gear geometry, taking into totypes available. It is possible to make a consideration the requirements regard- statement, quickly and cost-effectively, ing service life and noise generation as to how the individual components of behavior (NVH). Thanks to their long the drivetrain are loaded by the current years of experience, Porsche Engi - Measuring flange software statuses and how an overload neering succeeded in resolving the of the current design can be counteract- conflict between load capacity and Measuring the operating/misuse loads ed by targeted interventions in the func- noise optimization. The final gear de- tions of the control unit. This procedure sign meets the service life expectation downhill sections were measured in de- thus enables the systematic examination and at the same time delivers a solid tail and stored in a database as a func- of the complex interactions between op- basis for subsequent optimization of tion of their latitude and longitude (see timal efficiency and drivetrain load within the gear noise, which can be influ en ced figure on the right). Using this method- the framework of variant calculations by making corrections to the tooth ology, the Porsche engineer is assured over several thousand kilometers. flanks. that the climbing resistance acting on the vehicle can be entered into the sim- ulation environment with a high level of 3D route model accuracy.

Realistic braking simulation using a synthetic driver model

To ensure that the load forecast can be made under realistic conditions, Porsche Engineering developed a new type of synthetic driver model with hu- man characteristics. This model is capa- ble of reproducing the accelerator and brake pedal positions almost exactly. Latitude The virtual driver works with a decision- Longitude making level and an action level, which process and implement the information in front of the vehicle. The combination of both levels prevents unrealistic accel- eration and delaying tactics, particularly Vehicle and driver model while driving in a curve.

The mechanical model of the vehicle, which is tailored to the application, also

12 Porsche Engineering Magazine 1/2010 Drivetrain Gearing

Representation of a tolerance cloud to evaluate stability and quality

σTE quality

NQDs in Tolerance (Extract)

Load Misalignment

stability

In addition, the noise behavior of the To optimize the noise generation be- moves on a scale from 0 to 10 and can gears is dependent on the to be havior, various corrections are made to be achieved through various combina- transferred (Md) and the environmental the tooth flanks and their influence on tions of quality and stability. influences acting on tooth engage- the noise generation determined. This ment. Shaft bending and inclination, leads to millions of variants, which are The practice of tolerance bearing clearances and housing rigidity evaluated in production in terms of their values all impact on tooth engagement acoustic suitability and the tolerance- The methodology presented produces and shift the contact pattern on the determined acoustic fluctuations. To a gearing system that is in line with ser - flanks depending on the load. These make this wealth of information more vice life requirements and optimized in influences can lead to gaps in the comprehensible, the noise excitation terms of the noise generated. In addi- tooth engagement and are factored diagram is reduced to just one value, tion, it is possible to create instructions in during optimization by altering mis- the Noise Quality Dimension (NQD) which for manufacturing as to which flank cor- alignment (ƒHβ). The “range of devia- describes the acoustic quality. rections have a particularly large impact tion of the transmission error” (σTE), on the acous tic stability of the gearing which derives from the tooth-rigidity- Next, the variance in the tolerance field system – and this can be done during determined transmission error, serves is determined; this is equivalent to the development before a single prototype as a measure of the tendency to gener- stability. The smaller the variance, the is ever built. Conversely, it is also possi- ate gearing noise. more stable the manufacturing process ble to determine the tolerances re- is. The art here lies in finding the ideal quired for a robust design and to open Noise generation compromise between quality and stabil- up individual tolerances in a targeted ity (see figure above). Both the quality fashion. This can lower manufacturing The 3-dimensional representation above and the stability parameters are en- costs without sacrificing acoustic quali- shows an ideal noise excitation dia- tered in a complex algorithm which cal- ty. The result is a design which is opti- gram with low reactions to changes in culates the final evaluation criterion: mized in terms of noise generation and load, ambient influences and small val- the “Noise Resistance to Tolerances” service life and which also factors in the ues for σTE. (NORTON). Like the ATZ ranking, this rising cost pressures within production.

Porsche Engineering Magazine 1/2010 13 Electrics & Electronics Vehicle Tracking System

The Porsche Vehicle Tracking System – Tracking Car Thieves

With the Porsche Vehicle Tracking System, the Porsche engineers have succeeded not only in enabling the remote location of a vehicle but also in utilizing further helpful ap- plications. Through networking with other control units, for example, it is possible to remotely trigger alarms on the vehicle or even the immobilizer.

The Porsche Vehicle Tracking System is used in many parts of Europe and can do much more than just locate vehicles.

14 Porsche Engineering Magazine 1/2010 Electrics & Electronics Vehicle Tracking System

The primary objective of the Vehicle vehicle. The server-supported location Tracking System development project “Porsche added certain fea- of the vehicle does not run constantly, was to satisfy the conditions set down by tures above and beyond the but only when it is actually needed, i.e. in insurance bodies in Europe. These de- serious cases. A silent alarm is triggered mand a location system for vehicles, for original development task. ” automatically when the vehicle is stolen example as of a certain value which varies or a manipulation has been detected or depending on the country. However, over following notification by the vehicle owner. the course of the development project, radius of 400 meters without the igni- Porsche added certain features to the Ve- tion being switched on (motion alarm). “Retrieval” hicle Tracking System above and beyond the original development task. This is And the engineers came up with much If the car is stolen or there is any surely why the system has become so more besides: depending on the coun- attemp ted manipulation, the Vehicle successful in the interim and has already try, the most varied differentiations of Tracking System in the vehicle sends an been implemented in 27 European coun- the Vehicle Tracking System have been alarm to the Security Operation Center tries as well as Russia and South Africa. created. For example, in certain coun- (SOC). The SOC contacts the customer tries, the police can activate the vehi- to verify the theft and automatically re- Well connected cle’s alarm system “remotely” through a ports the vehicle position to the police. central service center if requested. Also The Vehicle Tracking System was devel- the car can be prevented from starting As the SOC of the customer’s home oped, tested and released by Porsche using the engine lock function. country is always notified even if the engineers in Weissach – after more than theft takes place in another country, the one million test kilometers and in ex- Some underwriting associations also customer can always speak to SOC cess of 2,000 successfully completed require a “driver card” as additional cus- staff in his native language. By network- service tests. To this end, no detail, from tomer authentication. The customers’ ing the SOCs together, cases of theft packaging through networking and func - security request that the car can only can be processed using the “roaming” tion tests and up to closed-circuit cur- be released for driving after a key com- function. In this case, the SOC abroad rent measurements, was overlooked in bination is input via a remote control assumes responsibility for communica- ensuring that a fault-free system was was met with the development of the tions with local police. These then take brought to series production. “remote keypad”. If the key code is in- up the case and retrieve the vehicle. correct, too late or not input at all, a The engineers are particularly proud of corresponding message is sent to a In order to avoid dangerous situations, the integrated LIN authentication: for service center. which may occur for example while in example, the vehicle engine can only be pursuit of a vehicle, the SOC can pre- started once the Body Control Module Catch me if you can vent the vehicle from being started again. (BCM) has uniquely identified the corre- This means that once the thief switches sponding Vehicle Tracking System. This The Porsche Vehicle Tracking System off the vehicle, it cannot be restarted. makes it possible to protect the system works with the latest GPS technology. from a manipulation or bypass attempt. An integrated telephone module trans- The Vehicle Tracking System also makes If someone tries to steal or interfere mits all messages and commands be- it impossible to hide the vehicle in a with the vehicle, an alarm is triggered, tween the Vehicle Tracking System and crowd – for example in a large car park: for example, if the battery is discon- the Service Center. A GPS antenna, a the police can request that the hazard nected (sabotage alarm), the antenna is GSM antenna and the Vehicle Tracking warning lights and the alarm sirens be disconnected, the vehicle moves over a System control unit are installed in the activated remotely.

Porsche Engineering Magazine 1/2010 15 Special Aerodynamics

Something in the air at Porsche

Aerodynamic vehicles are hardly a new idea. Lower air resistance makes vehicles faster and more economical and Porsche has decades of experience to prove this.

The wind tunnel in Weissach is renowned for its excellent air flow quality.

16 Porsche Engineering Magazine 1/2010 Special Aerodynamics

Statutory regulations combined with the worldwide explosion in demand for “Even back then the air resistance of a Porsche was energy have increased the demand for almost half that of its competitor vehicles.” low-consumption, efficient vehicles with low CO2 emissions. The field of aerody- namics has a huge contribution to make towards lowering consumption. History’s no drag extraction of the air in the measuring section floor. At low speeds, for example in city driving, The constant battle for consumption the vehicle mass has a critical impact advantages and the key role that it plays Vehicles are not the only products for on fuel consumption. The air resis tance, in development are not new. The engi- which aerodynamics are key, however. which increases in line with the square neers at Porsche have been grappling Many exciting and challenging customer of the vehicle speed, already exceeds with solutions to counteract windforce projects have had to prove their aero- the rolling resistance as of approx. since as early as 1948. When develop- dynamic credentials here. 80 km/h (50 mph) and represents, par- ing the in Gmünd for ex- ticularly when driving cross-country and ample, the quality of the air-flow around From trains to cycle teams, umbrella on motorways, the lion’s share of the the vehicle was still being assessed as manufacturers to tent makers, Porsche entire external road resistance. the car drove past by documenting the Engineering has assisted on a vast range behavior of wool fibers attached to the of projects. Further below, we have de- As a result it is important to ensure that body. Even back then the air resistance tailed a small selection of our in-house the product of the drag coefficient and of a Porsche was almost half that of its aerodynamic stars. the frontal area (cd x A) is low. However, competitor vehicles. this is not the only task of vehicle aero- Going with the flow dynamics. Wool fibers are no longer used these days in Weissach. Instead, a broad range The demand for constant improvements To ensure the quality of an automobile, of simulation methods, including wind in performance and the required com- Porsche engineers are constantly working tunnels and computer-assisted calcula- pliance with increasingly stringent statu- on new solutions to improve features, tion methods, have been developed. tory conditions necessitates constant such as the straightahead tracking, lane - For example Porsche commissioned improvements in aerodynamics. History changing behavior, the crosswind sta- its own wind tunnel in the Research is only one of the reasons underlying bility and cooling of engines. and Development Centre in Weissach in our commitment to advancing the pio- 1986 and then started to make its neering development of aerodynamics The efficient cooling of gearboxes, brakes knowledge in the field of aerodynamics into the future. Our desire for excellence and individual components along with accessible to more than just its automo- is another. comfort issues such as wind noise, the tive customers. heating and ventilation of the interior or the soiling behavior, to men tion but The system is renowned to this day for a few of the many contributory factors, its excellent air-flow quality. It can also “For generations, we have depend on the air flow around and measure aerodynamic forces and mo- been working towards creat- even through the vehicle. For genera- ments at the same time as the pres- ing, quite literally, the least tions, we have been working towards sures acting on the vehicle. The bound- creating, quite literally, the least possi- ary layer thickness of the air flow can possible resistance.” ble resistance. be influenced as required by full-surface

Porsche Engineering Magazine 1/2010 17 Special Aerodynamics

Porsche has a long tradition of aerodynamic development

1948 1955 1971 1972

In order to assess the quality of the For the Avus high-speed track in As early as 1969, the The Carrera RS 2.7 was the first air flow around the vehicle, wool , the 550 Spyder was given a came in short tail and long tail 911 to boast a front and rear fibers were attached to the body cover for the side , the wheels forms. In 1971, the 917 long tail . The rear spoiler reduced of the 356. The 356/2 “Gmünd” and a small windshield. achieved a top speed of 386 km/h the large lift on the rear axle. achieved a drag coefficient of 0.29 on the Mulsanne Straight in Le A front spoiler was then also re- and had a frontal area of 1.62 m2. Mans. At the time, that was the quired to achieve the desired aero- This resulted in an astoundingly fastest speed a Porsche racing car dynamic balance between the front 2 good cd x A value of 0.470 m . had ever recorded during a race. and rear axles.

1986 1987 1988 1997

Thanks to the aerodynamically The S4 had a low The new 911 series 964 was launch- The 911 Carrera (996) with its cd = redesigned body with flat, lined front spoiler, a wide rear wing and ed in this year. Its particular develop- 0.30 demonstrated a significant underbody and effective wings, underbody paneling that covered ment feature was a radical aerody- improvement in the drag coefficient the 959 achieved a top speed of the entire front section of the body namic improvement of more than of the 911 series. The first-ever 317 km/h with a neutral aerody- as well as electrically controlled 10% compared to the predecessor water-cooled version of the 911 namic lift force on the rear axle. cooling air flaps. The cd value of model. The low cd value of 0.32 and had highly aerodynamic cooling air 0.34 was the best achieved by this the small frontal area of 1.79 m2 ducting with radiators arranged in 2 series. yielded a cd x A value of 0.573 m . front of the front wheels.

2000 2004 2006 2009

The Turbo (996) set a The cd values of the Porsche 911 The Porsche 911 Turbo (997) had One highlight of the Porsche new standard with a cd value of 0.3 l, Carrera (997) were, depending on a cd=0.31 and a negative lift coef- Panamera series is the active 4-way which made possible a speed of the version, between 0.28 and ficient of cl=-0.01. The wing ele- rear spoiler on the Porsche Panam- 305 km/h. This was also the first stan - 0.29. Despite larger frontal areas ment was made larger and thanks era Turbo, which thanks to optimal dard production car to feature an and higher cooling air requirements, to its aerodynamic design man- management of the attack angle and extendable wing element, which was the drag index of cd x A was at 0.56 ages on a smaller extension height. area geometry delivers maximum much more effective aerodynamically m2, less than the predecessor vehicle. New to the series: rear axle brake aerodynamics and performance. than the previous rear spoiler. The best in the Porsche 911 series. ventilation. S cd value: 0.29.

18 Porsche Engineering Magazine 1/2010 Complete Vehicle Boxster Spyder

Hats off! Boxster Spyder – The development of a Derivative

The projects that Porsche Engineering work on and for whom are often strictly classi- fied. That we develop Porsche derivatives however cannot be. Hats off to the new Boxster Spyder!

Uncompromising openness

The objective: extreme handling and velopment processes has yielded unri- package, it goes from 0 to 100 km/h high cornering acceleration – all these valled results. (62.5 mph) in 4.8 seconds. It has a top while keeping the vehicle light, strong, speed of 267 km/h (167 mph) – with its efficient and providing an open-air feel. When less is more top down. The vehicle rides 20 millime- The result is worthy of a second look! ters lower, which, together with the The various departments at Porsche At 1,275 kilograms, the Boxster Spyder weight reduction measures, means that Engineering have more than proven is the lightest model in the Porsche the center of gravity is lowered by 25 their overall vehicle competencies in range. Nevertheless, it produces 320 millimeters. The sporty chassis of the developing the Boxster Spyder, partic- hp – 10 hp more than the Boxster S. Boxster Spyder is characterized by its ularly in the area of modularisation. When equipped with the Porsche Dop- stiff and short springs, large anti-roll This coupled with the streamlined de- pelkupplung (PDK) and the Sport Chrono bars on the front and rear axles, and

Porsche Engineering Magazine 1/2010 19 Complete Vehicle Boxster Spyder

constructions and also to assess the Process steps in developing the top first detailed engineering design for the adjoining components. Based on the Defining the blank Acid test simulation results, the engineers and designers decided on the required de- I Securing loose top parts to the attach- I Check for accuracy of fit, functionality ments on the vehicle and look sign modifications. I Stipulation of seams and contours I Convertible top fulfills all technical an I Preparation of pattern in manual work visual requirements With this condensed design cycle, it I Coordination of all blank templates I Check of top contour using contour with respect to seam segments and lines templates was possible to release the design quickly followed by the tooling design release just one month later. The first component tests and module trials Labeling and digitizing the completed blank templates commenced just twelve months after

I Pattern for the cutter the start of the project. I Determining the optimal material utilization and consumption The development of the convertible top starts with the definition of the blank. During the first Open to all trim loop, loose material parts of the top are attached to the fixtures on the vehicle by means of adhesive tape and clips, in order to then determine seams and contours. The material parts are removed one after the other and manually transferred onto patterns. Next the blank templates In terms of the “headgear” one thing are coordinated with one another in terms of the seam segments and seam lines and became clear very quickly: an open ve- supplemented with seam allowances, notches and markings. hicle concept – as the name implies – requires that there be no roof at all. Least of all an electric one. If push specially tuned tension and pressure a wealth of inventiveness, particularly in comes to shove, perhaps a manual stages of its four shock absorbers. terms of the paintwork processes and one. For this sporty vehicle, an ‘emer- final vehicle assembly. Adopting simul- gency top’ for purists was developed. A lid for the rear taneous engineering philosophy, finite This two-part structure makes it possi- element models for casting, static and ble to use the top purely as a sun- The rear lid, an important identifying dynamic strength simulations were per- shield, creating a completely new driv- feature of the vehicle, posed a particu- formed as early as the styling phase ing experience. Porsche Engineering lar challenge for the Porsche Engineer- using the initial CAD surfaces. These developed, tested and released this ing development team. Its large size, simu lation tools were used to assess emergency top through to series pro- measuring 1.5 square meters, required the potential use of different lightweight duction. Complete Vehicle Boxster Spyder

Rear with Carrera GT-look scoops

Liberated mented during development of the con- fore at the very top of the performance vertible top covering. Unnecessary and specification for the Porsche Engineer- All the development goals were achieved. expensive extras, such as roof liners, ing´s chassis developer. To achieve this The result is a very light and easy to use were omitted and the number of com- goal, however, driving comfort, a feature soft top that offers the driver protection ponents minimized. Once the design that is very important for the driver was from the wind and rain. There is no was completed, the next step was to indeed not ignored. Extensive fine-tun- missing out on any fun with the hood on handover the project to the production ing on the suspension and damping either; it is possible to reach a top suppliers. They were supplied the elec- yielded a very successful compromise speed of 200 km/h (125 mph) with the tronic template set, a master sample, between driving comfort and driving dy- emergency top fitted. the parts list and detailed sewing and namics. Compared to the basic model, assembly instructions. With this infor- the developer was right on track with a The most striking technical feature of mation, the suppliers were able to start number of key chassis changes that the top is the unique design style, that the industrialization process which in- were made to the Boxster Spyder. The makes it possible to fold the top opti- cludes procuring the various parts and central feature is a sports chassis that mally and stow it in the luggage com- partment without reducing the luggage compartment space. In fact, the manual Comparison of wheel assembly weights of the Boxster Spyder and Boxster S top is very easy to use because there are just a few connection points on the 19-inch Boxster Spyder wheel 19-inch Boxster Spyder wheel to 19- vehicle and it can be fitted and stowed to 18-inch Boxster S wheel inch Boxster S Carrera sports wheel very quickly. The top is fixed across the Front axle -3% -9% roof frame to the cowl frame by means Rear axle -2% -12% of a tension cable behind the roll-over bar and over the fins on the rear lid. The soft top contour is additionally shaped equipment required for series produc- has been lowered by 20 millimeters and by a bow on the roll-over bar which pro- tion, creating the patterns, drafting and features conventional damping. Added duces an elegant line. The type of mate- fitting instructions and setting up the to this was a mechanical rear differential rials, e.g. carbon fiber and aluminum, production line. The aim is to always lock installed as standard which is of- were also chosen for their lightweight achieve optimal coordination between fered only as an option for the basic properties. developers and suppliers. Boxster model. As part of the light- weight construction, 8.5J x 19” and The essentials at a glance The Boxster Spyder is a very sporty vari- 10J x 19” unique and weight-optimized ant of the Boxster series. Further en- wheels were developed. Summer tires The requirements placed on the top hancements in driving pleasure, driving with dimensions of 235/40 R19 and were consistently pursued and imple- dynamics and performance were there- 265/35 R19 are fitted as standard.

Porsche Engineering Magazine 1/2010 21 Complete Vehicle Boxster Spyder

Light, efficient and open

Easy going axle. This reduces the pitching sensitivity neous steering behavior. These require- when driving over bumps and enables a ments were achieved by balancing the The wheels are cast aluminum wheels higher lateral acceleration. ratio of rebound and compression dam- manufactured using the flow-forming ping. The stabilizers were specifically de- method. Porsche Engineering was res - The core of the driving dynamic design signed to generate high rolling-resistant ponsible for the complete development is the design of the shock absorber. and neutral rolling rate distribution. This of all components. Furthermore, the Special attention was paid to ensure a chassis tuning resulted in very agile, pre- supplier’s finite element calculations highly dynamic roll stability, minimal dy- cise handling and neutral setup that were counterchecked and assessed, namic change of wheel load for optimal achieved maximum lateral acceleration their development process coordinated traction on the driven axle and a fast coupled with the driving comfort that is and monitored, as were all external and response from both axles for sponta- expected from vehicles of this class. internal tests used for sampling and re- lease. The result of this optimization is a reduction in wheel weight and therefore a reduction in unsprung mass.

The driving dynamics-oriented design of the Boxster Spyder benefits from the al- ready excellent dynamic driving charac- teristics of the Boxster model. Lowering the vehicle trim provided further poten- tial through a lower center of gravity. The main springs were redesigned to cater for the chassis being lowered by 20 mil- limeters, the change in vehicle mass and the driving-dynamic requirements. In the design position, the stiffness levels re- sulted in an increased structural reso- nant frequency from the front to the rear The aluminum cast wheels are manufactured using flow-forming technology.

22 Porsche Engineering Magazine 1/2010 Drivetrain Air suspension

A smooth ride – the Porsche Panamera air suspension

With the active air-sprung chassis on the new Porsche Panamera, the Porsche engineers have succeeded in creating the best possible balance between driving dynamics and comfort.

Components and parts of the air suspension

For the first time, the new Porsche and excellent control. Driving pleasure height sensors, a pressure sensor, a Panamera offers the driver the opportu- and the agility of the vehicle were like- temperature sensor, three body acceler- nity to select whether he wants to drive wise right at the top of the require- ation sensors as well as a control unit a comfortable, sporty car or a distinctly ments list. for the air suspension and Porsche Ac- dynamically-tuned one. The engineers tive Suspension Management System succeeded in producing a car that is as Harmony of components (PASM). comfortable as it is sporty, with power far beyond that previously known, The new air suspension which was built Better closed than open through the introduction of one single from scratch with a lightweight design system. To create the driving character- comprises four air springs with addi- The air supply system is a pioneering istics that are synonymous with Porsche, tional air volume valve on demand to innovation, which provides compressed important guidelines were created for change the spring rate. It also features air to the air suspension. It is character- the chassis and suspension systems of an air supply system with , ized by its closed operating principle. In the new Porsche Panamera: maximum accumulator and solenoid valve block. closed systems, the energy level in the driving dynamics, outstanding traction Rounding off the components are four vehicle is maintained, which has certain

Porsche Engineering Magazine 1/2010 23 Drivetrain Air suspension

attendant advantages. In an open sys- Compressor for the tem, air from the environment is filled closed air suspension into an accumulator. It is from this that the air springs are filled when the vehi- cle is raised or loaded. When reducing the load or lowering the vehicle, air is released out into the environment. In a closed system, the air quantity required for the control operations is taken from an accumulator into the air springs and then returned.

The very low pressure differences pre- vailing in the closed system enhance its efficiency significantly. Moreover the closed system reduces energy consump- State-of-the-art control lection but also by the driving and vehi- tion by around one third and reduces the cle conditions at that time. In addition compressor runtime by about a quarter, The switchable spring rates primarily in- to the horizontal-dynamic processes, while still providing superior control volve a newly developed valve which is the vertical-dynamic movements are al- speed, which is not the case with open integrated in the air springs and a con- so factored into the calculations in or- function systems. trol strategy which was developed and der to determine the ideal switching coordinated specifically for the require- time, the optimum of which is always The closed air supply and the compres- ments of the Porsche Panamera. the current required level. In addition, sor developed especially for its applica- body- and wheel-dominant signal shares tion in the Panamera represents the The Porsche engineers developed a must be detected, which can result in first time it has ever been used by a pre- complex control strategy to switch the spring rate adjustments depending on mium European automotive manufac- spring rates, as the switching process is the behavior of different strategies. Fur- turer in a luxury class car. influenced not only by the driver’s se- thermore, numerous special situations, for example the air volume heating up while driving, must be taken into consid- eration by the switching strategy. The Air-spring strut on the front axle aim of this control is that the vehicle al- ways displays the same familiar and Top mount Additional air volume valve foreseeable driving behavior for the Bump stop Additional air volume (on demand) driver, even in Sport Plus mode. Basic air volume Air spring boot (spring) A heavy lightweight External guide Protection bellows PASM shock With the air springs, the engineers at absorber Porsche succeeded in combining the high kingpin inclination of the spring rates with a compact design. A major factor here was the development of an

24 Porsche Engineering Magazine 1/2010 Drivetrain Air suspension

Front axle of the Porsche Panamera Turbo Rear axle of the Porsche Panamera Turbo

additional volume valve, which is both arranged on the air damper) with inte - Total control smaller and lighter than the current grated additional volume and switching state of the art. The lightweight design valve. Another feature of the rear axle Faced with the large system scope is supported by the arrangement of the air spring is that this is the first time and the multitude of power outputs in air springs, which minimizes the re- that a free-standing air spring with ex- the Porsche Panamera air suspension, quired air volume. ternal guide has been used to enhance Porsche developed a new hardware plat- comfort. Through the consistent use of form for the control unit. The same con- In addition to the large kingpin inclina- plastics, the weight of the air spring trol unit is also used as a variant for the tion and the low component weight, it module was reduced significantly. PASM system without air suspension. was of huge importance for the air springs that a very comfortable suspen- No detail is too small Strategic control sion behavior be achieved. This is criti- cal for the perception of comfort in this The engineers at Porsche in coopera- The individual software modules are vehicle class. This challenge was met in tion with the development and system structured modularly and designed such that very thin-walled air spring boots suppliers also developed a compressor that they can be used again in subse- with appropriately selected rubber mix- specifically for use in a closed air sus- quent projects. Before creating an ECU es were used in combination with a pension. , compressor, software program, the software develop- thin-walled aluminum external guide. dryer and switch valves have all been in- er can at an early stage use a PC to simu- The front axle is a double-wishbone tegrated into one module. This offers a late the functionality of his module or axle, on which the air springs including weight advantage of around one kilo- component, with the help of MIL (Model- switching valve and additional volume gram when compared to open air sus- in-the-Loop) or SIL (Software-in-the-Loop), form a compact unit together with the pensions. The air supply system is water- or, using appropriate hardware (for exam- damper. In the multi-link rear axle, the tight and completely maintenance-free. ple an autobox), can test them directly on damper and the air spring unit are arran - To supplement for leaks and to com- the vehicle without being dependent on ged separately. pensate for high temperature fluctua- the creation of a complete ECU software tions, air is topped up from the environ- package. This led to a significantly re- Despite very limited space, it proved ment. To avert freezing, a complex reg- duced development time and guaranteed possible to develop a free-standing air ulation strategy was developed which huge flexibility in the development pro - spring (air spring that is not coaxially makes it possible to dry the air. cess and during software updates.

Porsche Engineering Magazine 1/2010 25 Drivetrain Shifting force simulator

Feel the shifting force

To ensure optimal shifting comfort and a shift response that is typical of the brand — these are the requirements that Porsche Engineering have always and ever held dear.

The second generation shifting force simulator developed by Porsche Engineering now offers a broader application spectrum

Since 2005 Porsche Engineering has only used in isolated cases. Since the person thus takes up his actual position used the first generation of its own, in- completion of the first shifting force sim- as if being in the vehicle. The realistic ternally developed simulator both for ulator at Porsche, it has been possible to seat position means that the simulator its in-house and customer developments. marry the experience gained in testing also takes ergo nomic influences on the The simulator makes the shifting force with the variable options offered by sim- shifting process into consideration. of any gear tangible right from the very ulation. Even before the availability of the early concept phase, making it possible first real prototypes, the shifting charac - Real-time simulation software maps to save on valuable development time teristics can be perceived, evaluated the gear shifting. In addition to shifting- and costs. subjectively and initial optimizations can specific parameters, the influences of be defined. the vehicle on the transmission are also Up until a few years ago, the definition of taken into consideration here, for exam- new vehicle shifting patterns in the early The simulator is combined with a one ple through the transmission mounting development stages relied almost exclu- to one scaled driver seat, with which or the side shafts. The shifting forces sively on the experience of a handful of the relevant driver environment can be are calculated in real-time and made engineers, while pure simulations were reproduced vehicle-specifically. The test tangible on the gearshift lever by means

26 Porsche Engineering Magazine 1/2010 Drivetrain Shifting force simulator

of special electric motors. The impact of the smallest changes to the computer- assisted parameters is immediately perceptible on the gearshift lever. If what is felt is not what is desired, the shifting forces, paths and geometries can be redefined and optimized in real time at the click of a mouse.

The system developed by Porsche Engi- neering assists automotive engineers already in the concept phase to define the desired power transmission charac- teristics. Thus the shifting comfort can be evaluated objectively and repro- ducibly at an early stage in the project. Furthermore, it is possible in every de- Second generation actuators velopment phase and under the same framework conditions to check whether However, it was not only the computing of shifting impulses, malfunctions can the desired shifting characteristics can power of the real-time unit that was im- also be represented with greater accu- still be maintained without having to proved. While the actuators of the first racy, regardless of whether they involve use a prototype transmission. generation were designed for comfort doubled pressure points or gear clash shifting, the second generation of the at low temperatures or are due to vibra- Based on the the experience gained from simulator is also capable of generating tions in the drivetrain. In addition to the a multitude of customer development pro - forces that would only occur with very shifting direction, combined investiga- jects and in-house Porsche applications, sporty shifting. tions with the selection direction are this year sees the completion of the sec- also possible, for example a study of ond generation of the Porsche shifting To this end, special rotatory electric the influence of various gear selection force simulator, which has been complet- motors were used, which were exclu- characteristics and gate contours on ed an dalready been sucessfully used in sively developed for Porsche Engineer- the transverse shifting ability. Safety- development. Thanks to the ing. In the shifting direction, two of lock forces can also be felt and adjust- significantly greater computing power of these motors are run in parallel in order ed at the touch of a button. the new simulator, combined with a newly to be able to supply maximum forces developed procedure to optimize comput- while maintaining a consistently high The shifting force simulator offers an ing time, it is now possible to run the same level of dynamism. In the selection di - advantage in that it is not just finished models in the classic shifting simulation rection, one motor outputs the calculated components that are “brought to life”. (offline/ PC) and on the shifting force sim- forces. In the simulation process it is possible ulator (real-time hardware). Conse quently, to evaluate ideas and designs, for which high-precision blocking synchronizer mod- All in all, the completely new second only preliminary specification is available els can be used, which were previously generation of the shifting force simu- at the time. With the simulation system, only possible in the offline simulation. lator offers a significantly expanded it is possible to quickly identify promis- The effort involved in creating real-time range of applications. In addition to the ing designs and then focus on the detail models is also significantly reduced by adjustment of the engagement force in design engineering and on the imple- the act of standardizing the models. the shifting direction and the evaluation mentation of the technology.

Porsche Engineering Magazine 1/2010 27 Please visit www.porsche-consulting.com for further information.

There are many ways of optimizing developments. But more than two would be wasteful.

Development services: Porsche Engineering. Development process: Porsche Consulting.