smart roadster and roadster-coupé

COVER STORY Smart Roadster and Roadster-Coupé

2 ATZ worldwide 4/2003 Volume 105

With the Roadster and Roadster-Coupé, Smart has produced two compactopen-top vehicles providing sporty driving dynamics with a

mere 698 cm3 turbo engine. Their close technical kin-ship with the Smart City-Coupé demonstrates the

potential of this concept. The striking design ofboth models establishes a clear brand identi-

ty. Thanks to the innovative roof structureand numerous comfort and safety fea-tures, the new lightweight two-seatersrevive the traditions of the purist Roads-ters of the fifties and sixties.

1 Introduction

The two projects – the Smart Roadster andRoadster-Coupé, Figure 1 – were brought toproduction stage in a development periodof just 36 months. For both decidedly sportyvehicles, Smart managed to realise the con-cepts revealed in the form of two show cars– presented at the IAA 1999 in Frankfurtand the Paris Automobile Salon 2000 – withalmost no quality cutbacks. The SmartRoadster and Roadster-Coupé re-interpretthe tradition of the purist sporty two-seaterof the fifties and sixties, but with the addi-tion of the latest safety and comfort fea-tures. Powered by a 698 cm3 three-cylinderturbo engine with a 60 kW power output,the cars which weigh in at just 790 and 810

kg provide a maximum in driving pleasure.An even more economical 45-kW Roadstermodel is soon to be launched. The SmartRoadster and Roadster-Coupé also have aninnovative roof system, in which a hardtopand an electric folding top can be used to-gether or separately. The 60-kW Roadstercomes with a convertible top, while theRoadster-Cuopé is equipped with a hard-top. The short development phase was pos-sible thanks to the use of many compo-nents and modules from the Smart City-Coupé.

2 Design

2.1 Proportions and LayoutThe production project was triggered by the

By Hartmut Sinkwitz,

Heinz-Jürgen Neu,

Marc Hansmann,

Wolfgang Riedißer,

Hans-Hermann Bernd,

Martina Fischer,

Christoph Schulenburg

and Klaus Zinser

Smart Roadster und

Roadster-Coupé

You will find the figures mentioned in this article in the German issue of ATZ 4/2003 beginning on page 314.

Smart Roadster and Roadster-Coupé

3ATZ worldwide 4/2003 Volume 105

Roadster show car which appeared for thefirst time in 1999. In late 1998, a small teamof designers and engineers started work onthe development of an optimum conceptand harmonious proportions. The criteriawere clear to all involved: two seats, as lowa seat position as possible and with bodyoverhangs as small as possible. Whensketching the layout, the entire drive trainrear module of the City-Coupé was used,providing exceptionally good proportions.Super-streamlined and sporty at the front,short and firm at the back like a front-wheel drive. And in between a compact,low-slung passenger compartment.

2.2 ExteriorAt the same time as the proportion studies,the first sketch designs were produced:young, cheeky, full of character and typical-ly Smart. For the latter, the two-materialconcept with the Tridion safety cell andplastic body panels was carried over to theRoadster from the City-Coupé, and then fur-ther developed. The result is a visible struc-ture which fluidly connects the sills, sidepanels and roll bar, Figure 2.

The Roadster has also been given con-trast parts on the front and back which em-phasise the modular structure of the Smart.This provided new design possibilities forthe car's face: two headlights, one abovethe other, on each side of the vehicle stareout from the cylindrical recesses in the con-trast part which frames the headlight unitwith swinging contours. The bottom sec-tion of the front of the Roadster is dominat-ed by Smart's typically deep-set air intake –somewhat resembling a smiling face.

As well as the face, the athletic look ofthe Roadster was important to the design-ers. Thus, from a side view, the front fenderprojects clearly over the contour of thefront end. The rear fenders and the power-ful shoulders of the car body also go toprove that compact cars can also be shape-ly, Figure 3.

2.3 InteriorInside, a distictive feel of ambience was thetop priority. Its passengers should find itnot luxurious but pleasantly snug. This im-pression was consciously reinforced by thesymmetrically designed instrument panel.Two arcs divide the interior visually intotwo passenger compartments and extendthem forwards. Comfort is provided by twoSmart-typical upholstered cushions whichbreak up the volume of the instrumentpanel, Figure 4.

The motorbike-style instrument unitprojects from the left-hand upholsteredpad. Another fun touch is the pod-mountedrev. counter attached to the speedometer.

The unique Smart integral seats with back-rest nets underline the kinship of the Road-ster interior to that of the City-Coupé andConvertible.

It is particularly the materials and sur-faces in the interior which make the Road-ster a real Smart. Plastic contrast parts arecore-coloured in silver or metallic an-thracite. There are also plastic accent partswhich coordinate with the particular up-holstery colour. Both, together with trimsand textiles, create a pleasant ambience.The interior benefits particularly from thelove of detail and the Smart-specific mater-ial honesty.

2.4 From Show Car to ProductionIn summer 2000, there was no doubt: theRoadster presented as a show car was to befurther developed, as far as possible visual-ly unchanged, into a production vehicle.The objective was to overcome all the tech-nical obstacles arising so as to give the cus-tomer the opportunity to experience theradical nature of the show car as closely aspossible.

Only the bonnet length had to belenghtened, but this actually improved theRoadster's proportions. Dimensions andshape remained practically unchanged.

Inside, the design theme was retained inits entirety and was tailored to the techni-cal conditions. Some functional detailswere not yet present in the show car, for ex-ample controls and switches had to be inte-grated. The design theme of the doorcladding was taken and further developed.The same applies to an originally styled de-tail: the central armrest sits on the hand-brake lever even in the production Road-ster-Coupé.

3 Dimensional Concept

3.1 PrerequisitesExceptionally compact, fun to drive, com-fortable and suitable for everyday use:these attributes – typical of Smart – also de-termine the architecture of the Smart Road-ster and Roadster-Coupé. The car corre-sponds to a dimensional concept in whichmeasurements are kept small, the centre ofgravity is extremely low and the weight islight – all prerequisites for sporty drivingdynamics with a mere 698 cm3 turbo en-gine. This means that appealing drivingperformances can be obtained for a lowfuel consumption.

The low seat position allows for an over-all vehicle height of just 1192 mm taking ac-count of an acceptable headroom of 960mm (H61) and without reducing theground clearance to something like formu-la 1 levels, Figure 5.

3.2 Dimensions and CapacityWith a vehicle length of just 3427 mm and awidth of 1615 mm, in addition to the two 95percentile passengers, two luggage com-partments have also been included at thefront and back which, at 59 litres in the frontand 86 litres at the back (Roadster-Coupé:189 litres at the back), provide sufficient stor-age space for a weekend trip for two. In thefront compartment, a standard mineral wa-ter containes can even be accommodated.

The 35-litre fuel tank is located in thenon-deforming area between the enginecompartment and the passenger compart-ment and surrounded by the stable Tridionroll bar at the side.

Despite the compact size, even the dri-ver's footroom is of an exceptionally com-fortable design for this segment as noclutch pedal had to be accommodated dueto the automated gearbox concept.

Typical of Roadsters, the entrance area israther small. This is in part due to the gen-erously dimensioned body sills, which ben-efits both body rigidity and passenger safe-ty, and in part to the consciously ruggedroof side-members which emphasise thelow-slung character of the vehicle.

With the wheelbase of 2360 mm, and atrack of 1357 mm at the front and 1392 mmat the back, the prerequisites are in placefor truly nimble handling. Due to the mid-mounted engine concept, the weight distri-bution over the front and rear axles withthe driver on board is 44:56. To achieve thisvalue, amongst other things the batteryand the ESP hydro-unit are located respec-tively deep in and on the front axle cross-member.

A Roadster-typical power to weight-ra-tio was achieved by the low vehicle weight,despite all the latest safety and comfort fea-tures, by the rigorous light construction in-stead of high engine power. The compactvehicle dimensions also help keep thestructure lightweight.

3.3 Target WeightFurther measures to achieve the ambitioustarget weight of around 800 kg were:■ intensive CAD simulations and a numberof optimisation measures in the body shellusing high-tensile steel and modernprocesses such as the use of tailored blanks■ use of thermoplastic materials for non-structural outer skin panelling■ use of SMC material for the bonnet andboot■ side door structure as a mix of alumini-um extruded sections and aluminium shellparts in the hinge and lock area, glued dis-tortion-free■ cockpit bearing structure made of mag-nesium die-casting



■ luggage compartment at the front madeof reinforced plastic■ transfer of the compact, light drive linefrom the City-Coupé.

4 Roof System

The roof system comprises a hard top andan electrically operated folding coverwhich can be used together or separately.

4.1 Hard TopThe hard top is split lengthways along thecentre. Both roof shells are inserted with aguide pin each into the side-member mount-ing on the roll hoop. Three catches with levermechanisms fix them to the windscreenframe, with the middle one also joining thetwo shells firmly to each other. The side un-locking levers can only be opened by press-ing an integrated safety strip.

In a few simple steps, the roof segmentscan be removed and, packed in special plas-tic mouldings, stored one on top of the oth-er in the boot.

The 5-kg components are made of glass-fibre-reinforced polyurethane foam. Theirsurface forms a black foil on the outside(ASA/PC and PMMA), Figure 6. The inside ofthe hard top is padded with a pale grey tex-tile knit. The components are made by theinnovative long-fibre injection process(LFI): the foil and cover material are insert-ed in the tooling before the PU foam andglassfibre is injected.

4.2 Soft TopThe electrically operated folding roof, Fig-ure 7, can be opened to any position andclosed again at the press of a button. This ispossible whatever the speed of the vehicle,up to a maximum speed of 180 km/h.

The electronic system recognises theend positions by a rise in the power take-up. The vehicle management unit – SAM –then interrupts the power supply to theroof motor.

A powerfully designed electric motormoves the roof via two cables in a length-ways direction, driven by a gear wheel. Thisdrive pinion sits on the output shaft of thereducing gear.

The soft top drive unit is located central-ly on a steel cross-member under the insu-lation system of the boot.

Side guide rails made of U-shaped alu-minium extruded sections are bent to forman S and end at the front edge of the rollbar. This enables the roof to slide under theroll bar into the boot. The profiles run intothe removable roof side-members, whichconnect the A-pillar tips and roll hoop.

The structural elements of the foldingroof are one plastic cross-member at the

front and one at the rear end. These mem-bers are injected with black glassfibre-rein-forced polyamide (PA6GF30) and have astructured surface on their visible interior.The roof, of rubber-coated textile (poly-acrylic fabric on the outside, a core layer ofvulcanised rubber and polyester fabric onthe inside) is bonded to the front member,the roof top, and the rear one, the roof cap.Flat flexible plastic strips running parallelto the lateral edges of the roof ensure a de-fined fold of the fabric and so avoid kinks.

Special slides on the roof top, roof capand two central intermediate hoops are re-sponsible for guiding the folding roof bythe side rails.

The roof is locked and clamped in itsclosed state by closing mechanisms at theends of the roof top and roof cap, Figure 8.

Crosswise profiled seals with waterdrainage grooves prevent water getting in-side the Smart through the rear end face ofthe windscreen frame and the rear of theroof cap. At the roof corners, the drainagegrooves meet drainage channels whichroute any penetrating water to the outsidethrough A- and B- pillars. The lateral seal isformed by flat sealing channels: wire cablesin the flanks of the roof fabric enable theroof material to be securely tensioned.

4.2.1 Removable RoofSide-MembersBased on the convertible version of theSmart City-Coupé, both the Roadster andthe Roadster-Coupé have removable roofside-members (for the soft top). Its basicstructure is made of glassfibre-reinforcedpolyamide plastic. Its outer skin is made ofblack sheet steel. Two strong steel pins atthe rear ends form the link to the side-member mounting. Conically bevelledopenings help the pins insert. A movablebolt coupled to a locking mechanism is pro-vided for the A-pillar.

When the folding roof is fully opened,these side-members can be removed andstowed transverse in a mounting system inthe front luggage compartment.

An electric safety device prevents thefolding roof from being closed when theside-members are removed. Switches actu-ated by the lower rear guide pins of theside-members are responsible for this.

4.2.2 Operating SafetyOperating safety during loading is helpedby a folding, spring-loaded plastic strip onthe rear boot floor. When the soft top isopened, by its vertical position it preventsgoods in the boot coming into contact withthe fabric roof. When the roof is closed, thestrip is folded horizontally by the luggageon it, with a switch preventing the folding

roof from opening via a signal to the centralelectronics (SAM). This prevents incorrectoperation and thus damage to the roof sys-tem and luggage. With a system weight ofjust 14 kg, the roof module makes a percep-tible contribution to the low overall weightof the vehicle.

5 Acoustic Comfort

5.1 Sound DesignIn view of the sports car concept of theSmart Roadster and Roadster-Coupé, sounddesign played a central role in develop-ment. So, by emphasising the low-frequen-cy portion, the sound of the modest 698 cm3

three-cylinder engine is similar to that of asix-cylinder. On the one hand, attentionwas focussed on an exciting sporty noisesuitable for the vehicle type and contribut-ing to the vehicle's desirability and fascina-tion. To guarantee passengers relaxed andconcentrated driving even on long jour-neys, acoustic comfort requirements had tobe met over the entire rev. and speed range.

5.2 Insulation and VentilationOne of the classic conflicts occurs for exam-ple between optimising interior acousticsand interior ventilation. Here, the insula-tion system plays a key role. In the SmartRoadster and Roadster-Coupé, three highlyintegrated, light-weight components fulfilthe requirements. These are insulationcomponents, Figure 9, made from a sand-wich of polyurethane (PUR) foam, barrierfoil and dilutable needle fleece as the toplayer. The components are precisely gearedin terms of their surface structure on theshell side. Bonding to the steel plate surfaceis not necessary which crucially facilitatesassembly at this point. No damping foilsand heavy coating materials are thus need-ed.

Interior ventilation is via channels inte-grated in the interior lining. These liningshave likewise been optimised in terms ofinsulation and absorption. Placing the ven-tilation apertures close to the belt retractors(inside) and the rear lights (outside) en-sures that the function is compatible interms of acoustics, aerodynamics and de-sign.

6 Engine

For the new vehicles, two engine options of60 and 45 kW have been developed fromthe familiar three-cylinder turbo engine,Figure 10. Here, particular attention waspaid to a high torque with low rev. countsand responsive power for sporty driving. Itwas also important to meet EU 4 emissionrequirements.


5ATZ worldwide 4/2003 Volume 105

6.1 Power and TorqueThe cubic capacity of the three-cylinderwas increased from 599 to 698 cm3 bychanging the stroke and bore sizes. Thanksto a new turbo-charger version, it was pos-sible to increase the torque to 110 Nm forthe 60-kW version, Figure 11. The targetedlitre output of 85.7 kW/l in the 60-kW ver-sion has a strong position in the competi-tive environment, and likewise the effec-tive mean pressure which at 19.8 bar over arev. range of 2250 / min to 4500 / min isvery high. Fuel consumption stands at 5.1litres per 100 km.

6.2 Structural MeasuresBecause of the higher engine load, the nec-essary cooling performance in the cylinderhead was increased. It had to be ensured byincreasing the water chamber around thecombustion chambers, resulting in lowerpiston temperatures. Together with theomission of the compression surface andoptimised combustion chamber geometry,the knocking tendency fell while combus-tion improved.

A secondary air pump ensures the re-ox-idation of the exhaust, this being via a new-ly designed combination valve and intakeair duct through a steel pipe to the mani-fold flange which is fitted with an integrat-ed channel.

In both power versions, the Honeywell /Garrett turbo charger externally is thesame shape, but the compressor and tur-bine wheel and likewise the internal geom-etry have been adapted for the 60-kW ver-sion. This improved the flow dynamics. Thematerial used is a highly heatproof caststeel and the temperature of the incomingexhaust could thus be upped to a maxi-mum of 1050 °C. This improves efficiency.

6.3 Exhaust SystemFrom spring 2003, all new Smart vehicleswill comply with the statutory require-ments for EU 4. This has been achieved byreduced raw emissions and secondary airinjection in conjunction with the applica-tion of engine management. For the 60 kWRoadster and Roadster-Coupé, a larger cat-alytic converter volume has also been pro-vided. The system includes two monolithsof 900 cpsi and 600 cpsi.

7 Transmission

The Smart Roadster and Roadster-Coupéare fitted with the sequential automaticsix-speed gearbox known from the City-Coupé, which can be used manually or inautomatic mode. The transmission hasbeen adapted to the specific requirementsregarding gear transmission ratios, torque

and gear shift programme. It is operated ei-ther via the gear stick or paddles on thesteering wheel (optional extra).

8 Fuel SystemThe fuel system, Figure 12, is located be-tween the rear wall of the shell and the dri-ve unit. Excessive heat from the enginecompartment is checked by a bulkhead.The useful volume stands at 35 litres whichis displayed on the instrument cluster viaan eight bar system. As with a few othercomponents, the pump module, in a modi-fied form, was carried over from the City-Coupé. The active carbon canister, also acommon part, is regenerated over twostages: up to the partial load, the intakemanifold mainly generates the necessarynegative pressure; if there is charge pres-sure there, the venturi nozzle located infront of the turbo charger takes over thisfunction entirely.

9 Chassis

9.1 LayoutThe chassis is identical in the two versions:the Smart Roadster and Smart Roadster-Coupé. As in the familiar City-Coupé,McPherson struts are used on the front axleand a DeDion tube at the rear.

The Smart Roadster concept is based onthe City-Coupé chassis. To be able to posi-tion this diminutive Roadster in an attrac-tive price segment, the use of the commonparts is essential although characteristicvehicle data such as track and wheelbasehave been increased in line with the vehi-cle concept. Even Roadster-typical casterand camber changes could be producedwith the same wheel suspensions on thefront axles.

9.2 Design and BalancingThe production Roadster runs as standardon 185/55 R 15 tyres, with 205/50 R 15 (in theRoadster-Coupé: standard) or 205/45 R 16tyres available as an option.

Comparatively generous overall springtravels of 125 mm on the front axle and 122mm at the rear, allow a high level of springcomfort – measured against the standardfor this vehicle segment – yet retaining therequired agility. The low centre of gravityresults in very low dynamic axle load shifts,whereby the useful spring travels are onlyslightly restricted.

By adapting the spring and shock ab-sorber balancing, the choice of variable, di-rect steering gear ratio, together with theconcept of the rear powerplant with a mid-mounted engine and low centre of gravity,a sporty dynamic driving experience couldbe achieved, Figure 13. Thus, in comparison

with the Smart City-Coupé, despite usingmany of the same parts, a clear differencehas been obtained in terms of driving dy-namics and suspension comfort.

9.3 Driving DynamicsThe stationary cornering behavior is char-acterised by slight under-steering. The an-gles of drift occurring are small. Due to thelow seat position in the vehicle, the objec-tively measured roll angles appear subjec-tively substantially smaller. Despite themid-mounted engine and the rear wheeldrive, the Smart Roadster tends not to over-steer even at the limit.

Overall, the vehicle is characterised bythe desired sporty vivacious drive. As thepassenger and vehicle centres of gravityare very close, the vehicle reactions are feltvery directly, without distorting lever armsto the driver – one reason for the unusuallyspontaneous feedback experience.

Figure 14 compares the wheel steeringangle increase in relation to transverse ac-celeration of the Smart Roadster with thoseof the Smart City-Coupé. The comparative-ly lower values show the clearly lessmarked tendency of the Smart Roadster tounder-steer. Together with the more directsteering ratio, this results in a clearly lowersteering wheel-angle requirement, Figure15. Overall, the outcome is a more dynamicresponsiveness, even in the higher speedrange, which is clearly reflected particular-ly in the course of the function of angularrate of yaw reinforcement. Higher valueshere mean a stronger yaw reaction in rela-tion to the steering wheel angle introducedin each case. The Smart Roadster showstypical sports car values.

9.4 Driving Dynamics ControlSystemThe Roadster vehicles are fitted as standardwith the driving dynamics control systemESP (Electronic Stability Program): selectivebraking is used to stabilise the vehicle. ESPalso offers a few important additional fea-tures: starting and braking assistant, differ-ential lock and cornering brake control CBC,stabilisation under partial braking whencornering.

To provide every comfort for a hill start,as offered by automatic transmission witha torque converter, the Smart now has thestarting assistant AAS. When the brakepedal is released while the vehicle is sta-tionary, AAS keeps the wheels braked for afurther 0.7 seconds. There is thus enoughtime to move the foot from the brake pedalto the accelerator without the car rollingforwards or backwards due to the releasedclutch.

MATERIALSTitanium


9.5 SteeringWith the new steering, a modular systemwas created in which only three parts differmodel-specifically, namely housing, steer-ing rack and pinion. This enables the specif-ic requirements of City-Coupé and Roadsterto be met, as left or right hand drive, withmechanic or servo steering.

As seen previously in the City-Coupé,the running gear in the Roadster presents aparticular challenge in terms of packaging.It was important to define an arrangementof steering line and axle structural parts,which allow the front luggage compart-ment to be loaded with a mineral watercontainer.

In both the Roadster and Roadster-Coupé, electric power steering EPS is avail-able as an extra in the Comfort package.

In this way, Smart meets the customer'sdesire for good steering comfort, i.e. lowsteering forces especially when parking.Here, the maximum actuation forces on thesteering wheel fall by around two-thirds.The supporting force is controlled depend-ing on the vehicle speed and the force ex-erted on the steering wheel.

To ensure that steering returns to astraight direction, compensation for fric-tion is necessary in the system. The returnoccurs from the wheel due to the axle kine-matics. The servomotor works as a genera-tor on the basis of the passive excitationthus caused. Based on this signal, the con-trol unit detects a need for support and as-sists the returning force.

10 Electronics

10.1 StructureOne of the main development objectivesfor the Smart Roadster and Roadster-Coupéwas to ensure a broad palette of functional-ities and thus a very high customer benefitin this vehicle class by the use of intensive-ly networked electronics. To do so, compet-ing requirements had to be accommodated:a higher number of functions and specialfittings had to be housed in a very smallspace. For purposes of flexibility and inview of the different versions to be offered,the electronics structure comprises just afew control units each with a broad func-tional scope and integration level, Figure16.

10.2 Bus SystemThe CAN bus is the central data distributorin the Smart Roadster. It networks the con-trol units and thereby allows each one ac-cess to the information relevant to it. Thebus participants have been integrated forthe ESP (Electronic Stability Program) andEPS (Electric Power Steering) systems.

In addition, for the first time, Smart hasinstalled a LIN bus in the Roadster. It is ameans of cost-effectively connecting addi-tional simple control units and sensors.

10.3 Control Units10.3.1 Signal Capture and Trigger ModuleAs the central control unit, SAM (signal cap-ture and trigger module) takes on the rolesof power distribution and security. It alsocontrols the body functions. To this end, theSAM is connected to the CAN and LIN databuses. Relays and semi-conductor outputstages have been integrated in the SAM asthe switching elements. The control is car-ried out thus in detail:■ The locking system with remote controland drive lock: when the vehicle moves, theSAM locks the doors and protects againstunwanted intruders. In the event of a crash,the locked doors are automatically un-locked.■ The SAM also controls all the wipe func-tions in the Roadster. Linking via CAN al-lows, inter alia, the driving speed to beanalysed and the wiper control to be set ata drive speed-dependent rate. The rain sen-sor available as an optional extra is con-nected to the SAM via a LIN bus. With it,when windscreen wetting is detected, thewipe speed setting is fine tuned.■ In addition to the usual display of the di-rection of travel, practical touch-controlflashing has been integrated. A quick presson the steering column lever producesthree flashes.■ All light functions are controlled via SAMoutputs. In addition to the usual function-alities, this also allows the simple imple-mentation of special fittings such as thedaylight driving light and coming-home(switching on the vehicle lights by remotecontrol). With the twilight sensor integrat-ed in the rain sensor, automatic lightswitching (auto-light) is possible (optionalextra).■ The SAM also acts as a gateway to the LINbus, by transferring CAN data to the LINand vice versa. The rain sensor, on-boardcomputer and additional instruments areconnected to the LIN.

10.3.2 Instrument ClusterTo express the vehicle's sporty character, acompact, motorbike-like instrument clusterwas designed.

In addition to the usual display func-tions, a maintenance interval display hasalso been integrated in the instrumentcluster. It informs the customer of the timeor distance until the next workshop serviceby analysing driving style and other dri-ving conditions.

10.3.3 Engine, E-Gas and Transmission ControlIt is traditional for Smart to integrate all en-gine and drive functions in a single, highlysophisticated control unit (MEG). It takes onboth the classic engine management tasksand also the control of clutch and gears.This allows the efficient linking of engineand drive line functions so essential for in-novative features.

Like the City-Coupé, the Smart Roadsterhas an electronically controlled automaticmanual transmission (AMT). All the controlfunctions of the drive line, such as engag-ing and releasing the clutch and changinggear, are handled by actuators and con-trolled electronically. The Roadster driverdemands short interruptions in drag dur-ing gear-change and nimble driving – butalso easy gear changes. This is guaranteedby a complex software which controls thegear change operations.

In parallel, functions such as kickdownstarting – sporty starting with a high clutchengagement-speed and the acceleratorpedal fully depressed – and forced upshift –automatic upshift just before the speedlimiter cuts in – are covered.

Additional complexity arose due to theintegration of the driving dynamics controlsystem ESP, whose functions are imple-mented both in the braking system, by con-trolling the wheel brake cylinders, and inthe drive line, for example by slip control.

As a further optional extra, a tempomatwas also developed to control the drivingspeed, with a supplementary tempo limiterfunction to restrict it. In addition, the MEGprovides a range of monitoring functionsand diagnostics tests. System faults arethus detected immediately in all drivefunctions and signalled to the driver asthey arise. ■


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