Meeting the toughest of requirements – extreme "accelerated" testing
High speed in South Africa, high-temperature test in Arizona, cold shock in the Arctic Circle, chassis and suspension testing on the Nürburgring Nord-schleife (North Loop) – the development phases for the new Mercedes-Benz E 63 AMG were as diversified as they were unforgiving. Over a period of 19 months and a distance of 1.25 million test kilometres, the new-generation dynamic sports saloon offering everyday practicality was made ready for series production – and ambitious targets were achieved in terms of efficiency.
Before the first disguised test vehicles rolled through the factory gates at Affalterbach, the concept phase had to be completed. The purpose of the packaging tests which commenced in November 2005 was to test the entire car for functioning and feasibility.
Whether it was the suspension tuning, radiator and cooler efficiency, the airflow through the engine compartment or the durability of all the components – everything had to be analysed in advance by the AMG experts using a computer-based digital prototype (DPT). At the same time, the first engines and transmissions had to prove their performance capability and durability on various test rigs. Permanent stress in "accelerated" tests: full throttle from a standstill at a simulated 30 degrees C below zero, racetrack profiles with a high proportion of driving under full load and stop-and-go traffic in the city at 45 degrees C in the shade. Only once the precisely predefined development stages had been negotiated was the coveted go-ahead given.
At the same time, inconspicuous E 63 AMG models from the current W 211 series were on the road as component carriers or "mules". Equipped with numerous components from the successor model – such as the 6.3-litre V8 engine, SPEEDSHIFT MCT 7-speed sports transmission and RIDE CONTROL sports suspension – they help ensure effective testing of the new technologies before the new models (in-house code W 212) are even available. State-of-the-art measuring techniques provide the AMG engineers with invaluable data, with the focus on the temperatures of the coolant, transmission fluid and brake discs as well as the lap times on the handling course at the test track in Idiada, Spain and at the Nürburgring Nordschleife (North Loop), for example. Concept approval in autumn 2007 signals the start for the "real" prototypes
In this preliminary stage, the specialist departments define every aspect of the new E 63 AMG: bit by bit, they narrow down the choice of axle kinematics, radiator and cooler dimensions, springing and damping rates, and tyre compounds for further testing – not forgetting the crucial interaction between the different control units for the engine, transmission and dynamic handling control systems as well as their respective software versions. Following this concept approval, granted in autumn 2007, the first "real" AMG prototypes of the E 63 AMG were built – signalling the start of the extensive, standardised AMG development and testing programme.
This is when things get really serious for the 20 disguised test vehicles: tests in all of the world's climatic regions, from 85 metres below sea level in Death Valley in the US right up to Pikes Peak at an altitude of over 4400 metres. And from a bone-chilling minus 40 degrees in Swedish Lapland to plus 40 degrees in Arizona, USA. "We deliberately go to the extremes. It greatly helps us to save time and deal with the various aspects efficiently," says Tobias Moers, Head of Overall Vehicle Development at Mercedes-AMG.
AMG-specific test routes for loads that take it to the limit and beyond
It is simply not enough to consider the individual criteria such as heat, altitude and driving dynamics in isolation. It's rather a question of finding test routes that offer an opportunity to depict a combination of these three parameters. "We therefore take it to the limit and beyond, subjecting the car to far more load than any AMG customer ever will. And the new E 63 AMG has to overcome these tortures without a murmur of discontent," reports Oliver Wiech, Head of Overall E-Class Development.
High-speed test runs on a country road in South Africa, stretching for several miles and as straight as a die, are just as much part of the test procedure as driving at full throttle for many hours on the circular course in Nardo, southern Italy or at the proving ground in Arizona, USA. The E 63 AMG prototypes have to prove that the oil and water temperatures can stay in the green and that all of the seals and hose clamps are capable of withstanding the immense loads and stresses. The toughest test of all is saved for last: here the saloon has to race across the proving ground at top speed in temperatures of some 45 degrees plus before going straight into a garage where there is no draught and no wind – the engine's only relief being provided by the fan motor. Highly-sensitive electronic measuring systems with up to 500 measuring points per vehicle reveal even the most minor problems, which the AMG experts are able to pinpoint and put right immediately.
The high-temperature tests in Death Valley, USA are similarly extreme – albeit far less spectacular at first glance. Here, too, the summer temperatures approach the magical 50-degree mark, but slow cruising rather than hurtling at top speed is the order of the day here. Oliver Wiech: "We drive at an average of 35 km/h with maximum payload, climbing a steady ascent to the Daylight Pass – in the blazing sunshine and with a tarmac temperature of 80 degrees. The route is only 20 kilometres long, but there is no shade. Because the car is travelling so slowly, hardly any air flows through the radiator and engine compartment." No question about it: if a new high-tech performance car such as the E 63 AMG passes this test, it can also survive the daily stress of stop-and-go traffic in Shanghai or Dubai.
Vast know-how and wealth of precision engineering ensure low fuel consumption figures
But it is not all about extreme loads. Achieving the ambitious fuel-consumption targets also requires the developers' full concentration – as explained by Friedrich Eichler, who is in overall charge of engine and powertrain development: "To achieve an NEDC consumption figure of 12.6 litres per 100 kilometres, we put in a great deal of work in two areas: alternator management and transmission control." The system for recuperating braking energy when the vehicle is decelerating – being used at AMG for the first time – had to be tested and verified using every conceivable speed and drive profile. As did the new C (Controlled Efficiency) mode for the AMG SPEEDSHIFT MCT 7-speed sports transmission: "The deliberately early upshifts and low engine speeds play a key role in reducing fuel consumption," adds Eichler. Here it was a question of perfectly harmonising the AMG seven-speed sports transmission – equipped with a wet start-up clutch and four modes (C, S, S+ and M) – with the powerplant's response and vibration characteristics. A key part of this set-up involves ensuring that the dynamic power delivery of the AMG V8 engine developing 386 kW/525 hp and a torque of 630 Nm is provided at lightning speed when requested by the driver – a challenge which can only be overcome with vast know-how and a wealth of precision engineering, not to mention many simultaneous tests on public roads, test tracks and test rigs.
The brake tests on the Grossglockner Alpine pass road in Austria are a true test of endurance for the AMG high-performance braking system with internally ventilated discs all round and composite technology tested on the racetrack on the front axle. In contrast to the tests on the high-speed circuits, where the saloon is braked to a standstill from 250 km/h on countless occasions to test absolute performance, the focus here falls on a different aspect: fading. Loaded up to their permissible GVW, the E 63 AMG prototypes are sent from an altitude of just below 2600 metres through numerous hairpin bends down into the valley lying at 1151 metres. Meanwhile, the MCT sports transmission is simply idling, providing no engine braking whatsoever. As if this weren't enough, the test drivers also apply the brakes lightly between the switchbacks to generate additional heat – all of which places relentless thermal load on the brake discs, callipers, pads and fluid. What's more, the low speed prevents effective cooling of all the components. All the brake tests are carried out with the AMG high-performance braking system as well as with the new ceramic braking system.
Nordschleife proves the ultimate test for man and machine
The series of tests on the notorious Nürburgring Nordschleife (North Loop) – considered to be the world's toughest racing circuit – is equally extreme. Measuring 20.8 kilometres in length, the "big dipper" with its 73 bends stretches the E 63 AMG and its test drivers to the very limit. Every kilometre covered on the Nordschleife is equivalent to around seven kilometres on a normal road – the ultimate "accelerated" test for every new AMG model. This is where all the people who matter can be found: the suspension and tyre specialists, the handling dynamics experts, the transmission gurus and the team responsible for overall vehicle development. "If our 3-stage ESP® works here, it will work on any road in the world," laughs Tobias Moers, who gives his personal approval for every new AMG high-performance vehicle on the Nordschleife. Without exception.
Mercedes-AMG also runs its own test centre in the Eifel region to carry out its extensive development work: workshops, offices and test facilities devoted to customised development work occupy some 700 m2, all within earshot of the Nürburgring.
The tests in the wind tunnel are just as important as the test drives: here it is not just a question of simulating all routes and climatic conditions. The rapid change from hot to cold is of great assistance to the development engineers in their quest to take the vehicle and its components to the limit. Whether it be temperature, humidity, the angle of solar radiation or the airflow velocity – a state-of-the-art wind tunnel is an indispensable tool for every AMG vehicle.
Permanent exchange of information with AMG headquarters in Affalterbach
Testing, analysing, optimising – it all comes together at AMG headquarters, lo-cated at number 1 Daimlerstrasse in the Swabian town of Affalterbach. It is in this small town with a population of around 4600, situated to the north of Stuttgart in an idyllic location between fruit plantations and vineyards, that the development engineers meet up to discuss the topics raised and e-mailed in by colleagues around the globe. In this way, new parts and components can be sent from Affalterbach to Arjeplog by overnight express. And new software updates can be sent to Denver, USA via the internet.
"The precisely defined development processes at Mercedes-AMG ensure the hundred-percent quality standard. We owe our discerning customers this much. This is the only way the new E 63 AMG can achieve that which everyone has ultimately been working towards: overall vehicle approval," says Volker Mornhinweg, Chief Executive Officer of Mercedes-AMG GmbH.
The major test stages at a glance:
Development testing of the engine, transmission and powertrain
• Altitude tests in Denver, Colorado (USA), Lesotho (South Africa), Mont Ventoux (France) and Granada (Spain)
• High-temperature tests at Death Valley, California (USA), Upington (South Africa), Idiada proving ground (Spain) and Phoenix, Arizona (USA)
• Driving trials in Los Angeles, California (USA)
• Cold-temperature tests in Arctic Falls (Sweden)
• Climate-tunnel tests in Stuttgart
Development testing of the cooling and fuel systems
• Various driving trials on the high-speed tracks in Nardo (Italy) and Papen-burg
• Trials in Upington (South Africa) and Death Valley, California (USA)
• Wind-tunnel tests in Stuttgart
Development testing of the braking and control systems
• Brake testing on the high-speed track in Nardo (Italy) and the Grossglockner Alpine pass (Austria)
• Testing of dynamic handling control systems at the Idiada proving ground (Spain), in Arjeplog (Sweden) and at the Boxberg proving ground
In addition to these tests, individual components such as the engine, powertrain, transmission, axles and brakes, as well as the complete body structure, are tested to their limits on test rigs.
"Accelerated" endurance testing under the toughest of conditions
The extensive programme of vehicle development is supplemented by an endurance test which simulates an entire vehicle lifetime under the toughest of conditions in just a short time. The aim is to ensure the necessary degree of maturity before vehicle production can commence at the Mercedes-Benz plant in Sindelfingen.
The endurance testing at a glance:
Long-term testing on a variety of different roads:
• All the components and systems are tested together in everyday operation. Loaded up to their permitted gross vehicle weight, the test cars are put through a precisely defined test programme on country roads, on motorways and in city traffic.
"Heide" endurance testing:
• In this case, the developers focus on the durability of the chassis and suspension components, the entire bodyshell and the integral subframe on which the front axle, steering and engine are mounted. The test cars are loaded up to their permitted gross vehicle weight.
"Accelerated" endurance testing:
• Testing of the entire vehicle, focussing on the powertrain, chassis and suspension. Special features of the AMG programme include 10,000 kilometres on the Nürburgring Nordschleife (North Loop) and 10,000 kilometres in city traffic.
Full-load endurance testing:
• Extreme acceleration and braking manoeuvres with a high proportion of full-load operation, making extreme demands on the cooling, fuel-delivery and braking systems.
Corrosion endurance testing:
• Corrosion testing of the entire vehicle simulates the toughest dynamic and climatic environmental influences.
Final board approval:
• All-inclusive verification of the degree of development and production maturity.
These tests are supplemented by extensive crash simulations and real crash tests to provide the necessary evidence for country-specific certifications without which no registration would be possible.