Maybach - The World Premiere | Part Four

Aero-acoustics: the minimisation of noise

As in the areas of lightweight construction, safety and aerodynamics, the engineers developing the bodyshell of the Maybach were also at pains to achieve a level of noise comfort which would do justice to this high-end luxury car. Most of this effort was devoted to the avoidance of wind noise, the reduction of tyre and road noise and sound insulation measures for the interior - and with excellent results.

In order to trace acoustic disturbances at source the specialists spent hundreds of hours in the aero-acoustics tunnel, using special microphones and sensors to identify body features which caused wind noise or vibration. The vanes in the front bumper, the exterior mirrors, the A-pillars and the window and roof surfaces were aero-acoustically optimised by this means. The sophisticated sealing systems in the joints of detachable body components, which effectively reduce wind noise in the gaps even at high speeds, are also a result of painstaking, detailed work in the wind tunnel.

Extensive noise insulation measures on various body components help to prevent any remaining wind noise from penetrating into the interior. These include continuous sealing strips on the doors and additional seals on the front wings and roof pillars.

The Maybach engineers paid particular attention to low-frequency noises resulting from vibration in large-area components. It was aero-acoustic measurements that provided important information for the rigid, low-vibration design of the underfloor panelling and its attachment points, for example. The specialists prevented the thrumming that could affect ride comfort when the sliding sunroof is open by fitting an air deflector with four precisely calculated notches in its profile. These create small areas of turbulence and so avoid irritating noises.

Glass technology: noise insulation with plastic membranes

Sophisticated glass technology also plays a major part in the high level of noise comfort in the Maybach: the side windows are of newly developed, laminated glass containing an intermediate layer of four plastic membranes. One of these membranes (0.76 millimetres) is an acoustic insulator and significantly reduces noise in the interior.

The side windows of the Maybach have an overall thickness of 7.2 millimetres - 2.2 millimetres more than conventional laminated glass. Improved break-in security is a useful side-effect of this sophisticated glass technology, as the laminated glass makes the side windows considerably more difficult to break. The windscreen and rear window likewise incorporate acoustically effective plastic membranes and have a glass thickness of
6.2 millimetres.

Last but not least, the grey-tinted glass in the Maybach makes a major contribution to climatic comfort. It not only filters out UV radiation but also reflects the infra-red light in the sun's spectrum, which accounts for about 53 per cent of the entire energy transmitted by sunlight and plays a major part in heating up the interior. Depending on wavelength, a coating of pure silver and other high-quality metallic oxides reduces infra-red radiation into the interior with an efficiency of up to 80 per cent. Compared to glass with a conventional green tint, the overall transmission of energy into the interior through the windscreen is reduced from 60 to approx. 47 per cent and through the side windows from 44 to 36 per cent, thanks to infra-red reflection.

Panoramic roof: transparency at the touch of a button

The innovative, electro-transparent panoramic roof of the Maybach 62 is a highlight of a very special kind. With its elegant cassette structure of exotic wood it extends across the rear section like a glass dome and offers the rear passengers a unique ability to select an individual lighting atmosphere. The manufacturing process for this high-tech glass system is also absolutely typical of the Maybach: it is hand-crafted.

The optional panoramic roof is divided into two halves: the front section incorporates 30 solar cells over an area of approx. 0.5 square metres which convert sunlight into electrical energy and power the ventilation fan of the front climate control system in the Maybach 62 with an output of up to 63 Watts. This solar power flows as soon as the car is parked, and ensures a continuous circulation of fresh air in the interior.

The rear section of the panoramic roof features a number of technical innovations over an area of approx. 0.75 square metres. This roof section consists of two approx. six-millimetre thick panes of glass with an electrically powered, sliding liner between them. The laminated glass pane on the inside has an intermediate layer in the form of a liquid crystal membrane of conductive polymer plastic. The membrane has a cable connection to a control unit which generates an AC output of 90 volts. Switching the power on arranges the crystals in the plastic membrane in such a way that the glass becomes transparent and allows daylight into the rear of the Maybach 62 over its entire area. The special feature is that as soon as the AC voltage is switched off, the liquid crystals lose their transparent arrangement and the light is fragmented in all directions. The glass becomes opaque and filters the daylight to produce a pleasant, diffused glow, with only approx. 76 per cent reaching the interior. This electrically controlled transparency has its world premiere in the Maybach 62.

Thanks to this unique roof technology the rear passengers in this luxury motor car can decide in accordance with their mood or the weather conditions whether to enjoy a bright interior flooded with daylight in which to admire an exclusive, panoramic view of the scenery, or whether to relax beneath a semi-transparent glass dome. For dull weather conditions or longer journeys by night the panoramic roof has yet another highlight for an individual interior lighting effect: an illuminated sliding liner.

Apart from the electro-transparent panoramic roof Maybach customers have numerous other possibilities where roof design is concerned. In the Maybach 62 they are able to choose between an aluminium roof with an integrated solar module or an electrically operated sliding/tilting sunroof for the rear section with or without a solar module. In both cases an electrically operated, sliding liner is included.

Headlamps: lighting features for an unmistakable identity

Taking a close look at the headlamps of the luxury limousine reveals a good example of the attention to detail lavished on the Maybach by its developers: the lenses of the bi-xenon headlamps bear the double-M emblem of the Maybach craft shop - a subtle reinforcement of product identity which is at the same time reminiscent of the legendary Maybach "Zeppelin" of 1930, whose headlamp lenses bore the company trademark.

Bi-xenon is a synonym for the best and most efficient headlamp technology. The great advantages of this system include outstanding brilliance, long range and particularly uniform illumination of the road surface, an important contribution to active safety. The powerful gas discharge headlamps generate their low and main beam with a xenon bulb: while the entire light output is available at main beam, a shutter slides between the lamp and the lens to obscure part of the beam when switching to low beam. When main beam is selected the halogen spotlights (H7) in the inner headlamps are also switched on.

The headlamp units of the Maybach also accommodate H7 fog lamps with the latest projection technology. The driver is able to switch these on together with the low beam headlights or sidelights to obtain special inclement weather lighting which illuminates the road verges particularly well.

The exterior lighting of the Maybach is also unmistakable by virtue of what are called side markers on the outer positions of the headlamp units and in the exterior mirrors. These additional lights in the headlamp units and LEDs in the mirror housings, which glow discreetly when low beam is switched on, characterise the appearance of the Maybach in the dark and make it unmistakable even at night.

A high-pressure cleaning system ensures that the plastic lenses of the headlamps in the Maybach 62 are efficiently and gently kept clear.

Tail lights: 528 LEDs for four functions

The engineers systematically opted in favour of modern LED technology for most of the rear lighting functions. A total of 528 light-emitting diodes make their presence seen when the brakes are applied, or as indicators, tail lights and fog lamps. Only the reversing light has modern HPS bulbs with an output of 24 watts.

There are many good reasons for using LED technology. One of the most important is the very small space required by light-emitting diodes. It has therefore been possible to distribute the LEDs for the tail lights evenly over the entire surface of the rear light cluster to achieve uniform illumination well into the side areas. Accordingly the light from each tail light extends from the flanks of the bodywork almost to the middle of the rear end, and represents another lighting feature by which the Maybach may be recognised.

The third braking light on the parcel shelf and the side indicator repeaters in the exterior mirror housings are likewise equipped with LEDs. The mirror housings also incorporate courtesy lights, which are switched on when the door is opened and illuminate the entry area.

Lighting functions: automatic emergency and back-up lights

The lighting system of the Maybach is managed by an electronic control unit whose microchip also has various emergency lighting functions stored in its memory. Should a data link or electronic control unit develop a fault, for example, the automatic emergency function prevents failure of the entire vehicle lighting system. Likewise, if one or more bulbs important for vehicle safety should fail, other bulbs are switched on as a back-up.

Daytime driving lights, which also improve active safety by day in the opinion of accident researchers, can be programmed by the driver using the multifunction steering wheel and the central display in the instrument cluster. The low beam headlamps, sidelights, tail lights and licence plate illumination switch on automatically when the engine is started. If the light switch is in the "Auto" position a light sensor on the windscreen ensures that the vehicle lights switch on automatically in the dark. This Headlamp Assist function also relieves the driver of effort when entering a garage and in rainy or snowy conditions.

Engine

Effortless power

  • Characteristics: new twelve-cylinder with exemplary performance
  • Power: 405 kW/550 hp and from zero to 62.5 mph in 5.4 seconds
  • Turbocharged: biturbo system with sophisticated water intercooling
  • Smoothness: ultra-modern design for outstanding ride comfort
  • Transmission: Mercedes automatic transmission adapted to the high engine torque

Power, smoothness, durability - the qualities of the legendary Maybach engine of 1929 were again the key concerns during the development of the new "Type 12" engine.

The ultra-modern engine of the Maybach bears testimony to the wealth of experience and the great expertise of DaimlerChrysler in the field of developing, designing and building 12-cylinder engines; the Stuttgart car manufacturer is the world's largest producer of V12 powerplants for passenger cars.

5.5 litres displacement, twin turbochargers, peak output of 405 kW/550 hp and peak torque of 900 Nm - these are the impressive vital statistics of this unit, which has a higher power output and develops more torque than any other series-production passenger car engine in the world. They guarantee that the Maybach displays its characteristic assurance in all situations.

  • The Maybach 62 accelerates from zero to 62.5 mph in just 5.4 seconds.
  • Thanks to its high torque a sprint from 37 to 75 mph takes only 6.5 seconds.
  • The top speed is electronically limited to 155 mph; it is reached rapidly and with virtually no apparent effort.

This impressive picture is completed by superb smoothness and outstanding vibrational behaviour. These qualities are inherent design features of the new V12 engine: the V-angle of 60 degrees balances inertia forces and moments at source, without the need for special balancer shafts.

The modern "bedplate" design makes another major contribution to particularly smooth, low-noise operation: the "bedplate" consists of an aluminium plate with integral cast iron bearing brackets on the main crankshaft bearings for additional rigidity. This effectively reduces longitudinal vibrations in the engine block. In addition the sump has been isolated from the crankcase as a vibration-reducing measure.

Lightweight construction: outstanding volumetric efficiency with just 0.66 kg/kW

The crankcase of the new "Type 12" engine is of diecast aluminium, while the two cylinder head covers are of diecast magnesium and the cylinder liners are made from a lightweight, low-friction aluminium-silicon alloy which allows a weight-saving of approx. 500 grams per cylinder versus conventional cast iron liners. Other lightweight components of the twelve-cylinder engine include

  • ... fracture-split connecting rods made from high-strength, forged-steel alloy;
  • ... oil-spray-cooled pistons made from a high-quality aluminium alloy;
  • ... a weight-optimised, forged-steel crankshaft;
  • ... a sump of diecast aluminium.

Thanks to this advanced lightweight design the power unit tips the scales at just 270 kilogrammes, achieving an outstanding volumetric efficiency at 0.66 kg/kW.

Maybach 62: key engine and performance figures

Cylinder arrangement V12
Cylinder angle 60°
Valves per cylinder 3
Displacement 5513 cc
Bore/stroke 82.0/87.0 mm
Distance between cylinders 90 mm
Compression ratio 9.0:1
Output 405 kW/550 hp at 5250 rpm
Max. torque 900 Nm at 2300 - 3000 rpm
0-62.5 mph 5.4 s
37-75 mph 6.5 s
Maximum speed 155 mph
Fuel consumption*

city

extra-urban

combined

11.5 mpg

25.7 mpg

17.8 mpg

* acc. to NEDC

Emission control: three-valve technology and large catalytic converters

A camshaft in each of the two banks of cylinders controls the three valves per cylinder via low-friction roller-type cam followers. The two intake valves per cylinder have a diameter of 31 millimetres, while the sodium-cooled exhaust valve measures 35 millimetres. Each valve has a cam follower and is adjusted hydraulically.

The three-valve technology reduces thermal losses at the exhaust stage and speeds catalytic converter warm-up after a cold start. In conjunction with two large ceramic catalytic converters positioned close to the engine this has a decisive influence on ensuring that the new Maybach reliably complies with the strict EU-4 limits.

Emissions are controlled by two catalytic converters which are arranged close to the engine and each contain two ceramic monoliths. Two oxygen sensors per exhaust line - one upstream of the catalytic converter and one between the monoliths - provide the engine control unit with precise information about the fuel-air ratio and the quality of emission control. A resonator, a mixing area, two intermediate silencers and two exhaust silencers are further components of the twin-pipe exhaust system which ensure low noise emissions. The total silencer volume is 62 litres.

Torque: more than 600 Newton metres already available at 1500 rpm

The developers of the Type 12 engine were able to dispense with the camshaft adjustment system which is normally featured in other engines and which serves mainly to boost torque at lower engine speeds.

The twin turbochargers aspirate the twelve-cylinder so efficiently that the driver is able to mobilise the enormous power even at very low revs. Expressed in figures: a muscular 622 Nm of torque are already on tap at 1500 rpm, the 800 Nm mark is reached at 1800 rpm and from 2300 rpm the power unit generates its maximum torque of 900 Nm, a figure which is unique among series- production passenger cars. It maintains this up to 3000 rpm (see graph on right).

The maximum output of the V12 engine - 405 kW/550 hp - is available at 5250 rpm.
The maximum charge pressure is 1.3 bar.

 The space-saving positioning of the twin turbocharger turbines in the exhaust manifold maximises their efficiency. A wastegate control system enables the flow of exhaust gases to the turbines to be suited to the current operating point of the engine. Wastegate valves are integrated into each turbocharger and operate electropneumatically, receiving their commands from the engine control unit.

This powerful microprocessor controls all engine functions and uses a number of additional sensor data specifically to control the two turbochargers:

  • Pressure and temperature sensors in the charge air distributor are used to calculate the intake air mass.
  • A sensor in front of the throttle valve actuator registers the charge pressure.
  • Sensors upstream and downstream of the turbochargers monitor the pressure conditions so that their maximum speed is not exceeded.

Twin-spark ignition: alternating current technology with ionic current measurement

In addition the engine computer controls an advanced alternating current twin-spark ignition system whose outstanding feature is constant ionic current measurement at the spark plugs. This recognises any misfires and therefore has a major role in protecting the catalytic converters -- should the ionic current fall below a certain value the fuel injection for the cylinder concerned is automatically interrupted at once.

Ionic current measurement is supplemented with torsional vibration analysis at the crankshaft. By combining both control signals in this way the developers of the Type 12 engine have - for the first time in a twelve-cylinder unit - achieved an unprecedented degree of accuracy in the detection of misfires right across the entire load and engine speed range.

Cooling: low-temperature circuit for two water intercoolers

The compressed air flows from the turbochargers through two engine-mounted water-cooled intercoolers located on the cylinder head covers. Depending on the engine load the intake air is cooled here by up to 100 degrees Celsius, so that its temperature and density are optimised for the combustion process.

The water intercoolers are part of a special low-temperature circuit. A demand-controlled, electric circulation pump transfers the heat between the water-intercoolers and the low-temperature cooler located in front of the engine which passes the heat from the water to the cooling air.

Automatic transmission: precisely configured for the Type 12 engine

The Maybach engineers have adapted the well-proven five-speed automatic transmission of the Mercedes Benz S-Class to the high torque of the Type 12 engine with wider planetary gear sets, a larger torque converter, a new torque converter lockup program and a modified electrohydraulic control unit.

To transfer the unique maximum torque of 900 Nm efficiently the front planetary gear set was widened by two millimetres, and the central and rear gear sets by five millimetres. This also made it necessary to modify the input/output shaft, which is twelve millimetres longer in the Maybach 62 than in the Mercedes Benz S-Class. The fundamental mechanical and hydraulic features of this electronically controlled transmission remain the same, however, including the ratios and gearshift operation of the S-Class.

Maybach 62: transmission ratios

1st gear 3.59
2nd gear 2.19
3rd gear 1.41
4th gear 1.00
5th gear 0.83
Reverse gear 3.16

The propshaft and final drive of the Maybach are likewise suited to the high torque characteristics of the twelve-cylinder engine. The three-section propshaft has two bearing points, while the final drive of the Mercedes Benz S-Class has been reinforced and has a ratio of 2.82.

Touchshift: rapid gear changes

A button on the transmission tunnel trim enables the driver of the Maybach to choose between two shift programs: "S" for Standard and "C" for Comfort. In the Comfort program the number of gearshifting operations is reduced, and downshifts take place at lower speeds.

The Touchshift function of the automatic transmission offers outstanding convenience: while positions "P", "R", "N and "D" may be selected in the usual way, briefly nudging the shift lever to the left ("-") or right ("+") in position "D" allows changes between 4th and 1st. Maintaining pressure on the shift lever in the "-" direction causes the transmission to shift down by one or more gears until it finds the best possible gear in which to decelerate or accelerate the car. On downhill gradients this enables the driver to execute convenient downshifts for best use of the engine's braking effect; when accelerating, the most suitable gear for best performance can also be selected in this way.

The transmission electronics monitor this manual gear selection function and will only carry out shift commands within the permissible engine speed range. A display in the instrument cluster informs the driver of the currently selected shift program and gear stage.

continues... | Part Five
Published 2 July 2002 Melanie Carter
 

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