2002 Maybach 62

Effortless power

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 engine of the Maybach saloons 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 Newton metres – 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 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 power-to-weight ratio with just 0.66 kg per kW

The crankcase of the new "Type 12" engine is of die-cast aluminium, while the two cylinder head covers are of die-cast 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 as compared with 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;

• ... hollow-bore camshafts of inductively hardened forged steel

• ... a weight-optimised, forged-steel crankshaft;

• ... a sump of die-cast aluminium.

Thanks to this advanced lightweight design the power unit tips the scales at just 270 kilograms, achieving an outstanding power-to-weight ratio at 0.66 kg/kW.

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 front silencer, a mixing area, two intermediate silencers and two rear 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 Newton metres of torque are already on tap at 1500 rpm, the 800 Newton metre mark is reached at 1800 rpm and from 2300 rpm the power unit generates its maximum torque of 900 Newton metres, a figure which is unique among series-production passenger cars. It maintains this up to 3000 rpm. 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 turbochargers 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 ion sensing

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

Ion sensing 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 air/water intercoolers

The compressed air flows from the turbochargers through two engine-mounted air/water 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 air/water intercoolers are part of a special low-temperature circuit. A demand-controlled, electric circulation pump transfers the heat between the air/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 Newton metres 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.

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.

On the safe side

Everything under control