Engine and power transmission: Naturally aspirated eight-cylinder engine with transaxle dual clutch transmission

Eight cylinders and a displacement of 6.3 litres in a front-mid-engine arrangement, a high-revving concept, dry sump lubrication and a performance-oriented intake and exhaust system: opening the almost two-metre long bonnet of the SLS AMG affords a view of an outstanding high-performance engine. With a peak output of 420 kW (571 hp) at 6800 rpm and 650 newton metres of torque at 4750 rpm, the AMG 6.3-litre V8 unit delivers first-class performance figures. The Roadster accelerates from zero to 100 km/h in 3.8 seconds, reaches 200 km/h in 11.3 seconds and has a top speed of 317 km/h (electronically limited). The DIN kerb weight of 1660 kilograms produces an extremely favourable power-to-weight ratio of only 3.95 kilograms per kilowatt or 2.9 kilograms per hp.


The use of specific fuel economy measures has enabled a fuel consumption of 13.2 litres per 100 kilometres (NEDC combined) to be achieved. Power transfer in the SLS AMG is by a new, seven-speed AMG dual clutch transmission located at the rear axle in a transaxle arrangement. It is rigidly connected to the engine by a torque tube.

The combination of a high-revving concept and a large displacement achieves the best of both worlds: exhilarating flexibility accompanied by high torque at low engine speeds. The new AMG V8 already delivers 545 newton metres to the crankshaft at 2500 rpm, with the maximum torque of 650 newton metres on tap from 4750 rpm – more than any other naturally aspirated engine in this output and displacement class. In short, the new AMG eight-cylinder guarantees dynamic acceleration, rapid intermediate sprints and sheer driving pleasure at the highest level, or relaxed, day-to-day cruising when preferred.

Key data at a glance:

Optimum cylinder charging thanks to newly designed intake air ducting

The newly calculated, more flow-efficient design of the intake air ducting leads to a reduction in pressure losses, and the magnesium intake manifold has precisely configured resonance tube lengths. Eight velocity stacks with a length of 290 millimetres and a diameter of 51.5 millimetres supply the combustion chambers with fresh air. Behind the air filters with a volume of just under 9500 cubic centimetres there are two throttle flaps with a diameter of 74 millimetres. Their electronic adjustment is practically instantaneous: it takes only 150 milliseconds to open the two throttle flaps to their maximum. The result is exhilarating responsiveness. Two hot-film air mass sensors located behind the air filters supply the engine electronics with the necessary temperature and density data for the intake air.

One special characteristic of the V8 engine is its sophisticated valve drive, which borrows features from the powerful AMG racing engines. The 32 valves in the cylinder heads are operated by bucket tappets. Their space-saving design allows a stiff valve train and therefore high engine speeds with large valve opening cross-sections, which in turn benefits output and torque. The large intake valves have a diameter of 40 millimetres, while their opposite numbers on the exhaust side measure 34 millimetres. In contrast to a racing engine, the valve drive is maintenance-free with hydraulic valve clearance compensation.

Four continuously variable overhead camshafts

All four overhead camshafts are continuously variable over a range of 42 degrees. Both the intake and exhaust camshafts are adjusted as a function of engine load and engine speed, ensuring extremely high output and torque values as well as smooth idling and especially low exhaust emissions. Depending on the engine speed, the valve overlap can be varied to ensure an optimal supply of fuel/air mixture to the combustion chambers and efficient venting of the exhaust gases. The variable camshaft adjustment is controlled electrohydraulically, and monitored by the engine control unit.

Distinctive exhaust note with two exhaust headers

Optimised performance and an emotional sound signature: these were the requirements when developing the sports exhaust system. Exhaust headers with precisely coordinated tube lengths – a further technology transfer from motor racing – ensure a significant increase in output and torque by improving the gas cycle. The large pipe cross-sections of the newly developed twin exhaust system effectively reduce the exhaust counterpressure. Two relatively small pre-silencers on the underbody and a large, transversely installed main silencer at the rear help to ensure optimum weight distribution.

The AMG specialists attached particular importance to the sound signature of the eight-cylinder power unit, and exhaustive tests were carried out to achieve a synthesis of immediately perceptible dynamism and the long-distance qualities typical of a Mercedes. Great attention was also paid to the elimination of irritating noises, while accentuating the frequencies perceived as pleasant and typical of a sports car. Especially when the soft top is down, the engine note accentuates the emotionally appealing character of the SLS AMG Roadster. At the same time it was of course necessary to comply with the legal requirements – for example when measuring passing noise.

The two exhaust tailpipes integrated into the rear apron emit a characteristic eight-cylinder sound which tells every car-lover: here comes a genuine AMG. Two ceramic catalytic converters optimised for counterpressure and located at the firewall directly by the exhaust header, plus two metal catalytic converters on the underbody, provide effective exhaust gas aftertreatment and ensure compliance with all current and future limits such as EU 5, LEV 2 and U‑ LEV. The new AMG engine also easily meets specific requirements for the US market, such as Onboard Diagnosis II and lambda sensor diagnosis.

Dry sump lubrication to keep the centre of gravity low

One major criterion when formulating the technical concept for the SLS AMG Roadster was the installed position of the engine. The requirement was for the engine to be positioned low down and well to the rear, so as to lower the car's centre of gravity significantly and achieve a balanced weight distribution between the front and rear axles. The solution found, namely to install the eight-cylinder power unit as a front-mid engine behind the front axle, combining it with a transmission in a transaxle layout, led to an optimum weight distribution of 47 percent at the front and 53 percent at the rear.

The much lower installed position of the V8 engine is the result of a changeover to dry sump lubrication – which eliminates the usual oil sump. The dry sump lubrication system of the M159 consists of a suction pump, a pressure pump and an external 5-litre oil tank located in front of the engine. All in all, 13.5 litres of engine oil circulate around the complete system. The oil scavenging pump sucks the oil directly from the crankcase and cylinder heads, delivering it to the external oil tank at a maximum rate of 700 litres per minute. This efficient oil scavenging further improves the efficiency of the engine.

The reciprocating pressure pump conveys the oil from the external oil tank back to the engine, ensuring effective lubrication even under the high lateral acceleration forces that usually occur on racetracks. The demand-related control of the oil pressure pump is based on the engine speeds programmed into the control unit, as well as the characteristic maps for temperature and engine load. This leads to a reduction in the engine's power dissipation, and a considerable reduction in fuel consumption. Two large coolers in the front wheel arches, each with a blower fan integrated on one side, ensure that the engine oil is efficiently cooled.

Another innovation used in the engine is the so-called "gas-spring principle", where the air compressed beneath the piston as it moves down the gas-tight crank chamber is prevented from escaping. On the upstroke the rebound energy is almost completely returned to the pistons. This principle prevents flow losses. Another positive effect is the much greater rigidity of the crankcase. The gas-spring principle has enabled fuel consumption to be reduced by 1.5 percent – while increasing output by 7 kW (9.5 hp).

Outstanding strength and optimised lightweight construction also for the engine

The eight forged pistons, which are together 0.5 kilograms lighter than cast pistons, reduce oscillating masses and improve both responsiveness and flexibility. Optimum cooling of the severely stressed piston crowns is by means of pressure-controlled oil-spray nozzles in the crankcase. As another specific weight-saving measure, there are no steel liners locating the main crankshaft bearings. The crankcase of the M159 is wholly of aluminium, and around 4 kilograms lighter than its counterpart in the M156. To reduce weight even further, aluminium bolts are mainly used in the M159. This saves another 0.6 kilograms or so compared to steel bolts. The dry weight of the V8 engine in the SLS is 205 kg, producing a first-class power-to-weight ratio of 0.36 kg/hp.

As is usual in motor sports, the crankcase is a rigid bedplate design of closed-deck construction. The engine block and cylinder heads are of cast aluminium-silicon alloys (AlSi7 and AlSi17) which represent the state of the art in terms of weight, thermal and mechanical resistance and long-term strength. As in the M156, the engine specialists at Mercedes-AMG use a particularly advanced process for the eight cylinder walls to produce a tribologically optimal surface, the so-called NANOSLIDE technology. The advantages are extremely low friction and wear accompanied by outstanding long-term durability. A considerably harder surface is achieved compared to conventionally coated cylinder walls.

Cooling module of weight-optimised design

The coolant is cooled by a large cooler module located behind the radiator grille. The condenser for the air conditioning and the cooler for the steering servo fluid are also integrated into this module. As a particular bonus, this weighs around 4 kilograms less than conventional components – while improving efficiency at the same time. A large suction fan located directly behind the radiator conducts the hot air away as required.

Efficient control unit for generator management

The Bosch ME 9.7 AMG control unit also has a generator management function as a further system that helps to save fuel. Sensors monitor the charge status of the vehicle battery, and reduce the output of the generator if the battery has sufficient charge. The system uses the overrun phases of the engine to recharge the battery, braking energy being converted into electrical energy by recuperation.

Careful combination of efficiency-enhancing measures has enabled an NEDC combined fuel consumption of 13.2 litres per 100 km (premium petrol) to be achieved. This is an outstanding figure, as the new SLS AMG is after all one of the most powerful cars in the super-sports car segment.

Engine production at the Affalterbach plant

The new V8 powerpack for the SLS is produced in the ultra-modern AMG engine shop, on the "One man, one engine" principle. This means that a single technician assembles the engine by hand from start to finish – as witness the high-quality AMG engine plate bearing the signature of the technician responsible. The design of the AMG eight-cylinder is also a feast for the eyes, starting with the new, titanium grey cover of the magnesium intake manifold with its two prominent AMG logos, and the optional carbon-fibre engine compartment cover that frames the high-performance power unit so attractively.

AMG seven-speed dual clutch transmission with RACE START

The ideal partner for the powerful, naturally aspirated eight-cylinder engine is the AMG SPEEDSHIFT DCT 7-speed sports transmission – a dual clutch transmission with seven gears, four driving modes and a RACE START function. The advantages of this technology, which is once again derived from motor racing, include highly responsive gearchanges without any interruption in tractive power, a tailor-made control strategy and improved gearshifting comfort. Specifically configured for the high-revving nature of the AMG 6.3-litre V8 engine, the AMG SPEEDSHIFT DCT 7-speed sports transmission provides optimum ratios with only small rpm changes. In short, the new transmission gives the driver even more dynamic acceleration for maximum driving pleasure.

AMG DRIVE UNIT with four driving modes for maximum pleasure

The central control point for the AMG SPEEDSHIFT DCT 7-speed sports transmission and all dynamic control functions is the AMG DRIVE UNIT. The rotary electronic control for selection of the four driving modes and activation of the RACE START function is located to the left of the E-SELECT shift lever.

The dual clutch transmission allows upshifts under full load both in automated and manual mode, where the gears can be shifted using the AMG shift paddles on the steering wheel. There is a choice of four driving modes for maximum driving pleasure and comfort: "C" (Controlled Efficiency), "S" (Sport), "S+" (Sport plus) and "M" (Manual). In Controlled Efficiency mode the high torque already available at low engine speeds is used to shift up to the highest viable gear. The resulting dethrottling effect on the intake side lowers fuel consumption, with accompanying benefits in terms of engine noise. Controlled Efficiency also means comfortable gearchanges and "soft" accelerator characteristics for relaxed cruising.

In "S" mode the transmission remains in each gear to a higher speed, downshifts are faster and gearshifts are performed around 20 percent more rapidly than in "C" mode. Switching to "S+" mode shortens gearshift times by a further 20 percent, while "M" is the most sporty mode of all: the AMG 6.3-litre V8 engine now responds with even more "bite", and the AMG dual clutch transmission changes the gears another 10 percent faster – a total reduction of 50 percent compared to "C" mode. In "M" mode the transmission performs gearchanges in less than 100 milliseconds. The upshift indicator integrated into the AMG instrument cluster informs the driver when a manual gearchange is advisable: seven LEDs coloured white, yellow and red indicate the necessary action. The faster the engine speed approaches the maximum of 7200 rpm, the more LEDs light up.

Best possible traction thanks to the RACE START function

The RACE START function delivers maximum dynamism: in order to use it, the driver has to activate the ESP® Sport function while the vehicle is at a standstill, and press the brake pedal with his left foot. Having preselected the RACE START program using the rotary switch, the driver is presented with a confirmation message in the AMG central display. After confirming the RACE START function by pulling the "Up" shift paddle once, all he has to do is depress the accelerator fully and take his foot off the brake. The optimum start-up engine speed is set fully automatically, and the SLS AMG accelerates away with flawless traction – all the way up to top speed if required. The driver does not need to shift the gears manually, as the DCT transmission performs lightning-fast gearchanges.

Automatic double-declutching function for even more emotional appeal

In the "S" (Sport), "S+" (Sport plus) and "M" (Manual) modes, the automatic double-declutching function is active. Every manual or automatic downshift is accompanied by precisely metered double-declutching – incrementally from "S" through "S+" to "M". This not only adds to the driver's emotional experience: the load-free downshift minimises load-change reactions, which pays dividends – particularly when braking into a bend on the racetrack – and also enhances safety in the wet or on ice.

The AMG dual clutch transmission excels with compact dimensions and a low weight of only 136 kilograms, including the differential - thanks to aluminium construction. The absence of a conventional torque converter improves efficiency and makes a significant reduction in fuel consumption possible. A mechanical, multi-plate differential lock configured for sporty performance at the physical limits is also integrated into the transmission housing.

Torque tube with carbon-fibre drive shaft

The torque tube turns the AMG SPEEDSHIFT DCT 7-speed sports transmission and the V8 engine into a fixed unit. The engine and the transmission installed in a transaxle arrangement at the rear axle are firmly connected with very low flexural and torsional flexibility, and support each other. This has decisive advantages in terms of handling dynamics and driving comfort, as this sophisticated solution makes it possible to eliminate much more free play from the entire powertrain. The 1.64-metre long torque tube consists of a one-piece sand-cast aluminium housing, and weighs less than 25 kilograms. A drive shaft rotates at engine speed inside the housing. As in the Mercedes-Benz C-Class DTM racing touring cars, the shaft is made from carbon-fibre. One of the key advantages of this high-tech material is that despite its high strength, the shaft tips the scales at only 4.7 kilograms. This means that the 1.71-metre long drive shaft, which is required to transfer no less than 650 newton metres of torque from the engine to the dual clutch transmission, is around 30 percent lighter than a steel version would be.

A specially developed torsional damper is also active within the torque tube. This reliably eliminates resonances and vibrations, thereby optimising ride and noise comfort.

The new Mercedes-Benz Actros is the very first truck to receive the newly-premiered Blue Efficiency Power units that fully comply with the stringent Euro VI emission standard. These diesel engines boast excellent technical characteristics, low fuel consumption, exemplary robustness and longevity and provide high levels of output and torque across a wide range of rpm. Engineers have also mastered the X-PULSE, a new commonrail system with pressure booster, and a powerful and dynamic three-stage engine brake. Furthermore, the new powerplants feature efficient emission control solutions: the SCR technology, exhaust gas recirculation and the particulate filter. Power is sent to wheels thanks to the introduction of the third generation of Mercedes-Benz PowerShift fully-automated transmissions, tweaked for faster and more effective gear shifts.


The launch of the new Mercedes-Benz Actros heralds the arrival of a completely redesigned range of heavy-duty engines which set new standards in many respects. The new Mercedes-Benz BlueEfficiency Power engine generation has been developed specifically for use in Europe and, from the outset, will meet Euro VI requirements. The first member of the new engine family to be in the spotlight is the Mercedes-Benz OM 471 six-cylinder in-line unit, with an output range that covers the bulk of European long-distance-transport requirements. The OM 471 counters the unavoidable extra expense for Euro VI by incorporating state-of-the-art technology. As a result, the new Actros is not only cleaner, it also consumes far less diesel than its predecessor.

New engine already meets the requirements of the forthcoming Euro VI emissions standard
With this new engine generation, Mercedes-Benz continues its tradition as a trailblazer in terms of environmental compatibility. The OM 471 is the first engine in its class to be homologated in accordance with the future Euro VI emissions standard, so marking the start of a new era a full two years before Euro VI actually becomes law. Euro VI brings further significant reductions in, above all, nitrogen oxides and particulates in the exhaust gas.

The new Mercedes-Benz OM 471 covers an output range of 310 kW (421 hp) to 375 kW (510 hp), with peak torques between 2100 and 2500 Nm. During development of the OM 471, the Mercedes-Benz engineers were able to call upon a wealth of experience: the core design of the engine is based on the new platform used for Daimler Trucks' heavy-duty engines. These have been used very successfully since 2007 in trucks produced by Daimler's North American Freightliner brand (built by company-owned engine manufacturer Detroit Diesel) and since last year by Fuso in Japan.

BlueEfficiency Power: top class from Mercedes-Benz

Operators as well as drivers of the new Actros want powerful engines with good traction and low fuel consumption, along with high overall economic efficiency. They expect the best possible performance as well as refined, quiet running and exhaust gases that are low in pollutants. The new engine generation meets these requirements thanks to its robust construction and high-grade engineering, including four valves per cylinder, two overhead camshafts and a fully electronically controlled injection system with pressure booster that is unique in the world.
Like the Actros itself, the new Mercedes-Benz engines are top class in every respect. Top class in terms of the outstanding and innovative engine technology with exceptional economy and refinement thanks to the new, unique X-PULSE injection system. Top class in terms of excellent engine dynamics thanks to turbocharger technology. Top class in terms of low emissions thanks to the combination of SCR technology, exhaust gas recirculation and a particulate filter. And top class in terms of the powerful, new engine brake. Not to mention the new engines' serviceability and durability.

A wealth of output and torque variants

The Mercedes-Benz OM 471 is available with a choice of four outputs and torques for the new Actros. These configurations are suitable for typical European application conditions and meet operators' and drivers' requirements. The following versions of the Mercedes-Benz OM 471 are available for the new Actros:

Output (kW) - Output (hp) - Torque (Nm)
310 - 421 - 2100
330 - 449 - 2200
350 - 476 - 2300
375 - 510 - 2500

One of the particular highlights of the new OM 471 is the fact that, if the standard rear-axle ratio of 2.611 is specified, 200 Nm of extra torque are provided when the automated transmission is in top gear so as to prevent downshifts when driving uphill.

BlueEfficiency Power: high torque even below 1000 rpm

The rated engine speed of the new engines is set at 1800 rpm for all output variants, with the maximum torque available at just 1100 rpm. But these figures can only be a guide: as a result of the very steep output curve immediately before the main operating range, most of this maximum torque is already available at an engine speed of just 1000 rpm. Even below 1000 rpm, the torque is surprisingly high. This results in an extension of the usable engine speed range at the bottom end – down to around 800 to 900 rpm, depending on the route profile – with a correspondingly positive effect on fuel consumption.

Excellent driveability: high output across a wide rpm range

The same is true of the output curve: even at 1400 rpm, the engines deliver almost 100 percent of their full output. In reality, on the road, the output and torque curves combine to ensure excellent driveability with a high output in all key engine speed ranges. The Mercedes-Benz OM 471 reinforces this sense of dynamism with its quiet, smooth running, which is nevertheless characterised by the brand's hallmark sonorous and distinctive sound.

Compact six-cylinder in-line engine

The design of the new Mercedes-Benz OM 471 is based on six cylinders mounted vertically in-line – a platform that bodes well for the smooth running of the engine. The long-stroke design of the Mercedes-Benz OM 471, which has a bore of 132 mm and stroke of 156 mm, gives it excellent pulling power. The engine is categorised in the heavy-duty class for heavy-duty commercial vehicles. The dry weight of the Euro VI version is 1146 kg, while the weight to DIN 70020-A is 1126 kg.

Exemplary robustness and longevity

In order to meet the demands made of the new Actros class of high-powered heavy-duty trucks, exceptional robustness and durability are among the outstanding characteristics of the engine. The crankcase, for example, is made of a grey-cast-iron material developed and patented specifically for this engine generation and includes vertical structures and ribbing to make it very rigid. This design also reduces noise emissions.

The single-piece pistons, made from steel to maximise their service life, each feature two compression rings, an oil control ring and splash-oil cooling. A protective coating ensures that the engine will perform under load, even while it is being run-in. The almost negligible distortion of the pistons and the rigid crankcase keep oil consumption and blow-by losses to a minimum – so reducing costs and improving environmental acceptability. The fine plateau honing of the cylinder liners likewise reduces oil consumption as well as friction losses.

Optimum engine cooling is ensured by wet cylinder liners. The main cooling flow circulates around the upper third of the liner, while a secondary flow cools the lower section, which is not subject to such high temperatures. In general, the distances travelled by the coolant are kept short, making the cooling process here very efficient. The cooling thermostat is located at the intake end to ensure precise control. Larger radiators with a higher output reduce the thermal load whilst the fan does not have to operate as frequently, thus reducing fuel consumption.

Smooth running and an extremely rigid design

The "cracked" connecting rods are split at the connecting rod eye. In this process, the connecting rods are broken at a defined point, producing an extremely robust, close-fitting join with a large surface area when they are screwed back together. A precisely balanced seven-bearing crankshaft ensures exceptionally smooth running of the engine.

The highly rigid crankcase, steel pistons, and reinforced connecting rods and bearings were selected with the high engine ignition pressures in mind. To maximise efficiency, these have been increased from their previous level of 180 bar to over 200 bar.

The turbocharger, starter motor and crankcase ventilation system are all located on the hot side of the engine, while the engine control unit, the oil coolant module with filter and coolant pump, the fuel pumps for the high- and low-pressure system, and the consumption-optimised two-cylinder air compressor with on-demand control are grouped together on the cold side of the engine for ease of maintenance.

Exceptionally robust cast-iron cylinder head

The one-piece cylinder head for the new engine is made of grey cast iron with vermicular graphite (also known as CGI). It is exceptionally robust and designed for the high ignition pressures in the new engines.

Efficient gear drive, double overhead camshafts

At the front end of the engine, poly-V-belts drive the alternator, the coolant pump, the refrigerant compressor and the fan. The now closed-loop coolant pump is only activated as and when needed so as to reduce fuel consumption.

The extremely compact and rigid gear drive is located at the engine's output end, where it operates exceptionally efficiently, quietly and smoothly. Each of the camshafts controls two intake and exhaust valves arranged vertically in the cylinder head via low-friction rocker arms mounted in friction bearings. Rather than being milled from a solid piece of material, the camshafts are of "composite" or "assembled" design – a premiere for engines of this size – and are based on a hollow construction to save weight. They are mounted in a die-cast aluminium camshaft frame with seven bearings.

X-PULSE: unique common-rail system with pressure booster

One of the key aspects of the new engine generation for the new Actros is clean and efficient fuel combustion based on a flexible, fully electronically controlled common-rail system. Flexible in this case means that not only can the injection pressure, timing and quantity of fuel injected be varied, but also the injection rate, thanks to the new X-PULSE injection system with pressure booster that has been developed exclusively with Daimler Trucks.

Maximum injection pressure of 2100 bar

In the X-PULSE common-rail system with pressure booster, the twin-piston high-pressure pump produces a maximum pressure of around 900 bar in the common rail. This pressure is then boosted to up to 2100 bar in the individual injectors. The X-PULSE pressure booster can be varied on the engine map and adjusts continuously to the current engine operating conditions – for example to the demand for torque from the accelerator pedal. The engine control unit manages the injection point, injection quantity, injection rate, number of injections and injection pressure separately for each injector, enabling it to even out any differences between the various cylinders.

Pilot, main and post injections

X-PULSE allows an exceptionally high maximum injection pressure to be achieved as well as enabling free adjustment of the pressure and pressure distribution during main injection by means of two solenoid valves. As all the parameters are variable, each individual injection can be precisely adjusted to the specific situation.

Smooth running, economical, clean: main injection rate can be freely shaped

Many different forms of injection are possible with the new X-PULSE injection system. Their use depends on various parameters, such as the engine load: injection without pressure boosting but with just the pressure in the rail, injection with very early pressure boosting ("square" injection rate) or injection with late pressure boosting ("boot" rate). A variant in between ("ramp" rate) is also possible.

All in all, this means that for the first time it is possible to control fully the injection sequence at each engine operating point. As the highest pressure is only produced actually inside the injectors, the injections are exceptionally stable. In the case of the new Mercedes‑Benz engine generation, this results in quiet and smooth running with a high level of refinement, extremely low fuel consumption and minimal exhaust emissions.

Swirl-free turbulence, efficient combustion

The injection process takes place in a geometrically optimised combustion chamber with a shallow piston recess. The X-PULSE injector is positioned vertically and centrally between the vertically arranged intake and exhaust valves. It features an injection nozzle with seven injection orifices designed as miniature blind-orifice nozzles. The high maximum injection pressure and extremely fine fuel atomisation in the combustion chamber are the keys to efficient combustion. The combustion chamber is shaped to prevent swirl and tumble and to make the combustion of the fuel/air mixture as efficient as possible. The engines' relatively high compression ratio of 17:1 is also aimed at maximising economy.

Asymmetric exhaust gas turbocharger

The new Mercedes-Benz OM 471 has a turbocharger with an asymmetric turbine housing and fixed geometry as well as an intercooler. The asymmetric flow is an advantage, as the exhaust gases from the first three cylinders go directly through the exhaust gas recirculation system to the turbine without any losses. This process improves engine response.

Powerful and dynamic three-stage engine brake

Superb efficiency is one of the key characteristics of the new Mercedes-Benz OM 471, and this is also true of the engine brake. Mercedes-Benz uses a turbocharged decompression brake, which operates extremely effectively and quietly. The fast response time of less than 150 milliseconds is also remarkable.

The engine brake is controlled in three stages through the steering column stalk. In the first stage, the engine brake is activated on three of the cylinders. The remaining three cylinders are then activated in a second stage. In the third and highest stage, the EGR valve and wastegate are activated to increase the engine's charging level and so achieve the maximum brake power of 2300 rpm at 400 kW (544 hp). In addition to this manual actuation, the engine brake is also used in cruise control mode.

Motor control module MCM: everything under control

As the engine's "brain", the MCM (motor control module) is not only responsible for translating the demand for power governed by the driver's foot on the accelerator, but also for controlling and monitoring all the engine functions, from the start and rate of injection through to actuation of the engine brake.

By way of example: in order to achieve perfect synchronisation during gear changes, the engine needs to reach the requisite nominal speed as quickly as possible. To do so, it is even possible to fire individual cylinders whilst other cylinders are being decelerated by the engine brake. Very fast and smooth gear changes are therefore possible.

The control module uses sensors to constantly check factors such as oil level, the position of crankshaft and camshafts, the pressure in the common-rail system and the injectors, the turbocharger turbine speed, the temperature of the engine oil, coolant, fuel and charge air, the charge pressure, and the exhaust gas recirculation rate. As a result of this extensive monitoring, the engine always operates in its optimum range – the prerequisite for good performance, low fuel consumption, a long service life and low exhaust gas emissions.

Efficient emission control: SCR technology, exhaust gas recirculation, particulate filter
Conscious of the stringent requirements imposed by the Euro VI emissions standard, Mercedes-Benz has developed a combination of SCR technology with AdBlue insertion, cooled exhaust gas recirculation (EGR) and a particulate filter for the new BlueEfficiency Power engine generation in the new Actros. This solution has already proved successful on the road in commercial vehicles from Daimler Trucks on other continents. However, the configuration here is adapted specifically to comply with European emissions legislation, while the particulate filter, including its regeneration strategy, is also a special European development. All of the systems combine to ensure extremely efficient emission control.

The differences between the optionally available Euro V versions and the standard Euro VI variant include the omission of the particulate filter, a reduced recirculation rate in the EGR system and a smaller EGR cooler. To meet customer demand, there are also EEV variants in the line-up. These are based on the Euro V version. EEV and Euro V versions are available with a choice of three power outputs: 310 kW (421 hp), 330 kW (449 hp) or 375 kW (510 hp).

Low fuel consumption despite Euro VI: a milestone in engine development

Along with a high level of environmental compatibility, one of the key aims during the development of the new engine generation was to minimise lifecycle costs. First of all, this involves low fuel consumption. Despite the added complexity that was necessary to meet the requirements of the Euro VI emissions standard, these versions of the Mercedes-Benz OM 471 boast exceptionally low fuel consumption and achieve record figures in all versions of the new Actros. AdBlue consumption is also reduced drastically in the Euro VI versions.

The Euro V version of the OM 471 has even lower fuel consumption. It has a lower exhaust gas recirculation rate and dispenses with the particulate filter.

Exceptionally long service intervals ensure low lifecycle costs

At the same time, the developers have been concentrating on keeping maintenance costs down. The service intervals have now been extended to up to 150,000 kilometres, the precise figure depending on the vehicle type and its usage profile. This interval is an exceptionally good figure for an engine with exhaust gas recirculation. In reality, this means the new Actros models in many long-distance transport fleets will require just one annual maintenance call with an engine oil change. The generally maintenance-free particulate filter in the new Euro VI Actros only needs to be changed after 450,000 km and subsequently cleaned after every 300,000 km. The service interval for the air filter in the new Actros is likewise 300,000 km.

The excellent serviceability of the new engine generation also helps to reduce operating costs. A filter module fitted to the cold side of the engine includes the oil filter as well as the filter module for the fuel supply, itself comprising prefilter, main filter and the water separator for the fuel system, grouped closely together in an easily accessible position. The oil refill point is also accessibly located on the cylinder head cover – although the low oil consumption of these engines means that, in reality, the oil will only rarely need refilling.

Mercedes PowerShift fully-automated transmission

In all versions of the new Actros, the power is sent to the wheels through a Mercedes-Benz PowerShift G211 or G281 fully-automated transmission. These transmissions have already proven successful in the predecessor models. And they now offer even faster and more precise response thanks to their highly sensitive shift sensors. The ratios of the twelve-speed transmissions have been optimised for the new engines, the direct ratio in top gear serving as a basis for highly economical long-distance driving. As was the case with the predecessor, application-oriented extra functions such as EcoRoll mode, rocking mode and power mode make the driver's job easier.

New functions for transmission individualisation

New features include a crawler function in place of the previous manoeuvring mode. As in a passenger car with an automatic transmission, the clutch closes when the brake pedal is released. So the new Actros can now be driven at walking pace with a gear engaged but without the need to press the accelerator – making the driver's job even easier when stuck in traffic or when manoeuvring.

Likewise new is the range of freely selectable application-oriented drive programs. The Economy Drive package, installed as standard, offers the driver the already economical Standard drive program as well as an Economy program for significantly reducing fuel consumption on the road. The Economy program does not use kickdown, while the EcoRoll function cannot be deactivated, and the top speed is limited to 85 km/h. The optional Power Drive package includes the fuel-saving Standard program as well as a Power shift program which offers the driver optimum performance. Furthermore, this program allows a GCW of up to 120 t in heavy-duty applications. These individualised shift programs mean that the Actros can be ideally adapted to the particular application conditions.

Faster gear change, controlled by the steering column stalk

Another factor behind the top performance achieved by the new Actros is even faster gear changes with less loss of road speed, which has a positive effect on both average road speed and fuel consumption.

The transmission controls are also new: as every new Actros is supplied with a fully-automated transmission, a steering column stalk is now provided – for the rare occasions on which the driver has to intervene manually.

Tried-and-tested axles, longer ratios

The new Actros is available exclusively with fuel-saving hypoid axles. Although the tried-and-tested HL6 axle from the predecessor has been retained, it now has a new hypoid gear to reduce friction losses. This improvement in efficiency is reflected in lower fuel consumption.

The new high-torque engines with a far wider usable speed range and the "Top-Torque" torque increase in top gear combined with the optimised Mercedes PowerShift with shorter shift times allow a longer rear axle ratio to be used. The standard ratio for semitrailer tractors is now i=2.611 rather than i= 2.846 with a correspondingly lower engine speed level. At a speed of 85 km/h in twelfth gear, the engine in the new Actros runs at just 1260 rpm rather than 1370 rpm – another factor behind the lower fuel consumption achieved by the new Actros.

Furthermore, Mercedes-Benz has extended the range of available rear axle ratios once more. There are now five versions of the HL6 rear axle available for semitrailer tractors with a standard frame height and 315/70 R 22.5 tyres, ranging from i=2.533 to i=3.077. There are also five versions available for lowliner versions with 295/55 R 22.5 tyres, ranging from i=2.2278 to i=2.733.

Economy Packs: economical miracles in package form

If a fleet's main priority is maximum economy, Mercedes-Benz makes it easier to select the right components by offering ready-made Economy Packs at attractive prices. The Classic Economy Pack includes a tyre pressure monitoring system, wind deflectors and side panelling, while the Top Economy Pack also includes a retarder.

FleetBoard and service contracts further boost cost-effectiveness

It's not just the vehicle technology in the new Actros that boosts cost-effectiveness, telematic systems do their bit, too: FleetBoard is included as standard for the first time. The FleetBoard vehicle computer is fitted as standard on board every new Actros. The extensive FleetBoard services can be used free of charge for the first four months. Only after this period does a fee become payable, should the customer decide to continue using FleetBoard. FleetBoard services include trip recording, driving analysis, telediagnosis and maintenance management. What's more, the driver – and only the driver – receives short-time analyses of his or her driving style from the trip computer on the instrument panel display as part of FleetBoard EcoSupport. FleetBoard makes it possible to cut costs by five to 15 percent.

Customised service contracts likewise help to boost the cost-effectiveness of the new Actros. Given the longer service intervals, these are notably less expensive.