The new engines: BlueEfficiency Power units in Euro VI for a wide range of applications
- Fuel consumption in Euro VI version up to five percent lower in conjunction with significantly improved performance
- Finely graduated range of compact four and six-cylinder engines matched to specific applications
- Effortless performance with high-torque engine characteristics
- Robust high-tech construction extends operating life by 20 percent
- Innovative BlueTec 6 exhaust gas technology with optimised AdBlue consumption and automatic filter regeneration
- Engine braking effect improved by 50 percent
- Service intervals extended to as much as 120,000 km (in long-distance haulage operations)
At the heart of the new Mercedes-Benz Atego models are two completely new BlueEfficiency Power engines with four and six cylinders respectively, delivering an output that ranges from 115 kW (156 hp) to 220 kW (299 hp). These state-of-the-art drive units combine low fuel consumption with extremely low emissions. The higher output and torque are impressive but so, too, is their significantly improved responsiveness across the full performance range.
Both the new basic engines, the OM 934 four-cylinder unit with a displacement of 5.1 litres as well as the 7.7-litre six-cylinder OM 936, have been newly developed from scratch. The advantages of developing a new BlueEfficiency Power engine series rather than further developing the existing basic engines to meet the forthcoming Euro VI standard are obvious: an uncompromising engineering focus on meeting the relevant emissions standards and at the same time on achieving optimum performance in terms of drivability, performance, economy and operating life.
While the smaller of the two engines, the OM 934, is being premiered in the new Atego, the OM 936 is already to be found in the Actros, Antos and Arocs.
BlueEfficiency Power engines from a state-of-the-art modular system
The new in-line engines score top marks in their class in every respect right from the word go. Their undisputed benchmark position has been made possible by the use of sophisticated technology that had, until now, only ever appeared in this form in the heavy-duty classes of truck. With a dry weight of less than 500 kilograms, the exceptionally weight-optimised OM 934 four-cylinder unit is, like its larger equivalent the OM 936, based on a modular system involving a significant number of common parts.
Particular features of the design, such as the composite camshafts with shrunk-on cams, forged and bolted conrods, as well as a crankshaft designed to be exceptionally rigid, reveal not only their genetic links to the large engine series but also make very clear: these engines are designed for a long, successful and efficient working life.
Savings of two percent from the engine alone
The design, involving two overhead camshafts, four valves and two intake as well as two outlet ducts, arranged in parallel in each crossflow cylinder head, marks out this new generation of engines as a highly sophisticated example of automotive engine design. In terms of output and engine characteristics, the new engines have been specifically designed to perform well across their normal operating range involving a mixture of urban and inter-city driving. High ignition pressures of more than 200 bar in conjunction with a state-of-the-art common rail injection system with an operating pressure of 2400 bar help the two Euro VI in-line engines to deliver significantly improved fuel consumption figures, with savings of two percent from the engine alone compared with the previous engines.
Variable injection timing furthermore facilitates immediate cold starting even when the temperature outside is positively arctic.
The use of newly developed sophisticated technology at every opportunity has resulted in record figures for performance, emission characteristics and economy hitherto unseen in this application class. The new solenoid valve injectors with ten-hole nozzles allow optimum injection, so that a precisely measured quantity of fuel is injected at the ideal moment into the stepped recesses of the splash oil-cooled aluminium pistons. With a specific output of up to 33.8 kW/l (46 hp/l) these new drive units, with their long-stroke configuration and cooled exhaust gas recirculation, can be counted among the most efficient of all diesel engines.The new 5.1-litre four-cylinder unit, for example, even in the entry-level version with 115 kW (156 hp), offers impressive top torque of 650 Nm, which is consistently available right across the main operating range of between 1200 and 1600 rpm. Above this, in the engine speed range from 1600 to 2500 rpm, around 90 percent of the peak output is available.
The high torque in the lower and mid engine speed range is thus complemented by the maximum output available above this point and up to the rated engine speed to ensure optimum driving power across the full operating spectrum.
Finely graduated output for the weight-optimised four-cylinder unit
The new Mercedes-Benz Atego is thus faster and more dynamic in the way it goes about its daily business, and significantly more economical as well. The light-duty truck segment demands a high level of versatility and the engine range offers a variant to suit the requirements of a multitude of different applications. A finely graduated range of BlueEfficiency Power four-cylinder units with four power ratings – 115 kW (156 hp), 130 kW (177 hp), 155 kW (211 hp) and 170 kW (231 hp), covers all the horsepower variants most commonly sought in short-radius distribution operations with either a solo unit or a light-duty drawbar combination.
The constant availability of impressive torque of between 650 and 900 Nm offered by the OM 934 at engine speeds over 1200 rpm qualifies the new Mercedes-Benz Atego as the torquiest representative of its application class. The overall performance of the new four-cylinder engine thus even manages to match the figures for the six-cylinder unit in the 900 engine series that has been available until now.
The Mercedes-Benz OM 934 is available in four output and torque categories:
115 kW (156 hp) at 2200 rpm
650 at 1200 – 1600 rpm
130 kW (177 hp) at 2200 rpm
750 at 1200 – 1600 rpm
155 kW (211 hp) at 2200 rpm
850 at 1200 – 1600 rpm
170 kW (231 hp) at 2200 rpm
900 at 1200 – 1600 rpm
Powerful six-cylinder with robust response from the lower engine speed range
Picking up seamlessly where the very compactly built four-cylinder engine leaves off comes the output spectrum offered by the 7.7-litre OM 936 six-cylinder in-line unit. With three closely graduated ratings of 175 kW (238 hp), 200 kW (272 hp) and 220 kW (299 hp) and peak torque of between 1000 Nm and 1200 Nm, the dual-camshaft engine finds its place in all important output categories relevant for light-duty distribution operations and, in some cases, even for the particularly demanding medium-duty distribution sector.
The Mercedes-Benz OM 936 is available in three output and torque categories:
175 kW (238 hp) at 2200 rpm
1000 at 1200 – 1600 rpm
200 kW (272 hp) at 2200 rpm
1100 at 1200 – 1600 rpm
220 kW (299 hp) at 2200 rpm
1200 at 1200 – 1600 rpm
Like its bigger brothers in the OM 47x engine series, the six-cylinder single-turbocharger unit relies on an asymmetric turbine. Common to all engines is the use of an electronically controlled wastegate valve to regulate the charge pressure. Precise control of the charge pressure improves engine response during acceleration as well as during engine braking.
Optimised coolant circuit
Both engine series are ideally equipped for technically demanding operations as fully fledged Euro VI units by an optimised coolant circuit that uses a cooled exhaust gas recirculation system to keep the higher operating temperatures efficiently under control. Because the water pump is now mounted on the side of the engine, while the mechanism for the valve control and oil pump has been moved further back, both these BlueTec 6 engines manage to retain the compact exterior dimensions of the predecessor units despite their larger displacement and coolant circuit.
Saving space was also a priority when it came to the emission control system necessary to comply with the Euro VI standard that comes into effect on 1 January 2014. Quite apart from the in-engine exhaust gas recirculation, this system involves an oxidation catalytic converter, a closed-loop particulate filter, AdBlue injection and an SCR catalytic converter with so-called slip catalytic converter, operated in sequence. The BlueTec 6 filter systems, compactly installed in an exhaust box, are controlled via an electronic system that regulates the emission control system as needed according to a multitude of engine and operating parameters.
The Aftertreatment Control Module (ACM) finds its counterpart in the Motor Converter Module (MCM), which is responsible for controlling all important functions of the engine from injection through to the engine brake. This extremely precise engine management system is an important factor in the improvement of two percent that has been achieved, despite Euro VI exhaust gas technology, in the fuel consumption of the BlueEfficiency Power engines compared with their Euro V predecessors from the successful and proven 900 engine series. Taking all optimisation measures into account, the new Mercedes-Benz Atego delivers a reduction in fuel consumption of up to five percent compared with its tried and tested predecessors.
Improved economy through reductions in fuel consumption
The quantity of AdBlue that needs to be injected has also been reduced by half to just 2 to 2.5 percent of the fuel consumed, thanks to the low engine emissions and the intelligent exhaust gas aftertreatment. This lower consumption also plays its part in the impressive overall economical performance of the new Mercedes-Benz Atego. The systematic focus on achieving optimised economy, in conjunction with significant improvements in performance, takes the two new BlueTec 6 in-line engines under the Atego cab to a clear benchmark position in this application category as a whole.
One example of the rigorous integration efforts made with respect to the engine and exhaust gas aftertreatment is the regeneration of the diesel particulate filter, in other words the regular burn-off of soot particles filtered out of the exhaust gas. In order to achieve this, the engine temporarily increases the temperature of the exhaust gas. An injection of fuel is then made downstream of the engine via the HC doser. In a catalytic combustion process within the oxidation catalytic converter, this fuel causes heat to be released. This in turn raises the temperature of the exhaust gas once again, taking it to the temperature needed for the burn-off of the filtered soot particles. In order to achieve this, the various measures relating to the engine (camshaft adjustment with VCP plus multiple injections to increase the temperature of the exhaust gas) and to the exhaust gas aftertreatment system (HC metering and mixing with the exhaust gas, plus selection of the surface finish and precious metal coating of the oxidation catalytic converter) have been perfectly coordinated with one another. The result: automatic regeneration of the particulate filter is possible in virtually every conceivable operating mode, even at outside temperatures as low as minus 30 degrees Celsius. This therefore practically eliminates the need for forced regeneration of the particulate filter involving the vehicle standing with its engine running – an invaluable benefit for vehicles operating in the urban distribution sector. The Atego driver can simply get on with his round, without being held up in any way by the regeneration process.
World premiere in a diesel engine: adjustable exhaust camshaft
The adjustable exhaust camshaft, or VCP (Variable Camshaft Phaser) is used here in a series-production diesel engine as a world-first. The hydraulically operated, variable camshaft adjuster allows the exhaust valves to open earlier if so required. Hotter exhaust gas escapes into the exhaust duct, thus also helping with the regeneration of the particulate filter while on the move or at outside temperatures as low as minus 30 degrees Celsius. No impact is therefore felt during driving.
A new maintenance monitor contributes to ensuring that there are fewer interruptions to productive transport work. This calculates the necessary service intervals by taking into account the specific working and operating conditions of the vehicle. In long-distance operations, it is possible for the new Mercedes-Benz Atego to run for up to 120,000 kilometres before needing its next scheduled service. This is 20,000 kilometres more than was the case for its predecessor and the best in this class. In terms of oil consumption, too, the new Atego is emphatically frugal. The sophisticated BlueTec 6 engines require only half as much lubricant as their predecessors from the 900 series.
But it is not only with their economical and dynamic traction that these latest Atego engines achieve top scores. Their engine braking performance represents a further highlight in the short-radius distribution class. Just as in the case of the larger-displacement OM 470, OM 471 and OM 473 units, the new OM 934 and OM 936 Atego engines feature a double-synchronised decompression engine brake. The four-cylinder variants offer retarding performance of 145 kW or, as an option, 170 kW. The six-cylinder models, with a displacement of 7.7 litres, can mobilise a retarding performance of 235 kW in the standard specification and as much as 300 kW in the optionally available premium variant. The maximum engine braking effect in the 93x engine series surpasses that of the constant-throttle engine brake in the previous series by some 75 percent. In the lower engine-speed range the advantages of the new system are even significantly greater. The performance of the engine brake of the new four-cylinder unit exceeds that of the Euro V six-cylinder unit, while the new six-cylinder moves into a dimension that until now has been the sole territory of large-displacement heavy-duty engines.
Use of the new engine brake has a clear positive impact on the disc brakes that are fitted on all axles, in terms both of brake lining wear and of thermal management. Compared with the previous model, the engine braking power of the new decompression brake has increased by around 50 percent, while it also helps to enhance safety and ride comfort considerably, as well as minimising wear and tear. For heavy-duty operations, where a trailer is frequently attached, Mercedes-Benz is the only manufacturer in the distribution-vehicle sector to offer a permanent magnet retarder with additional wear-free braking torque of 650 Nm. The advantage of the retarder over the engine brake, apart from the further improved retarding performance, lies in the increased comfort as a result of being able to drive at lower engine speeds.
The pronounced dynamic temperament of the new high-tech engines with their robust performance even at low engine speeds also means that longer rear-axle ratios can be applied as standard, with a concomitant positive impact on the overall economic efficiency of the vehicle. All in all, the new state-of-the-art in-line engines demonstrate overall performance characteristics that until now could only be achieved by engines with a significantly larger displacement. The new Mercedes-Benz Atego sets new standards in its class in this respect.