Mercedes Benz
Series 47x (OM 470-473)
stroke	145/156/163/171 mm
design	Inline six-cylinder 4 valves (2 E / 2 A)
valve train	2 overhead  camshafts ( DOHC )
compression  ratio	17.0: 1
cooling	water cooling
fuel	Diesel min. 51CZ
Fuel  treatment	Common Rail -  direct injection
emission standard	EU 5, EEV, EU 6
charging	Turbocharger with  asymmetric air supply or Turbocompound technology
application	Commercial vehicle engine , built-in  engine
predecessor	OM 540 series
range of services
OM 470-473	240-460 kW  (326-625 hp)

The OM 47x engine family , which was completely redeveloped by Mercedes-Benz , consists of a total of four different engines and represents the current expansion stage in the line-up of Mercedes-Benz commercial vehicle engines. All designed as long - stroke inline six - cylinder engines , the individual engines only have one another Differences in terms of bore and stroke on. Two types of engine each rely on a uniform modular system with regard to important components ( pistons , connecting rods, Fuel processing etc.) back. A special feature of the new engines is the soft and quiet engine, which is achieved primarily by the high-pressure common-rail - direct injection . In addition to acoustic advantages, the series construction offers the advantage of a high mechanical balance (largely vibration-free) due to the very good mass balance.

Like its predecessors, the OM 47x series also follows the usual nomenclature of Mercedes-Benz engines, whereby the letter sequence OM stands for oil engine (ie diesel engine).  The new generation of engines replaces the previous V-engines in the Mercedes-Benz Actros ( OM 541 V6 and OM 542 V8 ) and the six-cylinder OM 457 (h) LA of the Mercedes-Benz ( Citaro - Tourismo - and Travego -) and Setra - (Series 400) buses and OM 460 LA , which, for. B. in some models of the German agricultural machinery manufacturerClaas (models Jaguar and Xerion ) is used.

Since December 2007, three of the four largely developed under the auspices of Stuttgart engine series were by the US subsidiary Detroit Diesel introduced and run there since then as DD13 (OM 471, presented 01/2009) DD15 (OM 472; 12/2007) and DD16 (OM 473; 12/2009) from tape. In March 2010, Daimler's Japanese subsidiary Mitsubishi Fuso Truck and Bus (MFTB) began converting to the 6R10 (OM 471). The production takes place in the plants Mannheim and Redford (USA). Various components are each manufactured centrally in one factory to achieve maximum economies of scaleand then exchanged with each other. For example, the Mercedes-Benz Mannheim plant produces the world's demand for camshafts, while all connecting rods are manufactured at Detroit Diesel in Redford. The engines for Mitsubishi Fuso are largely completely manufactured in Mannheim and completed in Kawasaki (Japan). In Mannheim cylinder heads and engine blocks are cast, while the subsidiary Atlantis Foundries in Cape Town ( South Africa ) pouring the cylinder crankcase for the North American market. Structurally, German, US and Japanese versions differ in more than 200 components, u. a. regarding the injectors, Turbocharger, control electronics and the air compressor . 

The earlier use in the USA and Japan is due to the stricter emission standards that apply there ( US EPA 10 and JP09 , the latter currently being the strictest emission standard worldwide). To date, around 70,000 OM 47x engines have been sold in the US and Japan. Overall, the motors have several million test kilometers (a total of about 50 million) on the road and the engine test standbehind. The use in Japanese and US vehicles also made it possible to consider drivers' experience with regard to the design of their German counterparts. Compared to the previous series 500, the stability increased by 20% to 1.2 million kilometers (without basic overhaul). The maintenance intervals have been extended to now 150,000 kilometers.

The interpretation as a world engine has the widespread use of modern series result. While the two largest engines are reserved for the new Actros truck (and for the US and Japan, the corresponding Freightliner , Western Star and Mitsubishi Fuso Trucks), the two smaller inline six-cylinder models will also be available in several other Mercedes-Benz commercial vehicles , such as in the new model series for the heavy distribution traffic Antos ,the successor of the series Axor , are used. After announcement of the Daimler AG , which presented in May 2011 new bus Citaro  is already prepared for the mandatory from 2012 Euro 6 standard, is that since May 2012 the engine series OM 936 (7.7 liters) and OM equipped 470 (10.7 liters). Eben Such is true for the Travego (the coach of MB) and the current Setra -500 series, which includes the lines, buses and coaches. In these types since Euro 6 duty come the engines OM 470 and OM 471 used. Up to Euro 5 standard, the OM 457 LA series (11.97-liter straight-six with pump-line-nozzle injection) was used in the aforementioned buses .

All designs are the same as the basic design of the crankshaft housing, the crankshaft , the cylinder head with four (4) vertically suspended valves per cylinder (24-valve) and the valve train with two (2) overhead camshafts ( DOHC ). For the rigid one-piece cylinder head, Mercedes-Benz relies on the gray cast iron material with vermicular graphite, which was specially developed for the long-stroke straight-six(MB patent). This new material allows a particularly high stability and rigidity. Necessary is the higher strength also due to the increased compared to its predecessor ignition pressures. In favor of a higher efficiency these are from 180 to now max. Increased to 230 bar. 

The turbocharger , crankcase breather and starter are mounted on the hot side of the engine, while the air compressor , engine control and fuel pumps for high and low pressure system and oil coolant module with filter and coolant pump have been placed on the cold side. On the front of the engine there are three poly-V belts in different planes, which serve to drive the alternator , the cooling water pump, the hydraulic fan and the air conditioning compressor . The design of the levels is configuration-specific, with the third level for the drive optional Ancillaries is available. On the output side of the engine, there is the gear drive , which drives the oil pump, the common-rail high-pressure pump, the optimized two-cylinder air compressor, the power steering pump and the two overhead camshafts.

In contrast to the predecessor series OM 501 LA (11.95 liter V6) and OM 502 LA (15.93 liter V8), this is noticeably higher in the new OM 47x series. While the old V6 weighs only 885 kg, the 471 now weighs 1,156 kg. The larger OM472 weighs 1,306 kg and the equivalent OM 502 V8 weighs approximately 1,125 kg. 

The OM 47x was able to prove the lower fuel consumption mentioned by Troska. The Actros 1845 (OM 471 with 330 kW / 449 hp) with a StreamSpace cab (2,500 mm wide) consumed an average of 7.6% (Euro 5 version) on a 10,000 km long commute run between Rotterdam and Szczecin 25.1 liters of diesel) or 4.5% (Euro 6; 25.9 liters) less diesel fuel than its direct predecessor, the Actros 1844 MP 3 LS (L cab) with the V6 cylinder OM 501 LA III ( 320 kW / 435 hp, consumption: 27.1 liters). Similar to the current Mercedes-Benz passenger car engines, the OM 47x series also carries the suffix BlueEfficiency Power, which points to low fuel consumption and exhaust gas purification with the help of AdBlue.

The higher weight of the new series is compensated in part by the restructuring of the engine program. In the future, the largest expansion stage of the OM 471 (375 kW / 510 hp) will replace the smallest eight-cylinder engine. The following table provides information about the available versions.

The individual motors at a glance 

The smallest engine of the new series is the OM 470 (dry weight 990 kg), which covers the output range between 240 kW / 326 hp and 315 kW / 428 hp at just under 10.7 liters. Above ranked the OM 471 with 12.8 liters. The engine, which was presented to the public in March 2011, is available in power classes from 310 kW / 421 hp to 375 kW / 510 hp. The 14.8-liter OM 472 covers the power range for which the 15.9-liter V8 of the OM 502 series was previously responsible: 400 kW / 544 hp to 448 kW / 615 hp. The largest member of the new engine family is the OM 473, a 15.6-liter engine offering power up to 500 kW (680 hp) for heavy duty applications. All engines are in Euro-6In addition, some variants of the OM 471 also with Euro 5 standard or in EEV certification, a legally not yet set homologation . 

Overall, the OM 47x uses several new features:

One of them is the assembled camshaft, which, unlike the predecessor series OM 457/460 and OM 501/502, is not machined from the full material. Instead, the waves are hollow and the cams are then shrunk. The process was developed around 1986 by the company Emitec / the former managing director Wolfgang mouse , but no longer pursued, since one focused on metal catalysts. The hollow camshaft is cheaper to manufacture and a few kilograms lighter. Nevertheless, the new inline six-cylinder over 200 kg have more dry weight than the previous V-six-cylinder .

Also new is the asymmetric turbocharger. To quickly build up the boost pressure and thus a rapid increase in power and torque, the exhaust gases of the cylinders four to six are passed directly into the turbine without detour. By contrast, a defined quantity of exhaust gas for exhaust gas recirculation is branched off from the exhaust gases of cylinders one to three. It serves to reduce NOx emissions. Instead of the previous EGR valve, there is now a far forwardly installed EGR valve in the exhaust manifold, well before the entry of hot exhaust gases into the turbocharger. As a result, the distribution can now be regulated steplessly and very precisely across the entire engine map, resulting in effective thermal management and a generally lower EGR rate with fuel consumption advantages.

The newly developed, asymmetric injection ensures good regeneration of the diesel particulate filter even at low load, significantly raising the EGR rate and thus the exhaust gas temperature of cylinders four to six. In comparison, the injected amount for the first three cylinders can be reduced to zero. The power output and the fuel consumption should not be affected by this reduction until the cylinder deactivation, the exhaust quality on the other hand increases and the soot particle emission decreases. If the driver steps on the accelerator pedal again and thus increases the load, the injection is automatically repeated for all cylinders evenly.

In addition, the concept of the OM 47x includes a three-stage supercharged decompression brake . In the first stage only three cylinders work, while in the second stage all six cylinders act as a decompression brake. In addition, turbocharger boosts turbocharging at the highest level, so the maximum braking power is up to 340 kW / 462 hp for the OM 470 or 400 kW / 544 hp for the OM 471. Within 150 milliseconds, the full braking power is available.

Second Generation OM 471 

On July 3, 2015, Mercedes-Benz presented the second generation of the OM 471 series to the national and international trade press, which uses some three percent less fuel than the first generation due to a few technical changes. With an annual mileage of 130,000 km, Mercedes-Benz speaks of about 1,100 liters of fuel savings.

The technical changes include u. a. the new geometry of the piston recesses, the 17.3: 1 to 18.3: 1 significantly increased compression ratio and a reduced rate of exhaust gas recirculation (EGR). All measures lead to a further improvement in the efficiency of the entire engine map.

A new air conditioning system that saves fuel, the elimination of a fault-prone wastegate valve for the turbocharger and the lack of the usual boost pressure control provide more comfort with higher reliability.

Unlike the first generation, the second is now available in five power levels between 310 kW / 421 hp and 390 kW / 530 hp. Both the power maximum and the highest torque are available almost constantly over a wide speed range in all engines of the new generation, which further improves driveability.

The new heavy-duty OM 471 diesel engine has been delivered since October 2015.

As with trucks usual engines for some time, the OM 47x is a turbo diesel - direct injection engines with four-valve technology. The fuel preparation takes place via a high-pressure injection system with multi-hole nozzles and common rail technology, which delivers a maximum pressure between 900 and 2500 bar (2nd generation OM 471 between 1160 and 2700 bar). A fuel capacity control adapted to the engine load ensures efficient use of the energy contained in the diesel fuel ( calorific value 45.4 MJ / kg at 25 ° C ).

The combustion process is divided into pilot , main and post-injection. A maximum of two pilot injections serve a gentle increase in pressure and thus lower the noise level. In the main injection, both pressure level and pressure build-up can be individually adjusted with the help of two solenoid valves . A post-injection makes it possible, if necessary, the extensive combustion of the particles or the regeneration of the particulate filter (by increasing the exhaust gas temperature). The active regeneration of the particulate filter via a separate injection valve in the exhaust port, the so-called HC Doser.

The injection pressure of the common rail system developed jointly with Robert Bosch GmbH - with pressure boosting in the injector itself - can be freely modulated and flexibly adapted to current conditions. Called "X-Pulse" (Detroit Diesel: Amplified Common Rail System ) by Mercedes-Benz , this system effectively controls the amount and timing of fuel injection based on engine operating conditions. The injection nozzle is an eight-hole nozzle (previously seven holes), which increases the maximum flow by around ten percent. The maximum rail pressure is 900 bar (2nd generation OM 471: 1160 bar), which achieves a maximum injection pressure of 2500 bar (2700 bar).

There are three different profiles available to the all-electronic Motor Control Management (MCM) : Boot (late boost), Square (early boost), and Ramp (a mixture of both). The profile boat is characterized by two successive plateaus, the former being located lower than the latter. In profile Ramp , the pressure increase takes place in two phases to reach a specific plateau. The last profile, Square , features a rectangular pressure profile that keeps the plateau level longer. Depending on the engine load and operating state, the engine control MCM decides whether the pressure boost takes place early, late or not at all. In the latter case, it remains at 1160 bar form. Together with the free-formable main injection, complete control of injection quantity and time is ensured.

Further measures to reduce fuel consumption 

Since the new Actros standard axle ratio for reducing fuel consumption is longer than previously (2,611: 1, previously 2,846: 1), the three smaller variants of the OM 471 have the Top Torque electronics, which in the largest gear additional 200 Nm torque (about 23 kW / 31 hp at 1,100 min ^-1 is) available.Thus, the motor has the speed range from 800 min ^-1 and 1400 min ^-1 more pulling power, and the driver can drive longer top gear. In addition, the asymmetrically designed turbocharger and load-controlled ancillary units (water and power steering pump) ensure even greater efficiency.

The engine brake is supported by a water retarder from Voith , which is attached to the rear of the gearbox. This runs at about twice the PTO shaft speed and achieves up to 600 kW braking power or 3500 Nm braking torque. The secondary water retarder (SWR) uses the cooling liquid (also for lubrication) instead of an oil filling, which absorbs the heat energy and delivers it via a heat exchanger to the engine cooling. The new retarder weighs about 30 kilograms less than the previous oil retarder (65 kg instead of about 100 kg).

In order to achieve the Euro 6 emissions standard, various emission reduction facilities are required for exhaust aftertreatment . To clean the exhaust gases, Mercedes therefore uses a combination of cooled exhaust gas recirculation (EGR), particulate filters and SCR technology ( Selective Catalytic Reduction ). To reduce nitrogen oxides ( NO , NO ₂ ), Daimler is relying on the 32.5 percent urea solution AdBlue, which has been in use since 2005 . By this addition (chemical catalyst), the chemical reaction can be carried out at lower temperatures. At Euro 5, on the other hand, Mercedes-Benz does not use the particulate filter and relies on a lower exhaust gas recirculation quantity. As a result, the Euro 5 variants require less cooling air to lower the temperature of the EGR system.

Smaller series OM 93x 

One year after the introduction of the OM 471, in March 2012 Mercedes-Benz introduced a new generation of four- and six-cylinder in-line engines, which will in future drive the Atego and the smaller versions of the new Citaro (C2) series. The heavy van Vario will no longer receive this engine family as its production will be discontinued for the 2014 model year. In this series increased the B10 durability by 20 percent to 750,000 kilometers (625,000 km previously).

These medium-duty engines of the OM 93x series have a displacement of 5.1 (four-cylinder, OM 934) and 7.7 liters (six-cylinder, OM 936) and are only available in Euro VI homologation . In the medium term, they will replace the current series OM 904/924 (4.25 or 4.8 liter displacement) and OM 906/926 (6.37 or 7.2 liters displacement) as part of the transition to upcoming emission standards. Like the OM 47x series, they have common-rail injection, but with up to 2500 bar injectionpressure and no X-Pulse technology. They are available in four (OM 934) and five power levels (OM 936). The dry weight (according to DIN70020-A) of the engines is 495 kg (four-cylinder) or 650 kg (six-cylinder) and thus similar to the big brother OM 47x in the class usual range. 

The series in comparison with competitors (Euro 6 standard)

Technical differences 

As a technical innovation in diesel engines , the small series has for the first time adjustable camshafts , which allows variable control of the valve times, which can also be used to regenerate the particulate filter . Opening the exhaust valves earlier will result in hotter exhaust gases entering the exhaust tract, which will drain the filter.

The maximum power range of the new engines is between 115 kW / 156 hp and 260 kW / 354 hp. In the smaller four-cylinder engines of the OM 934 to 130 kW / 177 hp series, Mercedes-Benz uses a single-stage turbocharger , while the two larger versions have a two-stage supercharger. For the six-cylinder OM 936 to 220 kW / 299 hp, an asymmetrical turbocharger with two exhaust gas flows is used; the two largest expansion stages have two of these turbochargers (biturbo). 

All four models use an electronically controlled wastegate valve, which not only limits the maximum boost pressure , but also improves the engine's response to acceleration and engine brake application .  four-cylinder OM 934 has an output between 145 kW (standard) and 170 kW (premium), and the OM 936 six-cylinder engine between 235 and 300 kW. In both cases, the operation is done via a steering column lever, which is carried out in two-stage four-cylinder and six-cylinder three-stage. 

The engines in the overview