OM 906

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OM 906

Daimler-Benz
Damler-Benz OM 906 LA
-
Diesel
Motor	OM 906 LA	OM 906 LA II/1	OM 906 LA III/2	OM 906 LA II/3	OM 906 LA	OM 906 LA III/4	OM 906 LA III/3
Variant	906.940	906.910 906.920 906.922	906.915 906.925 906.927 906.951	906.911 906.921 906.923	906.941	906.916 906.926 906.928 906.952	906.939
Byggeår
Ytelse (HK)	231 @ 2300	231 @ 2300	231 @ 2200	280 @ 2300	280 @ 2300	280 @ 2200	245 @ 2200
Dreiemoment (Nm)	810 @ 1300	810 @ 1200 - 1500	810 @ 1200 - 1600	1100 @ 1260 - 1500	1100 @ 1300	1100 @ 1200 - 1600	1100 @ 1260 - 1500
Vekt tørr (Kg)
Innsprøytning	Injektor
Sylindre	R6
Slagvolum	6374 cm³
Borring	102 mm
Slag	130 mm
Kompresjon	:1	17,4:1	18:1	17,4:1	17,4:1	18:1	18:1
Turbo	Ja
Ladeluftkjøler	Ja
Kjøling	Vann
Ventiler	2 Innsug - 1 Eksos
Innsug åpner	- før ØD
Innsug stenger	- etter ND
Eksos åpner	- før ØD
Eksos stenger	- etter ND
Klaring innsug	mm - kald	0,40 mm
Klaring eksos	mm - kald	0,60 mm
Tenningsrekkefølge	1 - 5 - 3 - 6 - 2 - 4
Dieselpumpe							A 028 074 69 02
Dysespiss
Dieselfilter	A 000 090 15 51						A 000 090 15 51
Oljefilter							A 000 180 17 09
Stempelhastighet	m/s
Stempelprodusent
Startmotor
Produksjonssted
Produksjonstall

OM 906.XXX

OM 906	kW	HK	RPM
.900	205	279
.901	170	231
.903	205	279
.910
.911
.912
.913
.914
.915
.916
.917	170	231
.918	180	245
.919	180	245
.920	170	231

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The new six-cylinder diesel engine OM 906 LA from Daimler-Benz

(From a article in MTZ

With the introduction of the new OM 906 LA six-cylinder in-line engine, Daimler-Benz completes the 900 engine series (BR 900), whose four-cylinder variant, the OM 904 LA, has been on the market since 1996. These engines are designed for both light-duty and heavy-duty commercial vehicles. With a displacement of 6.4 liters, a maximum rated output of 205 kW at 2,300 rpm, and maximum torque of 1,100 Nm at 1,300 rpm, the new engine enters a power range previously covered by engines with significantly larger displacement. This article introduces the new six-cylinder engine.

Introduction

The introduction of the new six-cylinder OM 906 LA diesel engine completes the renewal of the engine product range for commercial vehicles, following the introduction of the four-cylinder OM 904 LA and the 500 series (BR 500) engines in 1996. The design of the OM 906 LA took into account the diverse applications of both Daimler-Benz's global vehicle concepts and those of other automobile manufacturers, each with its own unique requirements. With its current power range of 170 to 205 kW, particularly for on-road use, the OM 906 LA enters a performance segment previously covered by significantly larger displacement engines, such as the 11-liter OM 441 LA. This was addressed through the use of modern technologies and systems, as well as specific testing to ensure a B10 service life of 600,000 km in heavy-duty long-haul applications. This article discusses the design, testing, and, in particular, the comparison with the larger engines previously used in this power segment.

Product concept

The new OM 906 LA six-cylinder engine builds on the basic concept and features of the OM 904 LA four-cylinder engine, introduced in 1996. Both engines were planned as a single engine series from the outset. The design considerations for a new engine series in the power segment between the 600 Series, which was further developed from passenger car diesel engines for commercial vehicle use, and the new V-engines of the 500 Series introduced with the Actros, were essentially based on the following basic requirements:

– Low life cycle costs

– Compliance with global emissions standards

– Heavy-duty characteristics in terms of service life, fuel consumption, and maintenance intervals

– Suitable for application in all vehicles used worldwide by Daimler-Benz and other automobile and equipment manufacturers

– Suitable for use as a horizontal engine in city buses

– High engine braking performance

– Low noise emissions.

Another key criterion in the design of the new engine series was that four-cylinder engines had to be used in the power segment up to 150 kW, especially for distribution transport, due to their short overall length and the associated design advantages for the vehicle (low entry, level cab floor, and thus free access).

With a stroke/bore ratio of 1.27, a mean effective pressure of approximately 17 bar at rated speed, and approximately 22 bar at maximum torque, the technical data shown in Figure 2 resulted. The six-cylinder OM 906 LA engine, in particular, with its maximum output of 205 kW, covers a power segment previously achieved by the large 400 series engines with displacements of 11 l and 12 l. Therefore, a guaranteed B10 service life of 600,000 km was a key focus of testing for the OM 906 LA. The choice of injection system had a significant influence on the engine design. The plug-in pump concept still represents the best solution today, even compared to the common rail systems currently under development, for displacements >1 l per cylinder and the exhaust gas test cycles applicable to commercial vehicles, and it still has sufficient potential for further development in the foreseeable future. The key features of the BR 900 engines have already been described in detail in previous publications [1, 2, 3, 4, 5, 6]. The following section discusses the further development measures following the series launch of the OM 904 LA four-cylinder engine.

Injection system with leak-free single-spring nozzle holder

The OM 904 LA was introduced with the dual-spring nozzle holder concept, particularly due to its noise advantages during idle operation. Since then, the injection system has been further developed so that the required idle noise levels can also be achieved with a single-spring nozzle holder combination without leak-through fuel return ("leak-free"). By eliminating the leak-through fuel return, it has become possible to reduce the nozzle opening pressure – and thus the idle noise – of the single-spring nozzle holder to the low level of the first stage of the dual-spring nozzle holder.

The hydraulic pressure built up during the injection process in the closed spring chamber of the leak-free nozzle holder increases the closing force on the nozzle needle, thus ensuring blowback-free operation of the injection system despite the low opening pressure – set via the compression spring.

To reduce the number of variants, a uniform injection nozzle is used for all engine variants of the 900 series. The resulting uniform injection hole cross-section results in maximum injection pressures of 1,800 bar in the most powerful variant of the OM 906 LA. The same nozzle holder was used for this application as in the 500 series, adapted to the increased stress by selecting a higher-quality material and careful machining to avoid notch effects.

Electronics and Diagnostic Concept

The engines are installed in automobiles and work equipment that have different electronic systems. The overall function of the electronics is therefore divided into two parts: an engine-side control unit and a vehicle-side control unit. The control unit mounted on the engine, which is identical to the 500 Series, is subject to high demands regarding vibration resistance and temperature load. When installed in the Atego, for example, this unit is connected to a vehicle-side control unit (FR) via a data bus. For general applications (Figure 3), the engine control unit is supplemented by an adaptation module (ADM), which covers some of the FR functions. Additional components that meet application-specific requirements can also be connected via a system bus.

For engine diagnostics, the onboard diagnostic system in the vehicle is initially available. A significantly more powerful system, Star Diagnostics, is used worldwide for service. For customers who do not have access to Star Diagnostics, a more cost-effective device with comprehensive diagnostic quality for this application is being developed.

With these diagnostic systems, the rapid and targeted detection of faults in electronically controlled engines during service is significantly easier than with conventional engines with conventional injection systems, which have become very complex due to emissions regulations.

Use of Plastic Components

The main incentive for using plastic components lies, on the one hand, in the weight savings and, on the other hand, in the lower noise emissions with appropriate design. Another advantage is the improved sealing function, since, for tooling reasons, plastics require significantly higher sealing elements with significantly greater working capacity than aluminum die-cast parts, Figure 4. Thermoplastics with varying glass fiber content are used for the cylinder head cover, the charge air housing, and the cover on the injection pump side. The lower thermal conductivity and thus lower heating of the cooled charge air is an additional advantage for the charge air housing compared to an aluminum housing.

A duromer with 30% glass fiber content is used for the oil pan. The 25 mm long glass fibers make the component more resistant to stone chips than an aluminum pan. In the event of serious damage, the oil pan is not completely punctured, but rather a leaky, yet still coherent structure remains, from which the oil only slowly escapes. This gives the driver significantly more time to prevent consequential engine damage.

By using these plastic parts, the overall noise level at a distance of 1 m was reduced by 1.3 dB(A), Figure 5. With the widespread use of large plastic components, the new 900 Series sets future standards in the commercial vehicle engine sector.

Engine Braking System

The six-cylinder engines of the 900 series are equipped with the constant-throttle engine braking system, similar to the four-cylinder engines. The system consists of an exhaust flap – similar to conventional engine brakes – and a constant-throttle valve located in the cylinder head in addition to the gas exchange valves [6].

Due to the gas-dynamic processes in the exhaust tract of the six-cylinder engine, the specific engine braking power increased by approximately 35% compared to the OM 904 LA, so that a brake mean effective pressure of 11 bar and a braking power of 160 kW are achieved at the permissible engine braking speed of 2,700 rpm. The higher brake mean effective pressure of the OM 906 LA also requires greater actuation forces for the constant-throttle valves compared to the OM 904 LA, especially during opening and closing. In order to reliably prevent uncontrolled slamming of the valves caused by gas forces – associated with high landing speeds and high wear – the six-cylinder engines are equipped with hydraulic control of the constant throttle valves instead of the pneumatic control of the four-cylinder engines.

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