Mercedes Benz
OM 651
Manufacturer:	Daimler AG
Production period:	since 2008
Style:	Four-cylinder in-line engine
Engines:	1.8 liters (1796 cc)  2.1 liters (2143 cc)
Previous model:	OM 646 (in-line four-cylinder)  OM 642 (V six-cylinder)
Successor:	OM 654

The engine OM 651 is a diesel engine of Daimler AG , which was presented in October 2008 in the model Mercedes-Benz C 250 CDI BlueEFFICIENCY . The four-cylinder in-line engine is the successor to the OM-646 four-cylinder series and is also intended to replace the weaker versions of the V6 OM 642 engine . The OM 651 is not a revised version of the OM 646, but was completely redeveloped.

The engine is pre-assembled at the Stuttgart plant , completed by MDC Power in Kölleda (Thuringia). The crankcase is supplied by the iron foundries Fritz Winter and Halberg .

Technology 

The engine has a crankcase made of gray cast iron , a light metal - the cylinder head and the cylinder four V-shaped at an angle of 6 ° overhead valves ( four valves per cylinder ), two overhead camshafts and roller cam, which on resting lash compensation elements are mounted.

The drive of the camshafts sits at the rear end of the engine (output side) to keep the height at the front end as small as possible. This allows for a longitudinally installed engine a flat and rearward rising hood in favor of aerodynamics and pedestrian protection. In order to reduce the length of the engine, the drive is in two stages : first through gears , as they need less space between the engine and transmission, and in the second stage via a single roller chain . The gears also drive the high-pressure fuel pump and two needle-bearing balancer shafts ( Lanchester compensation ).

The displacement is 1796 cc or 2143 cc with a bore of 83 mm and a stroke of 83 or 99 mm, with a cylinder spacing of 94 mm. In the 2.1-liter version (with a connecting rod length of 143.55 mm), the engine has a much longer stroke than its predecessor, which is favorable in terms of higher peak pressure. The compression is 16.2: 1 slightly lower than its predecessor.

The more powerful versions 220 CDI BlueEFFICIENCY and 250 CDI BlueEFFICIENCY two provide turbocharger from BorgWarnerin two-stage arrangement for better cylinder filling. Both turbines and compressors are connected in series: the exhaust gas flows first through the high-pressure turbine, which drives the high-pressure compressor, and then through the low-pressure turbine. The intake air in turn is first passed through the low pressure and then the high pressure compressor. The boost pressure is regulated by an adjustable turbine bypass (similar to a wastegate), which directs the exhaust gas, bypassing the high-pressure turbine, directly to the low-pressure turbine. At high engine speed, the charge air is passed around the high-pressure compressor, so as not to overload the high-pressure supercharger. The boost pressure for the 150 kW version is just under 3 bar (absolute).

The weaker units up to 105 kW have a single turbocharger with variable turbine vanes (VTG loaders) from IHI . All versions have a charge air cooler (Intercooler).

There is a cooled exhaust gas recirculation (EGR) with pre-cooler and main cooler. Depending on the operating point of the engine, the main radiator is bypassed by an exhaust gas recirculation (EGR) valve manufactured by Handtmann to control the temperature of the recirculated exhaust gases.

Injection 

The common-rail injection works with a fuel pressure up to 2000 bar. The weaker engine variants have solenoid-operated, the stronger ones, however, piezo injectors in which the nozzle needle is operated directly, so that up to five individual injections are possible per combustion process. The closed design of these injectors also eliminates the leakage line.

The high-pressure fuel pump is throttled on the suction side to adjust the flow rate as needed. This reduces the heating of the diesel engine so that it does not require a radiator and also reduces the pump drive power.

Cooling and lubrication 

The engine has a demand-controlled water pump . The controller can shut off the flow of coolant through a pneumatically controlled gate to firstly consume less power to drive the pump, and secondly, to heat the combustion chambers faster when the engine is cold. The setpoint temperature of the coolant is normally 100 ° C, but is reduced at high load and also up to 80 ° C depending on the driver's behavior.

The oil pump is a vane pump with pressure-dependent delivery rate. It regulates the pressure in the main oil passage after the oil filter to reduce the drive power of the pump at low filter load. The piston cooling via oil spray nozzles is switched on or off depending on the map. On the one hand, this reduces the drive power of the oil pump when no piston cooling is necessary at low load. On the other hand, the hydrocarbon emission is reduced when the engine is cold due to the higher piston temperature.

Versions 

The OM 651 is currently available in car models in ten different performance levels:

OM 651 DE 18 LA red.

OM 651 DE 18 LA 

OM 651 DE 22 LA red. 

OM 651 DE 22 LA 

According to Mercedes-Benz, the engine has not yet reached its performance limit. At least 162 kW are still possible. The torque of the engine could be increased so far that it could be quite a replacement for the current OM 642 in the 320 CDI with 165 kW and 540 Nm of torque in terms of its performance data.

All versions comply with the Euro 5 emission standard and the basic design of the engine already meets the Euro 6 emissions standard that the ML 250 BlueTEC will meet from 2011 onwards.

The engine was initially offered in the C-Class class 204 in late summer 2008 in a Frontrunner series called "PrimeEdition" (5000 pieces). Out of use in the following GLK and since May 2009 in the E-Class 212 series / 207 model series . Since 2010, the remaining series have also been equipped with the new machine. This engine is even offered in the S-Class since the end of September 2010 in the highest expansion stage . Since November 2011, he is also incorporated in the B-Class, but here across. The displacement was reduced to 1.8 liters.

Technical problems 

Shortly after the launch of the engine, quality issues became known with the piezo injectors supplied by Delphi . Of these, the two more powerful expansion stages with 125 kW and 150 kW were affected, but the lower-power variants were not, since they have magnetically controlled injectors. The problem usually occurs at a mileage of 50,000 km. In the event of damage, the affected engines only have limited power , as the engines automatically switch to the emergency program to prevent further damage . The vehicle can be so at low speedcontinue. Some customers admitted that Mercedes-Benz was not able to replace all injectors of the defective series in the affected vehicle due to capacity bottlenecks at the supplier's , but only individual failed injectors. As a result, customers had to visit a garage up to four times to replace all four injectors. In the further course, however, all injectors were replaced at once. Altogether, according to various sources, between 2,800 and 50,000 vehicles were affected, elsewhere, there is talk of up to 300,000 vehicles. Due to the high failure rate only a few engines with Delphi piezo injectors are built. The performance of the Delphi magnetic injectors has been increased to 145 kW, so that also the 220 CDI and 250 CDI models equipped with it. In addition, occasionally Bosch magnet injectors in the four-wheel and M-class variants are used.

Another problem is the water pump. This is leaking in many cases.

The engine is equipped with a simplex timing chain (instead of duplex chain). Increased wear of the timing chain and / or the chain tensioner are recorded at higher mileage. The replacement of the timing chain is quite complex, since the timing chain is installed on the rear side of the transmission and thus, in contrast to front timing drives, the expansion of the engine and transmission is required to repair the timing drive.

At the end of November 2014, problems with the chain tensioner became known again. After that failure, the chain tensioner and possibly leak engine oil. All vehicles produced between February and November 2014 have been recalled by the manufacturer.

Exhaust emission.

The diesel engine OM 651 is according to media reports  is based on the suspicion that the engine contains an inadmissible defeat device, whereby the exhaust levels on the test bench are better than in actual use. This concerns more than one million vehicles of different vehicle classes, which were sold in the years 2008 to 2016 in Europe and the USA with an inadmissibly high pollutant emission. 

Mercedes Benz
OM 646, OM 647, OM 648
Manufacturer:	Mercedes Benz
Production period:	2002-2010
Style:	Inline four-cylinder OM 646 Inline five-cylinder OM 647 in-  line six-cylinder OM 648
Engines:	2.2 liters (2148 cc)  2.7 liters (2685 cc)  3.2 liters (3222 cc)
Previous model:	OM 611 (4-cylinder)  OM 612 (5-cylinder)  OM 613 (6-cylinder)
Successor:	OM 651 (4-cylinder)  OM 642 (6-cylinder)

The OM 646 by Mercedes-Benz is a four cylinder - diesel engine with common-rail direct injection . Vehicles with this engine type carry mostly "200 CDI" and "220 CDI" in the sales name. The engine type represents a further development of the OM 611 .

The article also covers the OM 647 ("270 CDI") five cylinder engines and OM 648 ("280 CDI", "320 CDI") six-cylinder engines, also in- line , which are technically closely related to the OM 646.

These engines were mainly installed in the years 2002 to 2010 in several series, including the C-Class and the E-Class , as a six-cylinder in the S-Class and in vans such as the Sprinter .

Technology 

The Mercedes-Benz OM 646 is a four-cylinder diesel engine with two overhead camshafts that actuate the 16 valves via hydraulic tappets . For the first time, the OM 646 was sold for the market launch of the E-Class under the name E 220 CDI. In a direct comparison with its predecessor, consumption has been further reduced and the engine performance can be increased. This is due to modifications to over 80 components . For continuous compliance with the exhaust emission values, an on-board diagnosis was madeInstalled system, which monitors all exhaust-related components in the engine and exhaust system. To improve the smoothness, the more powerful models (220 CDI) were equipped with two Lanchester balancer shafts. They rotate in opposite directions at twice the crankshaft speed and eliminate any mass forces caused by the piston movement.

The mechanical fuel pump has been replaced by an electric version, which performs its service in the tank. In order to ensure sufficient interior heating, one was PTC - heater installed. Compared to its predecessor, not the coolant is heated here, but only the air flowing into the interior. Starting in 2003, a soot particulate filter in conjunction with the Euro 4 emission standard was initially offered as an option, and later as standard .

For the first time, this type of engine uses third-generation common rail direct injection . System supplier is Bosch . The fuel distribution takes place as before via a common fuel rail (common rail)in which the fuel pressure is kept continuously high by a high pressure pump. The system pressure was increased compared to the previous engine. Through the line, the fuel enters the solenoid valve-controlled injection nozzles, from which it is injected at a pressure of up to 1600 bar through seven holes in the combustion chamber. The new injectors distribute the fuel even finer in the combustion chamber. New from this engine type are two-fold pilot injections, by means of which a small amount of fuel is introduced before the actual combustion in the cylinder and burned there. As a result, the combustion chamber heats more effectively, thus lowering the temperature and pressure increase in the main combustion. This ensures an improved running smoothness.

The engine is supercharged by a turbocharger with variable turbine geometry , as in the OMI 611 of the CDI Series II . It has adjustable vanes on the exhaust side , which ensure faster buildup of boost pressure. This improves the cylinder filling and thus the torque. The so-called turbo lag is thereby reduced. The boost pressure controlis achieved by adjusting the vanes. This is electronically controlled unlike the predecessor model. Exceptions are the engines in the Mercedes Sprinter. These are realized in the somewhat higher-powered vehicles via a high and a low-pressure supercharger (two-stage supercharging) by means of negative pressure. It uses a wastegate and a wastegate, which significantly improves engine efficiency and responsiveness.

To cool down the compressed hot charge air and bring more oxygen into the combustion chamber, a charge air cooler is installed.

The intake section of the OM 646 is equipped with the EKAS (intake channel deactivation) , which is already known from the OM 611 . Of the two intake ports per cylinder, one channel, the tangential, can be switched off at low speeds. The sucked air flows now completely through the specially shaped second channel, the swirl duct. The resulting swirl leads to a better mixture formation, whereby a better combustion is achieved. The EKAS is controlled electronically and works steplessly. Unlike the predecessor, the pneumatically controlled exhaust gas recirculation valve was replaced by an electronically controlled version. It reduces the excess air and lowers the temperature by exhaust gasesthe sucked fresh air are supplied. This reduces nitrogen oxide emissions and combustion noise. To regulate the exhaust gas recirculation, a hot-film air mass meter is installed, which allows an accurate measurement of the intake air mass.

OM 646 EVO

In 2006, the OM 646 EVO was presented as part of the facelift for the E-Class . It is an advanced version of the OM 646, in which over 90 components have been modified. The compression ratio has been reduced from 18.0: 1 to 17.5: 1 by installing higher pistons and shorter connecting rods. In addition, a new turbocharger with modified charge air cooling was installed. A structure-borne sound sensor in the injection system allows a more appropriate metering of the fuel. The cylinder head has been redesigned to achieve even more effective engine cooling. The air duct was also redesigned. This reduced pressure loss and noise emissions. For improved engine start and cold running behavior were the glow plugsmade of ceramic instead of metal. They allow higher annealing temperatures. The balance shafts previously known from the larger variants were introduced in all OM 646 EVO engines.

Five-cylinder OM 647 and six-cylinder OM 648

The modifications of the OM 611 to the OM 646, with the exception of the balance shafts, were also adopted for the OM 612 (five-cylinder) and OM 613 (six-cylinder) series. The result was the OM 647 and OM 648 series, which differ structurally from the OM 646 by the number of cylinders; Bore and stroke are the same for all engines of this engine family.  The modifications of the OM 646 EVO (four-cylinder) were the series OM 647 (five-cylinder), and OM 648 (six-cylinder) is no longer beneficial, since these by weaker variants of the following V6 engine OM 642 were replaced.

Data 

Mercedes Benz
OM 642
Manufacturer:	Mercedes Benz
Production period:	since 2005
How it works:	diesel
Style:	Six-cylinder V-engine
Engines:	3.0 liters (2987 cc)
Previous model:	OM 648
Successor:	OM 656

The built in Berlin the OM 642 -Motor is a diesel engine type with six cylinders in V-arrangement , common-rail direct injection and turbocharger , developed and produced by Daimler for use primarily in the Mercedes-Benz -cars. The engine has a non-standard cylinder bank angle of 72 degrees for V6 engines.

These engines are installed in several performance levels in passenger cars of all series, SUV , vans from Mercedes since March 2005 and stand (as of 2018) in the current production program of Mercedes -Benz.

The abbreviation "OM" stands for "oil engine" (engine, which is operated with light oil / diesel) and designates since the beginning (1920s) until today the diesel engines of the Daimler AG .

History 

In March 2005, the OM 642 was first used in the Mercedes model C 320 CDI of the C-Class 203 series . As of July 2005, the new V-engines were also installed in the E 280 CDI and E 320 CDI in the E-Class 211 series . The engine is a more modern design compared to the previous five- and six-cylinder OM 647 and OM 648 series engines .

The newer strong CDI engines are in the types E 280 CDI (eponymous to the predecessor with the throttled OM 648) and E 320 CDI (eponymous to its predecessor with OM 648) now V6 cylinder. Their advantages are higher torque , higher power , better exhaust emissions and lower production costs . In addition, thanks to the shorter overall length, they now also fit in the C-Class and the ML.

With the appearance of the new OM 651 , the 280 CDI was replaced in the medium term by the new 150 kW four-cylinder engine, which not only has a higher output, but also lower fuel consumption. At the beginning of 2010, however, a performance-throttled 300 CDI was introduced , analogous to the 250 CDI in the E-Class . With 150 kW and 500 Nm, it has the same performance level as the four-cylinder engine ( OM 651 ).

In autumn 2010, the S-Class , the R-Class and the current E-models received an uprated version of the diesel engine called the OM 642 LS. It provides 170 to 195 kW and 540 to 620 Nm. The new 300 CDI now reaches the power level of the previous 350 CDI (without LS), the previous 300 CDI with 150 kW omitted.

Prototypes 

In 2005 there was a test with a turbocharged OM 642 in the showcar SLK 320 CDI Triturbo . There he made 210 kW and 630 Nm. The V6 engines came in the course of their development in areas of the previous V8 diesel OM 629 before. There are within the scope of the EU legislation mandatory for manufacturers CO ₂ savings a trend towards " downsizing to be replaced by highly charged, lighter and more fuel-efficient engines with smaller displacements and smaller numbers of cylinders," sucker engines.

The motors are produced in a consistently used modular system. All engines are manufactured at the Berlin-Marienfelde production facility on an assembly line of ThyssenKrupp Krause GmbH. The eight-cylinder CDI OM 629 also builds on the same basis .

Use and performance differentiation of the OM 642 

As with the four-cylinder engines in the C- and E-Class (180 CDI / 200 CDI / 220 CDI / 250 CDI), all model designations (280, 300, 320 and 350) refer to the V6 with an identical displacement of 3.0 liters , Except for the model E 300 CDI here the engine designation does not match the actual displacement. The most powerful version of the engine currently produces 195 kW (265 hp).

The same displacement versions with different capacities Type OM 642 DE 30 LA red. with 140  kW and type OM 642 DE 30 LA with 165 kW / 173 kW differ only by their engine peripherals, by turbocharger , common-rail injection system and the engine controls. There are no component differences in the engine between E 280 CDI and E 320 CDI .

OM 642 DE 30 LA red. 

OM 642 DE 30 LA 

OM 642 LS DE 30 LA 

In addition, the engine has been used with slight modifications in some Chrysler vehicles, e.g. In the Chrysler 300C 3.0 CRD or in the Jeep Grand Cherokee .

Technology

The OM 640 has one common-rail injection and four valves per cylinder. All variants are equipped with engine charging and intercooling. As usual with Mercedes, the overhead camshafts are driven by two timing chains .

The motor is inclined forwards by approx. 60 ° and is installed transversely behind the driven front axle on vehicles with sandwich floor . Power is transmitted via a manual gearbox with five (160 CDI) or six gears (180 CDI and 200 CDI) or via the continuously variable Autotronic . The engine and transmission could only be used in these vehicles due to their unusual installation position.

OM 640 

OM 639 

On the basis of the OM 640, a version capped by a cylinder was used in the 2004 Smart Forfour and Mitsubishi Colt . Also, the OM 639 has timing chains and a common-rail injection, with the exception of the missing fourth cylinder, data such as bore and stroke are identical. However, the installation position is typical for front-wheel drive: engine standing transversely in front of the front axle. It was offered in two performance levels: