The OM651 is a family of
inline-four cylinder automobile
diesel engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...
s introduced by
Mercedes-Benz
Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
in 2008.
Design
The main goal was to create a common engine design that maximized the parts commonality between the engines manufactured by parent company, Daimler.
One requirement of the design was the ability of the engine to be mounted both
longitudinally and
transversely. Improved
fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, wh ...
and compliance with
Euro 5
The European emission standards are vehicle emission standards for pollution from the use of new land surface vehicles sold in the European Union and EEA member states and the UK, and ships in EU waters. The standards are defined in a seri ...
emission standards
Emission standards are the legal requirements governing air pollutants released into the atmosphere. Emission standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources over ...
were also design objectives, by 2010 being updated to the
Euro 6
The European emission standards are vehicle emission standards for pollution from the use of new land surface vehicles sold in the European Union and EEA member states and the UK, and ships in EU waters. The standards are defined in a seri ...
standard; four piezo-electric injectors fed with very high pressure fuel from a common rail inject fuel directly into the
combustion chamber
A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process.
Interna ...
s to improve combustion compared to previous Mercedes Diesel engines and recirculated
exhaust gas
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...
reduces the oxygen in the cylinders to "starve" any reactions that would produce NO(x).
There are 6 variants in all. Of these 4 variants of the engine have the same swept volume, tuned to different power outputs
(badged x180 on rear wheel drive models (badged x200 on rear wheel drive models) (badged x220) to (badged x250). The and versions employ a 2 stage (bi-turbo) charging setup with a small, high pressure turbo providing quick boost at low RPM fed by a large, lower pressure turbo providing increased performance at higher RPM, then at highest rpm ranges and loads, using both simultaneously. The lower output version has only a single turbocharger.
There are also 2 shorter stroke "square" variants of this engine with 1.8 litre displacement (badged A/B180) (badged A/B200 and used only in smaller front wheel drive models like the A-Bclass). These two variants differ only in electronic tune, and have a single turbocharger.
See also
*
List of Mercedes-Benz engines
Mercedes-Benz has produced a range of petrol, diesel, and natural gas engines. This is a list of all internal combustion engine models manufactured.
Petrol engines Straight-three
* M160, 0.6 – 0.7 L (1998–2007)
* M281, 0.9 - 1.0 L (20 ...
*
List of engines used in Chrysler products
References
OM651
Diesel engines by model
Straight-four engines
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