Mercedes-Benz OM651 engine

Mercedes-Benz OM651
Overview
Manufacturer	Mercedes-Benz
Production	2008–present
Layout
Configuration	Inline-4 [1]
Displacement	1,796 cc (1.796 L) 2,143 cc (2.143 L)
Cylinder bore	83 mm (3.27 in)
Piston stroke	83 mm (3.27 in) 99 mm (3.9 in)
Cylinder block material	Cast iron [2]
Cylinder head material	Aluminium alloy
Valvetrain	DOHC, chain-driven and gears
Compression ratio	16.2:1
Combustion
Turbocharger	Single turbo / bi-turbo
Fuel system	Common rail
Fuel type	Diesel
Cooling system	Water cooled
Output
Power output	80–150 kW (107–201 hp)
Chronology
Predecessor	Mercedes-Benz OM646 engine
Successor	Mercedes-Benz OM654 engine

The Mercedes-Benz OM651 is a family of inline-four diesel engines introduced by Mercedes-Benz in 2008.

Design

The main goal was to create a common engine design that shared parts across the line.

One design requirement was that the engine could be mounted both longitudinally and transversely.

Improved fuel efficiency and compliance with Euro 5 emission standards were other design objectives, by 2010 updated to the Euro 6 standard. Four piezo-electric injectors fed with high pressure fuel from a common rail inject fuel directly into the combustion chambers to improve combustion compared to previous diesel engines while recirculated exhaust gas reduces the oxygen in the cylinders to "starve" any reactions that would produce NO(x).

Variants

Of the 6 variants, 4 have the same 2.2-litre swept volume, tuned to different power outputs 120 PS (88 kW) (badged x180 on rear-wheel drive models), 136 PS (100 kW) or 143 PS (105 kW) (badged x200 on rear-wheel drive models), 163 PS (120 kW) or 170 PS (125 kW) (badged x220) to 204 PS (150 kW) (badged x250). The 163 PS (120 kW), 170 PS (125 kW) and 204 PS (150 kW) 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, both were active. The lower output versions have a single turbocharger.

Two shorter stroke "square" variants had 1.8-litre displacement 109 PS (80 kW) (badged A/B180) and 136 PS (100 kW) (badged A/B200 and were used in smaller front-wheel drive models like the A-B class). These two variants differ only in electronic tune, and have a single turbocharger.

See also

• List of Mercedes-Benz engines

References

1. Meiners, Jens (22 December 2009). "Mercedes Engine Transplant: Modern Diesel in a 1992 190E 2.6". Car & Driver . Retrieved 2025-07-05.
2. "Mercedes Debuts New Generation of Four-Cyindler Diesel Engines". eMercedesBenz. 11 April 2008. Archived from the original on 2018-11-29. Retrieved 2015-01-13.