Mercedes-Benz OM651 engine
The OM651 is a family of inline-four cylinder automobile diesel engines introduced by Mercedes-Benz in 2008.
| Mercedes-Benz OM651 | |
|---|---|
 | |
| Overview | |
| Manufacturer | Mercedes-Benz |
| Production | 2008–present |
| Layout | |
| Configuration | Inline 4[1] |
| Displacement | 1.8 L (1,796 cc) 2.1 L (2,143 cc) |
| Cylinder bore | 83 mm (3.27 in) |
| Piston stroke | 83 mm (3.27 in) 99 mm (3.9 in) |
| Block material | Cast iron [2] |
| Head material | Aluminium alloy |
| Valvetrain | DOHC |
| Compression ratio | 16.2:1 |
| Combustion | |
| Turbocharger | Single turbo / twin-turbo |
| Fuel system | Common rail |
| Fuel type | Diesel |
| Cooling system | Water cooled |
| Output | |
| Power output | 100–150 kW (134–201 hp) |
| Chronology | |
| Predecessor | Mercedes-Benz OM646 engine |
| Successor | Mercedes-Benz OM654 engine |
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 and compliance with Euro 5 emission standards were also design objectives, by 2010 being updated to the Euro 6 standard; four piezo-electric injectors fed with very high pressure fuel from a common rail inject fuel directly into the combustion chambers to improve combustion compared to previous Mercedes Diesel engines and recirculated exhaust gas reduces the oxygen in the cylinders to "starve" any reactions that would produce NO(x).
There are 5 variants in all. Of these 3 variants of the engine have the same 2.1 L (2,143 cc) swept volume, tuned to different power outputs 136 PS (100 kW) (badged x200 on rear wheel drive models) 170 PS (125 kW) (badged x220) to 204 PS (150 kW) (badged x250). The 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, 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 109 PS (80 kW) (badged x180) 136 PS (100 kW) (badged x200 and used only in smaller front wheel drive models like the A-class). These two variants differ only in electronic tune, and have a single turbocharger.