BMW M51
| Company type | Engine |
|---|---|
| Industry | Automotive |
| Predecessor | BMW M21 |
| Founded | 1991 |
| Defunct | 2000 |
| Successor | BMW M57 |
| Headquarters | Steyr , Austria |
| Products | 2.5 L straight-six diesel engine |
The BMW M51 is a 2.5-liter straight-six diesel powerplant manufactured at BMW's Steyr facility between 1991 and 2000. This engine replaced the BMW M21 and was later succeeded by the BMW M57.
Description
The M51 is characterized by a water-cooled, turbocharged inline six-cylinder layout, utilizing indirect fuel injection controlled by a Bosch VP37 mechanical pump. It has a displacement of 2,497 cc and operates with a notably high compression ratio of 22.0:1. Certain versions are equipped with an intercooler, identified by the tds suffix. The construction includes a cast iron engine block paired with an aluminum cylinder head, featuring a single overhead camshaft and two valves per cylinder. Enhancements over its predecessor include the incorporation of tappets and hydraulic valve lash adjustment to boost operational efficiency. Initial models and all E36 chassis variants employed Bosch DDE 2.1 engine management systems, which were later updated to DDE 2.2 to improve torque output at lower engine speeds.
| Variant | Output | Torque | Production Years |
|---|---|---|---|
| M51D25 UL | 115 hp (85 kW) at 4800 rpm | 222 newton-metres (164 lbf⋅ft) at 1900 rpm | 1991–1997 |
| M51D25 OL | 105 kW (141 hp) at 4800 rpm | 260 newton-metres (190 lbf⋅ft) at 2200 rpm | 1991–1996 |
| Opel X25DT[lower-alpha 1] | 130 hp (96 kW) at 4800 rpm | 250 newton-metres (180 lbf⋅ft) at 1400 rpm | 1994–2001 |
| M51D25TÜ UL | 115 hp (85 kW) at 4800 rpm | 230 newton-metres (170 lbf⋅ft) at 1900 rpm | 1996–1998 |
| M51D25TÜ OL | 105 kW (141 hp) at 4800 rpm | 280 newton-metres (210 lbf⋅ft) at 2200 rpm | 1996–2000 |
| M51D25M1[lower-alpha 2] | 100 kW (130 hp) at 4400 rpm | 270 newton-metres (200 lbf⋅ft) at 2300 rpm | 1995-2001 |
This engine was utilized in the following vehicles:
- BMW E36 3-Series (models 325td/325tds)
- BMW E34 and E39 5-Series (525td/525tds variants)
- BMW E38 7-Series (725tds)
- Land Rover Range Rover (2.5 D/DSE editions)
- Opel Omega
- A single unit in the UMM Alter II
See also
References
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