BMW M51


The BMW M51 is an inline-6 cylinder Diesel engine produced by the Upper Austrian BMW plant in Steyr from July 1991 through February 2000. Its predecessor is the BMW M21; the successor is the BMW M57.

Description

The M51 is a water-cooled and turbocharged inline six-cylinder diesel engine. It is an indirect injection design with fuel supplied by a Bosch VP37 mechanical injection pump. The displacement is 2,497 cc and the compression ratio is 22.0:1.
Some engine variants have an intercooler in addition to the turbocharger; vehicles so equipped can be identified by the designation tds. The M51 has a cast iron block and aluminum head, one chain driven overhead camshaft, and two valves per cylinder. Compared to the M21 the M51 features tappets and hydraulic valve lash adjustment. The fuel injection in the first engines and all E36 models is controlled by the Bosch DDE 2.1, which was replaced after the first technical revision by DDE 2.2, resulting in greater torque at lower revs. For lubrication SAE 5W-40 oil is used.
VersionPowerTorqueYears
M51D25 UL
at 4800 rpm
at 1900 rpm		1991–1997
M51D25 OL
at 4800 rpm
at 2200 rpm		1991–1996
Opel X25DT
at 4800 rpm
at 1400 rpm		1994–2001
M51D25TÜ UL
at 4800 rpm
at 1900 rpm		1996–1998
M51D25TÜ OL
at 4800 rpm
at 2200 rpm		1996–1998
M51D25TÜ OL
at 4600 rpm
at 2200 rpm		1998–2000
M51D25M1
at 4400 rpm
at 2300 rpm		1995-2001

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