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BMW M50

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BMW M50 engine
Overview
ManufacturerBMW
Production1991–1996
Body and chassis
ClassStraight-6
Chronology
PredecessorBMW M20
SuccessorBMW M52

The BMW M50 is an I6 piston engine. It was introduced in 1990 to replace the BMW M20 in the new 3-series and was replaced by the BMW M52 in 1995. Displacement ranges from 2.0 L to 3.2 L. It is a DOHC 24-valve engine. A Technical Update or M50TU version from 1992 introduced VANOS variable valve timing.

The M50 was not related to the M20 though it used the same 91 mm cylinder spacing, bore, and stroke at 2.0 L and 2.5 L. Contrary to its successor, the BMW M52, the M50 has a gray iron engine block, which contributes to its long life expectancy and makes it immune to the corrosive properties of alternative fuels, like E85 ethanol. The rest of the engine is composed of an interesting material mix: the head gasket is made of aluminum alloy, the exhaust manifold consists of cast iron, and the intake manifold was made of plastics in a once revolutionary production process, which was first employed on a grand scale in the manufacture of the BMW M50 engine.

Models
Engine Displacement Power Torque Redline Bore Stroke Year
M50B20 2.0 L (1991 cc/121 in³) 110 kW (150 hp) @ 6000 190 N·m (140 ft·lbf) @ 4700 6750 80mm 66mm 1991
M50TUB20 110 kW (150 hp) @ 5900 190 N·m (140 ft·lbf) @ 4200 6750 80mm 66mm 1993
M50B24 2.4 L 138 kW (188 hp) @ 5900 235 N·m (177 ft·lbf) @ 4700 6550 84mm 72mm 1991
M50B25 2.5 L (2494 cc/152 in³) 141 kW (192 hp) @ 6000 245 N·m (181 ft·lbf) @ 4700 6500 84mm 75mm 1991
M50TUB25 141 kW (192 hp) @ 5900 250 N·m (184 ft·lbf) @ 4200 6500 84mm 75mm 1993
S50B30 3.0 L (2990 cc/182 in³) 210 kW (286 hp) @ 7000 320 N·m (235 ft·lbf) @ 3600 7280 86mm 85.8mm 1992
S50B32 3.2 L (3201 cc/195 in³) 236 kW (321 hp) @ 7400 350 N·m (257 ft·lbf) @ 3250 7600 86.4mm 91mm 1995

M50B20

The 2.0 L (1991 cc) M50B20 was introduced with the 1991 520i. It has an 80 mm bore and 66 mm stroke and produces 150 hp (110 kW). From the '93 model year onwards, the engine received a 'technical update' which included the addition of VANOS (VAriable NOckenwellen Steuerung), BMW's variable valve timing system, on the intake cam. The engine thereafter became known as the M50TUB20.

Applications:

M50B24

This is a 2.4 L engine based on the 2.5 L M50B25, with a reduced stroke. This engine is only fitted to CKD kits assembled in Thailand. Power output is 188 hp (140 kW) and torque is 134 ft·lbf (235 Nm).

Applications:

M50B25

The 2.5 L (2494 cc) M50B25 was introduced with the 1991 525i/525ix . It has an 84 mm bore and 75 mm stroke and produces 192 PS (141 kW; 189 hp) @5900 rpm and 245 N·m (181 lb·ft) @4700 rpm.

Applications:

M50TUB20

The M50TUB20 is a technologically upgraded (TU) version of the BMW M50B20, introduced in 1993. The most notable change present is the inclusion of BMW's VANOS variable cam timing system on the intake cam. Power output remains identical; however, there is a slight increase in torque at lower and medium rpms.

Applications:

M50TUB25

The M50TUB25 is a technologically upgraded (TU) version of the BMW M50B25, introduced in 1993. The most notable change present is the inclusion of BMW's VANOS variable cam timing system on the intake cam. Power output remains identical; however, there is a slight increase in torque at lower and medium rpms 184 vs 181.

Applications:

S50B30

The S50B30 was a special sports-oriented 3.0 L version, which powered the RoW spec E36 M3. Power is 286 hp (210 kW). The S50B30 has a bore of 86 mm and a stroke of 85.8 mm, with a total displacement of 2990 cc. The engine has a maximum permissible speed of 7280 rpm +/-80, and a permissible constant speed of 7000 rpm. It used an Individual Throttle Body intake system with separate butterflies adjacent to each of the 6 inlet ports, an oversized MAF, and a tubular exhaust manifold. The cylinder head was unique and the VANOS system was more advanced than the one used on normal M50s. In USA and Canada, M3 were powered with different engine, lower speced S52B30 based on BMW M52.

Applications:

S50B32

The S50B32 was an evolution version of the S50B30. Power of the 3.2 L version is 317 hp (236 kW). Improvements over the previous 3.0l version include Dual Vanos operating on the exhaust camshaft as well as the inlet camshaft, increased compression ratio to 11.3:1, reduced valve stem thickness (and weight), and higher redline. This engine has a bore of 86.4 mm (3.4 in) and a stroke of 91.0 mm (3.6 in) giving a displacement of 3201 cc. It has a maximum permissible speed of 7600 +/-50 rpm, and a permissible constant speed of 7400 rpm. Power output was rated at 321 PS (236 kW; 317 hp) at 7400 rpm, with a torque rating of 258 lb⋅ft (350 N⋅m) at 3275 rpm.

Applications:

  • 1996-1999 E36 M3 (except for the U.S.)
  • 1997-2000 M Roadster (except for the U.S.)
  • 1998-2000 M Coupe (except for the U.S.)
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