BMW M50

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BMW M50 engine
Automotive industryBMW
Production1989–1994
PredecessorBMW M20
SuccessorBMW M52
Car classificationStraight-6

The BMW M50 is an Straight-6 Piston engine. It was introduced in March 1989 to replace the BMW M20 and was replaced by the BMW M52 in 1994. 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. When this technology was introduced, it was known as VACC or Variable Camshaft Control.

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.

Models
EngineDisplacementPowerTorqueRedlineYear
M50B202.0 L (1991 cc/121 in³)110 kW (148 hp) @ 5900190 N·m (140 ft·lbf) @ 470067501989
M50B242.4 L110 kW (148 hp) @ 5900
M50B252.5 L (2494 cc/152 in³)141 kW (189 hp) @ 5900245 N·m (181 ft·lbf) @ 470065001989
141 kW (189 hp) @ 5900250 N·m (184 ft·lbf) @ 420065001992
141 kW (189 hp) @ 5900245 N·m (181 ft·lbf) @ 420065001992

Contents

M50B20


The 2.0 L (1991 cc) M50B20 was introduced with the 1989 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' including VACC (Variable camshaft control) and 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 assembled in Thailand. Power output is 188 hp (140 kW) and torque is 177 ft·lbf (240 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 hp (141 kW). Also, it had a very wide range of acceleration : 1st gear - over 60 km/h; 2nd - 120 km/h, 3rd - 170 kmh. It is very much possible, that if it had no rev limiter, it could perform 180 km/h in 3rd.

Applications:

S50B30US

The S50B30US was a 3.0 L version, which powered the US-spec E36 M3. Power was 240 hp (179 kW). Unlike the RoW S50, this engine used a regular M50 intake in lieu of the individual throttle body set up and hydraulic valve lifters in lieu of solid ones. The cylinder head and the VANOS system are also different on the US M50 versus the RoW model; again having more in common with the regular M50 than the Euro S50.

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 ITB intake system with 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.

Applications:

S50B32

The S50B32 was an evolution version of the S50B30. Power of the 3.2 L version is 321 hp (239 kW). This engine has a bore of 86.4 mm and a stroke of 91.0 mm giving a displacement of 3201 cc. It has a maximum permissible speed of 7600 +/-50 rpm, and a permissible constant speed of 7400 rpm.

The US counterpart, the BMW S52B32, shared some of the European versions' internal dimensions but was festooned with the restrictive M52B28 intake manifold and used a cylinder head design more akin to the M52 than to its fire-breathing European cousin. Power for the S52B32 was only 240 hp (180 kW) and maximum permissible engine speed was in the 6500 rpm range since it used hydraulic lifters instead of solid ones.

Applications:

S54B32

The S54B32 was a redesigned S50B32 engine with marginally more displacement and yielding more power than the previous models, 343 hp (256 kW) in Europe and 333 hp (248 kW) in US specification, at 7900 rpm (slightly less for the "Z" models). It developed Convert/ft.lbf of torque at 4900 rpm. The S54 was the final, most powerful evolution of the M50 engine line, incorporating individual throttle bodies, drive-by-wire throttle control, and variable valve timing (VANOS) for both intake and exhaust camshafts.

BMW also produced an even more powerful version of the S54B32, for the limited edition E46 M3 CSL. This engine lacked a conventional mass airflow meter, and BMW installed modified intake and exhaust camshafts, as well as a more efficient air intake system. This version yielded 360 hp (270 kW) at 7900 rpm with Convert/ft.lbf of torque at 4300 rpm.

Applications:

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