BMW M50

Infobox Automobile
name=BMW M50 engine
manufacturer=BMW
production=1989–1994
predecessor=BMW M20
successor=BMW M52
class=Straight-6
engine=
similar=Mercedes-Benz M103The BMW M50 is an I6 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 related to the M20 with the same 91 mm cylinder spacing, bore, and stroke at 2.0 L and 2.5 L.

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:
* 1990-1995 E36 320i
* 1989-1995 E34 520i

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 177 ft·lbf (240 Nm).

Applications:
* 1993-1997 E36 3-Series (Thai specification)
* 1993-1997 E34 5-Series (Thai specification)

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).

Applications:
* 1991-1995 E34 525i/525ix
* 1992-1995 E36 325i/325is

M52B28

Updated version of the m50, utilizing a larger 84 mm stroke to reach 2.8 liters. This engine featured a revised intake manifold with narrower runners so as to restrict peak output while maintaining low-end torque. European versions had an all-alloy block while North American variants had a cast iron block. The Z3 sports car was the exception; it used an alloy block in all markets. The ECU was changed from a Bosch Motronic to a Siemens MS41 which incorporated OBD 2 software. These engines featured VANOS variable valve timing on the intake cam.

Applications:
* 1996-2000 [BMW e36 and e46 328i]
* 1996-2000 [BMW e39 528i]
* 1996-2000 [BMW Z3 2.8i]

For 1999 and 2000, there were updates to this engine, which was known as the M52TU.

M50B30US

The M50B30US 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:
* 1995 E36 M3

50B30

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:
* 1992-1995 E36 M3

50B32

The S50B32 was an evolution version of the S50B30. Power of the 3.2 L version is convert|321|hp|abbr=on. 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 M52B32, 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 M52B32 was only convert|240|hp|abbr=on and maximum permissible engine speed was in the 6500 rpm range since it used hydraulic lifters instead of solid ones.

Applications:
* 1996-1999 E36 M3
* 1997-2000 M Roadster
* 1998-2000 M Coupe

54B32

The S54B32 was a redesigned S50B32 engine with marginally more displacement and yielding more power than the previous models, convert|338|hp|abbr=on in Europe and convert|333|hp|abbr=on in US specification, at 7900 rpm. It developed convert|262|ft.lbf|N.m|abbr=on 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 convert|360|hp|abbr=on at 7900 rpm with convert|273|ft.lbf|N.m|abbr=on of torque at 4300 rpm.

Applications:
* 2001-2006 BMW E46 M3
* 2000-2002 BMW Z3 M Roadster
* 2001-2002 BMW Z3 M Coupe
* 2006-current BMW Z4 M Roadster
* 2006-current BMW Z4 M Coupe

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