BMW M50 Straight-6 Engine
From 1990 to 1996
The BMW M50 is a straight-6 DOHC piston engine was produced from 1990-1996. It was released in the E34 520i and 525i, to replace the M20 engine. It began to be phased out following the introduction of the M52 engine in 1994.
Compared with its M20 predecessor, the M50 features DOHC, 4 valves per cylinder, coil-on-plug ignition, a knock sensor and a lightweight plastic intake manifold. As per the M20, the M50 uses an iron block with an alloy head.
In September 1992, the M50 was upgraded to the M50TU ("technical update"), which added variable valve timing to the intake camshaft (called single VANOS by BMW).
The E36 M3 was powered by the S50 engine series, which is a high output version of the M50.
|M50B20||1,991 cc (121 cu in)||110 kW (148 bhp) @ 6000||190 N·m (140 lb·ft) @ 4700||6500||80 mm (3.1 in)||66 mm (2.6 in)||10.5||1990|
|M50B20TU||110 kW (148 bhp) @ 5900||190 N·m (140 lb·ft) @ 4200||6500||80 mm (3.1 in)||66 mm (2.6 in)||11.0||1992|
|M50B24||2,394 cc (146 cu in)||115 kW (154 bhp) @ 5900||235 N·m (173 lb·ft) @ 4700||6550||84 mm (3.3 in)||72 mm (2.8 in)||1991|
|M50B25||2,494 cc (152 cu in)||141 kW (189 bhp) @ 5900||245 N·m (181 lb·ft) @ 4700||6500||84 mm (3.3 in)||75 mm (3.0 in)||10.0||1990|
|M50B25TU||141 kW (189 bhp) @ 5900||245 N·m (181 lb·ft) @ 4200||6500||84 mm (3.3 in)||75 mm (3.0 in)||10.5||1992|
|S50B30 (Euro-spec)||2,990 cc (182 cu in)||213 kW (286 bhp) @ 7400||350 N·m (258 lb·ft) @ 3250||7600||86 mm (3.4 in)||86 mm (3.4 in)||10.8||1992|
|S50B30(US-spec)||179 kW (240 bhp) @ 6000||305 N·m (225 lb·ft) @ 4250||6500||86 mm (3.4 in)||86 mm (3.4 in)||10.5||1993|
|S50B32(Euro-spec)||3,201 cc (195 cu in)||239 kW (321 bhp) @ 7400||350 N·m (258 lb·ft) @ 3600||7400||86.4 mm (3.4 in)||91 mm (3.6 in)||11.3||1995|
|S52B32(US-spec)||3,201 cc (195 cu in)||179 kW (240 bhp) @ 6000||320 N·m (236 lb·ft) @ 3600||6500||86.4 mm (3.4 in)||91 mm (3.6 in)||10.5||1995|
The 1,991 cc (121 cu in) M50B20 was introduced with the 1990 520i. It has an 80 mm (3.1 in) bore and 66 mm (2.6 in) stroke and produces 110 kW (150 hp). Compression Ratio 10.5:1.
- 1990-1992 E34 520i
- 1991-1992 E36 320i
The M50B20 was updated with single VANOS in 1992. Compression Ratio raised to 11:1. Peak torque became available at 4200 rpm.
- 1992-1994 E36 320i
- 1992-1996 E34 520i
This is a 2.4 L engine used in the Thailand and Oceania markets. It is based on the 2.5 L M50B25 with a reduced stroke.
The 2,494 cc (152 cu in) M50B25 was introduced with the 1990 525i and 525ix. It has an 84 mm (3.3 in) bore and 75 mm (3.0 in) stroke and produces 141 kW (189 hp) at 6000 rpm and 245 N·m (181 lb·ft) at 4700 rpm.
- 1990-1992 E34 525i, 525ix
- 1991-1992 E36 325i, 325is
The M50B25 was updated with single VANOS in 1992. Peak torque became available at 4200 rpm.
- 1993-1995 E36 325i, 325is
- 1992-1996 E34 525i, 525ix
The S50 is the high performance version of the M50 which was used in the M3. Like the M50, it has an iron block and aluminum head with four valves per cylinder.
In the USA, 1994-1995 M3 models are powered by the "S50B30US" (which was replaced by the 3.2 S52 in 1996).
The S50B30 is a 2,990 cc (182 cu in) higher output version of the M50 which powered the E36 M3, except in the USA. Canada had a limited production run of 45 cars with the S50B30 engine.
Engine management is provided by a Bosch Motronic M3.3 ECU with a separate "VNC" Vanos control unit providing fully variable single camshaft adjustment on the intake side. It produces 213.5 kW (286 hp), has a bore of 86 millimetres (3.4 in) and a stroke of 86 millimetres (3.4 in), and a compression ratio of 10.8:1. The limited edition "M3 GT" model from 1995 had different camshafts and a redesigned sump and oil pump, and produced 220 kW (295 hp).
Upgrades over the M50 include:
- Individual throttle plates for each cylinder
- Continuously variable "Vanos" valve timing.
- Lightweight pistons
- Graphite-coated connecting rods
- Larger inlet valves
- Redesigned equal length exhaust manifolds
- 1992-1995 E36 M3 (except for USA)
USA versions of the 1994-1995 E36 M3 are powered by a 3.0L tuned version of the M50 which produces 179 kW (240 hp). This engine was based on the M50B25TU and uses the same compression ratio,but uses a different crankshaft, connecting rods, and pistons. At the 1996 facelift, this engine was replaced by the 3.2 L S52.
- 1994-1995 E36 M3 (USA only)
In 1996, the 3,201 cc (195 cu in) S50B32 replaced the S50B30 (except in Canada and USA, where the M52-based S52 engine was used instead). Engine management is provided by a Siemens MSS50 engine control unit featuring integrated Vanos control for both the intake and exhaust camshafts. The MSS50 ECU also encompassed an advanced knock control system which can monitor each of the s50b32 6 cylinders via 3 knock sensors allowing the engine run a more refined calibration on standard high octane pump gas. The oil sump is a smaller capacity unit first seen on the M3GT and features a dual pick-up system to lower the risk of oil being forced away from a single pick-up point under cornering. This engine produces 239 kW (321 hp). The compression ratio is 11.3:1, the bore is 86.4 mm (3.4 in) and the stroke is 91 mm (3.6 in).
Performance Z3 M coupe
|Top Speed||155 mph|
|0-60 mph||5.2 secs|
|Torque||350 Nm, 258 ft-lb|
|CO2 Emissions||268 g/km|
|Euro Emissions Standard||2|
- 1996-1999 E36 M3 (except Canada and USA)
- 1996-1999 Z3 M coupe and M roadster (except Canada and USA)