The BMW M50 is a straight-6 DOHC petrol engine which was produced from 1990 to 1996. It was released in the E34 520i and 525i, to replace the M20 engine.
In September 1992, the M50 was upgraded to the M50TÜ (Technische Überarbeitung, "technical revision"). This was BMW's first engine to use variable valve timing. Called single VANOS by BMW, the system adjusted the phasing of the intake camshaft.
The M50 began to be phased out following the introduction of the M52 engine in 1994.
The E36 M3 is powered by the S50 engine series, which is a high output version of the M50.
Design
thumb|right|Initial version of the M50 (prior to 1992 Technical Update)
A significant advance over its M20 predecessor, the M50 features dual overhead camshaft (DOHC) with four valves per cylinder (the M20 has a single overhead camshaft with 2 valves per cylinder), coil-on-plug ignition, a knock sensor and a lightweight plastic intake manifold. Both engines use an iron block with an aluminum alloy head. The redline is 6,500 rpm for the M50B25 and 6,750 rpm for the M50B20 (7,000 rpm for S50 models), the same as the final version of the M20.
The location of the oil pan (sump) varies according to the model the M50 is installed in. It is in the front on the E34 5 Series (like the M20), whereas it is in the rear on the E36 3 Series.
Models
{|class="wikitable sortable"
|-
!Engine!!Displacement!!Power!!Torque!! Years
|-
!M50B20
|rowspan=2||| <br/> at 6,000 rpm || <br/> at 4,700 rpm || 1990-1992
|-
!M50B20TÜ
| <br/> at 5,900 rpm || <br/> at 4,200 rpm || rowspan="2" | 1992-1996
|-
!M50B24TÜ
||| <br/> at 5,900 rpm || <br/> at 4,200 rpm
|-
!M50B25
|rowspan=2||| <br/> at 6,000 rpm || <br/> at 4,700 rpm || 1990-1992
|-
!M50B25TÜ
| <br/> at 5,900 rpm || <br/> at 4,200 rpm || 1992-1996
|-
!S50B30 (EU)
| rowspan="3" | || <br/> at 7,000 rpm || <br/> at 3,500 rpm || 1992-1995
|-
!S50B30 (US)
| <br/> at 6,000 rpm || <br/> at 4,250 rpm || 1994-1995
|-
!S50B30GT
| <br/> at 7,100 rpm || <br/> at 3,900 rpm || 1994-1995
|-
!S50B32
| || <br/> at 7,400 rpm || <br/> at 3,250 rpm || 1995-2000
|}
M50B20
thumb|M50 engine in BMW Museum
The M50B20 was introduced with the 1990 520i. It has a bore of , a stroke of and produces . The compression ratio is 10.5:1.
Applications:
- 1990-1992 E34 520i
- 1991-1995 E36 320i
M50B20TÜ
The M50B20 was updated with single VANOS in 1992. Peak torque became available at 4,200 rpm. It is based on the M50B25TÜ with the stroke reduced to and produces at 5,900 rpm and at 4,200 rpm. The compression ratio is 10.5:1.
Applications:
- 1993-1995 E36 325iA/2.4
- 1992-1996 E34 525iA/2.4
M50B25
The M50B25 was introduced with the 1990 525i and 525ix. It has a bore of , a stroke of and produces at 6,000 rpm and at 4,700 rpm.
|configuration= Straight-6
|valvetrain =DOHC, with VVT
|head =Aluminium
|block =Cast iron
|predecessor= None
|successor=BMW S54
|fueltype=Petrol
|displacement=<br>
| bore = <br>
| stroke = <br>
The S50 is the high performance version of the M50 which was used in the E36 M3, replacing the four-cylinder BMW S14 engine used in the E30 M3. Like the M50, the S50 has an iron block and aluminum head with four valves per cylinder.
In the United States, a less powerful engine called the "S50B30US" was used, which shares more in common with the regular M50 engine than the other S50 versions.
S50B30
The S50B30 was used in most countries, except for the United States. The S50B30 produces , has a bore of , a stroke of and a compression ratio of 10.8:1. The redline is 7,200 rpm. The S50 has an individual throttle body for each cylinder, single-VANOS (variable valve timing on the intake camshaft), Bosch Motronic M3.3 engine management and redesigned intake and exhaust systems.
The limited edition "M3 GT" model from 1995 produced . It had different camshafts and a redesigned sump and oil pump.
Applications:
- 1992-1995 E36 M3 (except for U.S.)
S50B30US
In the United States, the 1994-1995 model years of the E36 M3 are powered by the S50B30US, a engine which produces . This engine is more closely related to the standard M50 engine and has the same compression ratio as the M50B25TÜ,
The S50B30US motor was created as a compromise to make the E36 M3 a reality in the United States. Unlike in Europe, the E30 M3 was considered a business failure in America. American customers did not see the value proposition of this vehicle compared to a 325i, and due to this, E30 M3s sold poorly in the United States with just over 5,000 units sold. For comparison, the 325i sold just under 350,000 units. Because of this, BMW of North America planned on canning the M brand in the US, and with it any plans to bring the E36 M3 to America. This was until an editor for the BMW Car Club of America, Bob Roehmer, encouraged BMW CCA members to mail BMW of North America letters asking them to bring the car to the United States. This worked, with many BMW CCA members promising to buy an E36 M3 if it was brought to the United States at a reasonable price. To meet this caveat, Erik Wensberg, the manager of the BMW M Brand in North America, decided to remove the European spec S50 motor, and replace it with a M50 motor that was tuned by the BMW M division. This motor would become the S50B30US, and would only be found in American spec E36 M3s.
In 1996, the S50B30US was replaced by the BMW S52 engine (in the United States and Canada only). This motor was a derivative of the M52, and while it maintained the same 240 horsepower as the S50B30US, it gained 11 ft lbs of torque and increased displacement from 3000cc to 3200cc
Applications:
- 1994-1995 E36 M3 (U.S. only)
S50B32
In 1995, the S50B32 replaced the S50B30 in world markets. Power output increased to and the displacement increased to , due to an increased stroke of and a slight increase in bore to .
The S50B32 has double-VANOS (variable valve timing on both camshafts) and a secondary oil pick-up was added. The compression ratio is 11.3:1 and the redline is 7,600 rpm. Engine management is the Siemens MSS50, with 3 knock sensors.
Applications:
- 1995-1999 BMW M3 (E36) (except Canada and the United States)
- 1996-2000 BMW M Coupé and M Roadster (except Canada and the United States)
See also
- BMW engines