BMW M50

Design

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

M50B20

The 1991 cc M50B20 was introduced with the 1990 520i. It has a bore of 80 mm, a stroke of 66 mm and produces 110 kW. The compression ratio is 10.5:1.

Applications:

• 1990-1992 E34 520i
• 1991-1995 E36 320i

{{anchor|M50B20TU|M50B20TÜ}} M50B20TÜ

The M50B20 was updated with single VANOS in 1992. Peak torque became available at 4,200 rpm. It produces 110 kW at 5,900 rpm and 190 Nm at 4,200 rpm. The compression ratio was raised to 11.0:1.

Applications:

• 1992-1994 E36 320i
• 1992-1996 E34 520i

{{anchor|M50B24TU|M50B24TÜ}} M50B24TÜ

This is a 2394 cc engine used in the Thailand and Oceanian markets. It is based on the 2494 cc M50B25TÜ with the stroke reduced to 72 mm and produces 138 kW at 5,900 rpm and 240 Nm 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 2494 cc M50B25 was introduced with the 1990 525i and 525ix. It has a bore of 84 mm, a stroke of 75 mm and produces 141 kW at 6,000 rpm and 245 Nm at 4,700 rpm. The compression ratio is 10.0:1.

Applications:

• 1990-1992 E34 525i, 525ix
• 1991-1992 E36 325i, 325is

{{anchor|M50B25TU|M50B25TÜ}} M50B25TÜ

The M50B25 was updated with single VANOS in 1992, resulting in peak torque becoming available at 4,200 rpm. It produces 141 kW at 5,900 rpm and 250 Nm at 4,200 rpm. The compression ratio was increased to 10.5:1.

Applications:

• 1993-1995 E36 325i, 325is
• 1992-1996 E34 525i, 525ix

M50B30TÜ concept

In 1993, BMW Individual created a concept of BMW E34 530iX called Enduro Touring. Only one car was produced, having an up-sized variant of M50B25TÜ engine. Bore and stroke was increased and the total displacement of 3.0 was achieved. The power and torque both increased to 181 kW and 316 Nm respectively.

S50

3201 cc 86.4 mm 91 mm 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 210 kW, has a bore of 86 mm, a stroke of 85.8 mm 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 220 kW. 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 2990 cc engine which produces 179 kW. 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 236 kW and the displacement increased to 3201 cc, due to an increased stroke of 91 mm and a slight increase in bore to 86.4 mm.

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)

Notes

References

References

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