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The BMW M50 inline 6-cylinder engine was used in BMW models like the E34 5 Series Sedan and the E363 Series. The successor to the M50 was the M52 engine.

The M50 was produced in 2.0 (M50B20) and 2.5 liter (M50B25) configurations. A "Technical Upgrade"was issued in 1992 when the M50 because BMW's first engine to utilize the VANOS technology.Engines with a designation of M50TU are VANOS engines.

The M50 was a 24-valve engine utilizing BMW's 4-valve per cylinder technology. For each of thetwo camshafts, the bearings and the bucket-type tappets, with integrated hydraulic clearanceadjustment, were carried in a demountable aluminum tappet block that was attached to the headby the same studs that held down the caps for the cam bearings. When this was removed therewas good access to the cylinder-head bolts, despite the short cylinder spacing and the narrowvalve angle (39.5 degree included angle). The exhaust camshaft was driven by a single-row chain.From a smaller sprocket and another single-row chain, the exhaust cam drove the inlet cam, anarrangement that reduced the engine's installed height.

The intake system was made entirely of reinforced plastic using the core melt-out procedure. Thiswas the world's first mass-production application of this technology. The belt-driven intermediateshaft previously used to drive the distributor and the oil pump, was dispensed with. The oil pumpwas not driven by a short chain from the crankshaft, as was the case in the M10 engine. Ignitionwas by a new system with an individual ignition coil for each cylinder, known as "static high-voltage distribution."

Like its predecessor the M20, the M50's cylinder center distance was 91 mm. M20 bore and strokedimensions were also kept for the 2.0 and 2.5-liter versions, for which power output was 150 bhpand 192 bhp respectively. The engine was designed for Super petrol. Until this time, engines forcatalytic converters had been designed for use with Regular unleaded in accordance with its wideravailability.

In 1992 production began of further-developed versions of this engine which offered lower fuelconsumption and increased torque. At the same time, the new evolutions contributed to areduction in exhaust emissions and a further improvement in the engine's running characteristics. Akey role was played by the VANOS variable-cam-timing system, which made a positive contributionto all four criteria.

Measures were taken to reduce friction in the valve gear and pistons. As well, the use of thelongest possible connecting rods for each capacity optimized fuel consumption and enhancedsmooth running. The use of electronic knock detection also contributed.

Engine Codes

Engine Specifications

Item/Measurement M50B20 M50B20 M50B25 M50B25

Vehicle 520i 520i 525i 525i

Number of Cylinders 6 6 6 6

Layout in-line in-line in-line in-line

Installation 30� inclined right30� inclinedright

30� inclined right 30� inclined right

Coolant liquid liquid liquid liquid

Crankcase/BlockMaterial

perlit. cast iron cast iron perlit. cast iron cast iron

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Materialperlit. cast iron cast iron perlit. cast iron cast iron

Crankshaft one-piece one-piece one-piece one-piece

Main Bearings 7 7 7 7

Weight (kg) 194 198 194 198

Valve Layout dohc dohc dohc dohc

Camshaft Drive simplex chain simplex chain simplex chain simplex chain

Camshaft Bearings 7 each 7 each 7 each 7 each

Valves per Cylinder 4 4 4 4

Cylinder CenterDistance (mm)

91 91 91 91

Displacement (liters) 1.991 1.991 2.494 2.494

Bore/Stroke (mm) 80/66 80/66 84/75 84/75

Stroke/Bore Ratio 0.83 0.83 0.89 0.89

Piston Speed (ms) 13.0 13.0 14.8 14.8

Valve Timing (IO/IC) 24�btdc/36�abdc 9�btdc/39�abdc 19�btdc/41�abdc 4�btdc/44�abdc

(EO/EC) 38�bbdc/10�atdc 39�bbdc/9�atdc 35�bbdc/13�atdc 35�bbdc/13�atdc

At Valve Lift (mm) ER-ER ER-ER ER-ER ER-ER

Valve Lift I/E (mm) 9.7/8.8 9.0/9.0 9.7/8.8 9.0/9.0

Connecting RodLength (mm)

135 145 135 140

Connecting Rod Ratior/l

0.24 0.23 0.28 0.27

Compression Ratio 10.5:1 11.0:1 10.0:1 10.5:1

Fuel Super LF Norm-Sup Plus LF Super LF Norm-Sup Plus LF

Power Output(bhp@rpm)

150/5900 150/5900 192/5900 192/5900

Power per Liter(bhp/liter)

75.34 75.34 76.98 76.98

Power/Weight Ratio(kg/bhp)

1.29 1.32 1.01 1.03

Torque (mkg@rpm) 19.4/4700 19.4/4200 25/4700 25.5/4200

Torque per Liter(mkg/liter)

9.73 9.73 10.01 10.22

Mixture Preparation fuel injection fuel injection fuel injection fuel injection

Maker Bosch Siemens Bosch Siemens

Designation DME M3.1 DME MS41 DME M3.1 DME MS41

Ignition integrated integrated integrated integrated

Ignition Advance map map map map

Generator 12 V/1120 W 12 V/1120 W 12 V/1260 W 12 V/1260 W

Supercharging - - - -

Miscellaneous - VANOS, KD - VANOS, KD

Year of Introduction 1989 1992 1989 1992

source: BMW Motoren, Dr. Karlheinz Lange

Links

Performance Parts for your BMW M50 engine.

Repair Tips to keep your BMW M50 in top shape.

BMW engine and model codes.

Engine Technology:

Valvetronic.

VANOS.

Engine Cleaning. Be careful with your BMW M50 engine.

Wallpaper of BMW engines. More...

More engine links.

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More engine links.

BMW E36 M3 CSL Lightweight had an M50 engine.

Story of an engine swap: M50 engine into popular E30 body style.

M50 engines use a water pump with a plastic impeller. After 80k this can fail and leave littlebits all around the cooling system. Replace it with the later metal style pump before it fails.M50s don't seem to like the cooling system being neglected, you need a fluid change every 2years at least. - John G. Burns

John G. Burns E36 page has some tips for M50 engines.

Koala Motorsport page on M50 overheating has a procedure for replacing the water pump.

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