The BMW M50 inline 6-cylinder engine was used in BMW models
like the E34
5 Series Sedan and the
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 the two camshafts, the bearings and
the bucket-type tappets, with integrated hydraulic clearance adjustment,
were carried in a demountable aluminum tappet block that was attached to
the head by the same studs that held down the caps for the cam bearings.
When this was removed there was good access to the cylinder-head bolts,
despite the short cylinder spacing and the narrow valve 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, an arrangement that reduced the engine's installed
The intake system was made entirely of reinforced
plastic using the core melt-out procedure. This was the world's first
mass-production application of this technology. The belt-driven
intermediate shaft previously used to drive the distributor and the oil
pump, was dispensed with. The oil pump was not driven by a short chain
from the crankshaft, as was the case in the M10 engine. Ignition was 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 stroke dimensions were also kept
for the 2.0 and 2.5-liter versions, for which power output was 150 bhp and
192 bhp respectively. The engine was designed for Super petrol. Until this
time, engines for catalytic converters had been designed for use with
Regular unleaded in accordance with its wider availability.
In 1992 production began of further-developed versions
of this engine which offered lower fuel consumption and increased torque.
At the same time, the new evolutions contributed to a reduction in exhaust
emissions and a further improvement in the engine's running
characteristics. A key role was played by the
VANOS variable-cam-timing system,
which made a positive contribution to all four criteria.
Measures were taken to reduce friction in the valve
gear and pistons. As well, the use of the longest possible connecting rods
for each capacity optimized fuel consumption and enhanced smooth running.
The use of electronic knock detection also contributed.