BMW M21

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M21
BMW M21D24 engin PL.JPG
Overview
Manufacturer BMW
Production 1983–1991
Combustion chamber
Configuration Inline-6
Displacement 2443 cm³
Cylinder bore 80 mm
Piston stroke 81 mm
Cylinder block alloy Cast iron
Valvetrain OHC
Compression ratio 22:1
Combustion
Turbocharger Garret (85 kW engines only)
Fuel system Swirl chamber injection
Fuel type Diesel fuel
Cooling system Water-cooled
Output
Power output 63 – 85 kW
Torque output 152 – 220 Nm
Chronology
Predecessor None
Successor M51

The BMW M21 is a six-cylinder-inline-diesel engine developed by the bavarian engine manufacturer BMW. The engine with swirl chamber injection is based on the otto engine M20[1] and was produced for BMW by the upper Austrian Steyr engine plant from 1983 to 1991. It was succeeded by the M51.[2]

Background[edit]

In the 1970s BMW decided to develop an engine, which would both be powerful and have a good fuel economy. This was caused by the oil crisis in 1973. In 1975 a group of BMW engineers started working on the M21 diesel engine, the otto engine M20 was taken as the basis. In 1983 at the IAA, the first passenger car was shown to the public which made use of the 85 kW M21. It was the E28 524td, which has a top speed of 180 km/h and reaches 100 km/h in 12,9 s. This 5er-BMW was the fastest series production diesel car in the world back in 1983. It has a fuel economy of 7,1 l /100 km.[2]

Technical description[edit]

The M21 is a water-cooled[3] and swirl-chamber-injected six-cylinder-inline-diesel-engine with a cast iron block and OHC valvetrain. The camshaft is driven by a belt,[2] each cylinder has one inlet and one outlet valve.[1] Compared to the otto engine M20, the M21 has reinforced connecting-rods, cylinder heads, pistons, valves[2] and a reinforced crankshaft[1] with seven[3] bearings.

For faster engine startup the M21 has a glowplug system called instant start, which reduces the time to reach starting temperature compared to similar diesel engines.[2] The fuel is injected into swirl chambers.[1]

A Garret turbocharger[4] is used (without an intercooler). Initially, the M21 was only available as a turbocharged engine. In 1985, BMW introduced a naturally aspirated version of the M21, which was popular in countries with a high motor vehicle tax.[2]

Initially, the fuel injection system was controlled mechanically. In 1987, this system was replaced by an electronic diesel control system,[5][6] which increased the torque output by 10 N·m (7 lb·ft). The updated engine has a smaller turbocharger, which improves response.[1]

Models[edit]

Engine Aspiration Power Torque Redline Year
M21D24[3] turbocharged 85 kW (114 hp) at 4800 min−1 210 N·m (155 lb·ft) at 2400 min−1 5350 min−1 1983
220 N·m (162 lb·ft) at 2400 min−1 5350 min−1 1987
natural 63 kW (84 hp) at 4600 min−1 152 N·m (112 lb·ft) at 2500 min−1 5150 min−1 1985

Applications:

See also[edit]

References[edit]

  1. ^ a b c d e Andreas in Bimmer: Die BMW-Sportdiesel: Von 524td E28 über 530d E39 bis BMW M550d F10, published at the 21st of January 2012, retrieved at the 9th of April 2015. (german)
  2. ^ a b c d e f Ronan Glon in RanWhenParked.net: 30 years ago: BMW introduces its first diesel engine, published at the 22nd of Juli 2013, retrieved at the 9th of April 2015.
  3. ^ a b c Meyer Motoren: BMW M21. Retrieved at the 9th of May 2016. (german)
  4. ^ Auto Motor und Sport: Der zweite 5er von BMW: Die Baureihe E28 Der unscheinbare Revoluzzer, retrieved at the 9th of April 2015. (german)
  5. ^ BMW M21 engine page. Retrieved at the 9th of May 2016.
  6. ^ E30 Zone- M21. Retrieved at the 3rd of January 2017.
  7. ^ a b Turbo Diesel Lincoln Continental M21. Retrieved at the 3rd of January 2017.
  8. ^ Meet the Vixen RV, BMW 2 Series Active Tourer’s American Ancestor. Retrieved at the 3rd of January 2017.

External links[edit]