BMW M21

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BMW
M21 as a turbo engine (1986)

M21 as a turbo engine (1986)
M21
Production period: 03.1983-12.1992
Manufacturer: BMW
Working principle: diesel
Motor design: Row , six-cylinder
Valve control: OHC
Displacement: 2443 cm 3
Mixture preparation: Swirl chamber injection
Engine charging: Partly turbocharged
Power: 63 - 85 kW
Max. Torque: 152-220 Nm
Dimensions: approx. 250 kg
Previous model: none
Successor: BMW M51

The BMW M21 is a six-cylinder in- line diesel engine from the Bavarian engine manufacturer BMW . The engine with swirl chamber injection was from the gasoline engine M20 developed and in March 1983 the Upper Austrian Steyr in series production for BMW. It was replaced in 1991 by the successor M51 . A total of 174,407 units were built, the last M21 was assembled on December 17, 1992.

background

In the wake of the oil crisis in the 1970s, BMW decided to develop an engine that represented a compromise between performance and low consumption. In 1974 BMW initially licensed the FM direct injection process for diesel engines from MAN . Starting in 1975, BMW put together a team of developers who developed a diesel engine from the M20 petrol engine, albeit not with direct injection but with swirl chamber injection . In autumn 1978 the first prototype of the M21 engine was presented to the press. Its technical data already correspond to that of the later production model. The first E28 524td powered by the M21 engine was presented at the Frankfurt International Motor Show in 1983 . The 5 Series reached a top speed of 180 km / h and sprinted from 0 to 100 km / h in 12.9 seconds. This made the E28 the fastest series-produced sedan in the world powered by a diesel engine. The fuel consumption of this E28 was 7.1 liters per 100 km. In 1986 Bosch presented the first electronic control unit for diesel engines Bosch EDC (Electronic Diesel Control), the M21 for the E28 was the first diesel engine worldwide to receive this system.

Structure and technology

Functional principle of fuel injection in the BMW M21

The M21 is a water-cooled six-cylinder in-line engine made of gray cast iron with OHC valve control and swirl chamber injection . The cylinder head is designed according to the cross-flow principle . The camshaft is driven by a toothed belt and actuates two valves per cylinder. The camshaft also drives the oil pump via a secondary shaft. Compared to the M20 engine, the M21 has reinforced connecting rods, pistons, valves, a reinforced cylinder head and a reinforced crankshaft with seven bearings and twelve counterweights. The M21 was equipped with a system called Instant Start , which reduces the pre-glow time compared to comparable diesel engines. The idle speed is regulated depending on the temperature. In versions built from 1983 to 1987, fuel injection is controlled mechanically and in supercharged versions of the M21 engine built from 1987 onwards by a digital engine control unit , which ensures better torque than conventional injection control. The injection pump is a distributor injection pump in which the fuel pump is integrated. It is driven by the toothed belt. The engine has an overrun cut-off . Some variants of the M21 engine are charged by means of a Garrett turbocharger (type T03) without intercooler . The engine with a digital control unit has a slightly smaller turbocharger that improves the response. 1985 BMW put the M21 engine as suckers by the high especially in countries with road tax was popular. The naturally aspirated engine received the digital engine control unit only in 1989. The charged M21 has 85% of the maximum torque at 1700 min −1 . In addition to the water cooler, the M21 with turbocharger also has an engine oil cooler. The electric starter has an output of 2200 W. Like the water pump, the generator is driven by the toothed belt. The power steering pump has a separate V-belt.

Technical specifications

Torque and power development BMW M21
Technical specifications
engine Bore × stroke Displacement power Torque Maximum speed compression Engine charging Engine control Production period
M21D24 80 × 81 mm 2443 cc 85 kW at 4800 rpm 210 Nm at 2400 rpm 5300 rpm 22: 1 turbocharger Mechanically 09.1983-08.1987
220 Nm at 2400 rpm 5300 rpm 22: 1 Bosch EDC 1987-1992
63 kW at 4600 rpm 152 Nm at 2500 rpm 5150 rpm 22: 1 - Mechanically 09.1985-08.1987
- Bosch EDC 1989-1992

Operating fluids

The M21 is designed for operation with diesel fuel according to DIN 51601 with a minimum cetane number of 45. Marine diesel and heating oil are not suitable as fuels. In exceptional cases, fuel with a cetane number lower than 45 can also be used, but in such cases a continuous full load of the engine should be avoided. Engine oil of the API specification CD should be used.

criticism

The editorial team of auto motor und sport gave a positive opinion on the M21:

"... not only the continuous power development and the temperament of the youngest BMW offspring, which is refreshing temperament for diesel conditions, but rather the fact that in terms of noise emissions and smoothness compared to the gasoline-powered BMW six-cylinder engines there are hardly any compromises"

- quoted from Kai Klauder

In 1986, Andreas Borchmann criticized the naturally aspirated M21 engine in the BMW E28 rather negatively:

“The petrol engines from BMW are among the finest. That can only be said to a limited extent for the diesel engine. What doesn’t leave the most spirited impression in the compact 3 Series, cannot do better in the 155 kg heavier 5 Series. In fact, the man from Munich is starting to move slowly. Amazing for a diesel: The six-cylinder is weak. Not much is happening under 3000 tours. That is why it has to be switched frequently in order to swim halfway quickly in traffic. The positive side of the six-cylinder diesel: It remains quite quiet even at high engine speeds. In this discipline, the BMW engine belongs to the top diesel. "

- Andreas Borchmann

Applications

Remarks

  1. ↑ The manual speaks of a camshaft drive via a roller chain, but the sectional drawing there shows a toothed belt. (Compare Chapters 6–03). Etzold also writes that the M21 has a toothed belt; The M10 and M30 have a single roller chain . (see Etzold, p. 14).

Individual evidence

  1. ^ Hans J. Schneider: BMW 5 Series - technology + types, models up to 1997 ; Bielefeld 2007, ISBN 978-3-7688-5789-5 , p. 91
  2. ↑ a b c d e Etzold, p. 14
  3. ↑ Production of the first BMW diesel engine
  4. ↑ a b c d e f g h i Ronan Glon in RanWhenParked.net : 30 years ago: BMW introduces its first diesel engine , published on July 22, 2013, accessed on April 9, 2015 (English)
  5. ↑ BMW archive: BMW M21D25 automobile engine (115 hp) . Retrieved May 31, 2017
  6. ↑ Last M21 motor installed . In: BMW AG (Ed.): Bayernmotor . BMW employee newspaper. No.  2 , February 1, 1993, ZDB -ID 558618-5 , p. 8 ( bmw-grouparchiv.de [accessed on February 1, 2017]).
  7. ^ MAN Nutzfahrzeuge AG: Performance and way: On the history of MAN commercial vehicle construction. Springer-Verlag. Berlin, Heidelberg. 1991. ISBN 978-3-642-93490-2 . P. 506
  8. ^ Hans J. Schneider: BMW 5 Series - technology + types, models up to 1997 ; Bielefeld 2007, ISBN 978-3-7688-5789-5 , p. 90
  9. ^ Brian Long: Zero Carbon Car: Green Technology and the Automotive Industry, Crowood, 2013, ISBN 978-1-84797-514-0 .
  10. ↑ a b c Meyer Motoren: BMW M21
  11. ↑ a b c d e BMW: 524d 524td: Diesel with dynamism and style . February 1987. Pages 21 and 22
  12. ↑ a b c d e Andreas in Bimmer : The BMW Sportdiesel: From 524td E28 to 530d E39 to BMW M550d F10 , published on January 21, 2012, accessed on April 9, 2015
  13. ↑ a b c BMW M21 engine page . Retrieved May 9, 2016.
  14. ↑ Operating Instructions 6–04
  15. ↑ a b c d e Auto motor und sport : The second 5 Series from BMW: The E28 series The inconspicuous revolutionary , accessed on April 9, 2015
  16. ^ Hans J. Schneider: BMW 5 Series - technology + types, models up to 1997 ; Bielefeld 2007, ISBN 978-3-7688-5789-5 , p. 92
  17. ↑ Operating Instructions 4–05
  18. ↑ Operating Instructions 6–13
  19. ↑ Operating Instructions 6–24
  20. ↑ Operating Instructions 6–07
  21. ↑ Etzold, p. 13
  22. ↑ Operating Instructions 1–14
  23. ↑ Operating Instructions 4–02
  24. ↑ Operating Instructions 4–10
  25. ↑ Andreas Borchmann: Does BMW already dies as well as Mercedes? , in Auto Bild, 52/1986, p. 44
  26. ↑ BMW Group works newspaper Steyr October 2016, p. 4

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