BMW M20

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BMW
M20 in a BMW E30

M20 in a BMW E30
M20
Production period: 1976-1992
Manufacturer: BMW
Working principle: Otto
Motor design: R6
Valve control: SOHC
Displacement: 1990 cm 3
2316 cm 3
2494 cm 3
2693 cm 3
Mixture preparation: Carburettor or
manifold injection
Engine charging: no
Power: 88-126 kW
Dimensions: approx. 170 kg
Previous model: none
Successor: BMW M50

The BMW M20 is a passenger car gasoline engine from the Bavarian engine manufacturer BMW , which was manufactured from 1976 to 1990 in Munich and from 1982 to 1992 in Steyr . The M20 is designed as a six-cylinder in - line engine with a displacement of 2 to 2.7 liters . The M21 diesel engine is considered to be the "descendant" of the M20 engine . The M20 was originally referred to as the M60 , but the changeover to the new naming scheme at BMW and thus the change to the M20 took place in 1983.

Development and production

The BMW M20 was developed as a “small” six-cylinder in the mid-1970s, as the “large” six-cylinder BMW M30 , built from 1968 onwards, was not suitable for the BMW E21 due to its dimensions . The cylinder spacing of the M30 was 100 mm, for the M20 a cylinder spacing of 91 mm was chosen, which resulted in a reduction in the external dimensions. The basic features were designed by Alexander von Falkenhausen , and the engine was ready for series production under Dr.-Ing. Karlheinz Lange brought. Originally designed as a 2.3-liter engine, a 2-liter version followed on the German market, and a 2.7-liter version, the eta version, was available on the North American market from 1981. Since the performance of the eta engine fell short of customer expectations, BMW developed a more powerful 2.5-liter engine as the last unit in the M20 family. The eta engine was also offered on the German market from 1983. The 2-liter M20 was offered throttled with 88 kW especially for the Austrian market.

The BMW M20 was produced by BMW engine construction in Munich from 1976 and at the same time at the BMW engine plant in Steyr from 1982 . By April 1990, 1.7 million cylinder heads had been manufactured for the unit in Munich, whereby the production of the M20 engines in Munich was discontinued in favor of the successor, the BMW M50 . The M20 continued to be built in small numbers at the Steyr plant. The M20 cylinder head line ended in Steyr on November 27, 1992; the last M21 cylinder head was manufactured on February 14, 1992. The last engine in engine assembly M20 / 21 rolled off the production line on December 17, 1992 in Steyr. At that time, the BMW M20 had largely been replaced by the BMW M50 six-cylinder engine, which had been in production since 1990 and which was equipped with four-valve technology .

use

The BMW M20 was used for the first time under the designation M60 (according to the old version number system) from 1977 in the 320 (E21) and 520 (E12) . In the BMW 3 and 5 series models, the M20 replaced the four-cylinder M10 engines with a displacement of two liters, which had been built in their basic design since 1961 , whereby the M10 engines with smaller displacements remained in the range until 1988.

The M20 was used in the E30 sedan until 1991 and in the E30 convertible and touring until 1993. The E30 successor E36 received the M50 engines with 2.0 and 2.5 l displacement in the 320i and 325i models from the start of production in 11/1990.

From May 1990 the M20 in the BMW E34 (520i / 525i) was replaced by the M50 engine with hydraulic valve lifters and chain drive of the camshaft, the main innovation of which was the four-valve technology and the associated increase in performance.

technical description

Intake manifold of an M20B20 with double register carburetor Solex 4A1
Intake bridge of an M20B27 (eta version) with intake manifold injection, clearly recognizable the very long intake manifolds (silver-colored components)

The M20 is a vertical and slightly inclined in-line six-cylinder engine with an overhead camshaft , which is water-cooled and works according to the Otto process . It has a slightly short stroke , the bore is 80 mm, the stroke 76.8 mm or 66 mm. Later there was also an 84 mm bore with a 75 mm or 81 mm stroke. This results in the four displacement variants 2.0 l, 2.3 l, 2.5 l and 2.7 l with outputs from 88 kW (120 PS) to 126 kW (171 PS).

The engine block is made of gray cast iron. All engines have a cylinder spacing of 91 mm. The M20 is the first BMW engine with a cast crankshaft.

The cylinder head made of an aluminum alloy is one-piece and designed as a cross-flow cylinder head . For the first time at BMW, the overhead camshaft was driven with a toothed belt instead of a timing chain . The camshaft actuates two V-shaped hanging valves per cylinder via rocker arms .

For mixture preparation, depending on the time of construction, size and series, a double register carburetor Solex 4A1 (320/6 or 520/6) and later a mechanical ( K-Jetronic ) or an electronic ( L-Jetronic / Motronic ) intake manifold injection in the 320i models was used / 323i / 325i / 520i / 525i. Alpina , Schnitzer and Hartge offered the engine with a higher output of up to 154.5 kW (210 hp), with the M20 versions installed in the Alpina C2 and B3 having a displacement of 2.7 liters. Characteristic of the BMW M20 with manifold injection is the cast intake manifold and thus realized resonance charging , in which the natural oscillation of the air column operates in a narrow speed range as a slight charge. This intake manifold differs only minimally in the respective displacement variants. Larger changes were made to the eta versions (2.7 l), although they were not immediately visible.

Special features of the eta version

Torque curve eta motor

Compared to the conventional M20 engine, the eta engine has longer intake manifolds, modified valve timing and reduced friction values ​​thanks to measures such as softer valve springs, reduced piston ring preload and only four camshaft bearings. Due to the large displacement of 2.7 liters, the eta version has a significantly higher torque at low speeds. The maximum value of 178 Nm of the 2.0-l engine is achieved by the 2.7-l engine already below 1000 rpm, the maximum value is 240 Nm at 3250 rpm and thus roughly the same as that of the 528i or 528i . 728i offered "large" M30 six-cylinder with 2.8 liter displacement, which however achieves a significantly higher output (135 kW / 184 PS at 5400 rpm). Thanks to its Motronic control unit, which was technically highly developed in the 1980s, the eta engine achieves an exceptionally smooth engine run, good starting properties and low fuel consumption. However, since it does not correspond to the typical BMW character of high-speed engines, the market success of the eta models was limited, 305,982 units were produced. In 1986 the eta engine was revised. The rated power was increased to 95 kW by a modified cylinder head (from M20B25), the final speed was at 5300 min -1 raised.

Weak points

Engines built before 1989 have a cylinder head that is screwed to the engine block with hexagon bolts. The hex head bolts tend to break unexpectedly. Later models have Torx screws that are not affected by this problem.

Technical specifications

BMW M20B25 engine in the BMW 5 Series ( BMW E34 )
engine Displacement Bore × stroke compression Power at 1 / min Torque at 1 / min construction time
M20B20VE 1990 cm 3 80.0 mm × 66.0 mm 9.2: 1 90 kW (122 hp) at 6000 163 Nm (16.5 kpm) at 4000 1977-1982
M20B20 9.8: 1 92 kW (125 PS) at 5800 170 Nm (17.3 kpm) at 4000 1983-1985
9.8: 1 95 kW (129 hp) at 6000 174 Nm (17.7 kpm) at 4000 1985-1990
M20B20 cat 8.8: 1 95 kW (129 hp) at 6000 164 Nm (16.7 kpm) at 4300 1986-1992
M20B23 2316 cm 3 80.0 mm × 76.8 mm 9.8: 1 102 kW (139 PS) at 5300 205 Nm (20.9 kpm) at 4000 1983-09 / 1983
9.8: 1 110 kW (150 PS) at 6000 205 Nm (20.9 kpm) at 4000 09 / 1983-1985
9.5: 1 105 kW (143 hp) at 6000 176 Nm (17.9 kpm) at 4500 1978-1982
M20B25 2494 cm 3 84.0 mm × 75.0 mm 9.7: 1 126 kW (171 hp) at 5800 226 Nm (23.0 kpm) at 4000 1985-1986
M20B25 cat 8.8: 1 125 kW (170 hp) at 5800 222 Nm (22.6 kpm) at 4300 1986-1991
M20B27 2693 cm 3 84.0 mm × 81.0 mm 11.0: 1 92 kW (125 PS) at 4250 240 Nm (24.5 kpm) at 3250 1982-1985
10.2: 1 95 kW (129 hp) at 4250 240 Nm (24.5 kpm) at 3250 1985-1986
9.0: 1 90 kW (122 PS) at 4250 230 Nm (23.5 kpm) at 3250 1985-1987
8.5: 1 95 kW (129 hp) at 4800 230 Nm (23.5 kpm) at 3200 1987-1988

At 170 to 175 kg, the mass of the engines was between that of the four-cylinder engines of the M10 type and that of the large six-cylinder engines of the BMW M30 type.

Usage overview

Engine code (old scheme) Engine code Start of production End of production Power (DIN-PS) Power kW) Mixture preparation use
M60 / 2 M20B20VE 09/1977 1982 122 hp 90 kW Double register
carburetor Solex 4A1 		E21 320
E12 520
M60 M20B20KE 09/1981 07/1985 125 hp 92 kW K-Jetronic E30 320i
E28 520i
M60 M20B20LE 09/1982 07/1985 125 hp 92 kW LE-Jetronic E30 320i
E28 520i
M20B20LE 09/1982 07/1985 125 hp 92 kW L-Jetronic E30 320i
E28 520i
M20B20LE ? ? 120 hp 88 kW L-Jetronic E28 520i
M20B20 Cat 09/1986 1991 129 hp 95 kW Bosch Motronic DME1.1

Bosch Motronic DME1.3

E30 320i
E28 520i
E34 520i
M60 / 5 M20B23LE 1983 1985 139 hp 102 kW Bosch L-Jetronic E30 323i
M60 / 5 M20B23KE 02/1978 1982 143 hp 105 kW K-Jetronic E21 323i
M20B23LE 1983 1985 150 hp 110 kW Bosch L-Jetronic E30 323i
M20B25 1985 1986 171 hp 126 kW Bosch ME Motronic E30 325i / iX
M20B25 Cat 1986 1992 170 hp 125 kW Bosch DME 1.3 E30 325i / iX
Z1
E34 525i
M20B27ME 1983 1985 125 hp 92 kW Bosch DME ML1 E28 525e
M20B27ME.E 1985 1986 129 95 kW Bosch DME ML E28 525e
M20B27 Cat 1985 1987 122 hp 90 kW Bosch DME ML E30 325e
E28 525e
M20B27 Cat 1986 1988 129 hp 95 kW Bosch DME1.1 E30 325e
E28 525e

literature

Individual evidence

  1. ↑ a b c Etzold: This is how it's done (Volume 68) , p. 14
  2. ↑ BMW AG (Ed.): BMW M20B20 automobile engine (125 hp) . Retrieved February 19, 2018
  3. ↑ a b Schneider: BMW 5 Series - Technology + Types, Models up to 1997, ISBN 978-3-7688-5789-5 , p. 44.
  4. ↑ a b c BMW (Ed.): BMW M20B27 automobile engine (122 hp) , accessed on February 19, 2018
  5. ^ Bowen: BMW 3-Series (E30) Performance Guide 1982–1994 , p. 9
  6. ↑ a b c d BMW AG (Ed.): Operating Instructions, Service Booklet 518, 520i, 525e, 525i, 528i, 535i, M535i, 524td . August 1985, p. 150 (6-06) ( bmw-grouparchiv.de [accessed on October 10, 2017] archive signature AB-82-10).
  7. ↑ BMW AG (Ed.): Start of series production M20, 1st engine, Steyr. BMW AG, May 17, 1982, accessed on August 12, 2016 (archive number: UF-4064-1).
  8. ↑ 14 years of M20: An era is coming to an end . In: BMW AG (Ed.): Bayernmotor . BMW employee newspaper. No.  4 , April 2, 1990, ZDB -ID 558618-5 , p. 7 ( bmw-grouparchiv.de [accessed on August 11, 2016]).
  9. ↑ BMW AG (Ed.): Last cylinder head for M20 in the Steyr plant. BMW AG, November 27, 1992, accessed on August 12, 2016 (archive number: FF-3448-1).
  10. ^ BMW AG (ed.): The last M21 ZK is being built, Steyr. BMW AG, February 14, 1992, accessed on August 12, 2016 (archive number: UJ-1406-1).
  11. ↑ BMW AG (Ed.): Last engine M21 in engine assembly M 20/21. BMW AG, December 17, 1992, accessed on August 12, 2016 (archive number: FF-3450-1).
  12. ↑ BMW AG (ed.): BMW 323i (E21) . Retrieved February 19, 2018
  13. ↑ a b Etzold: So it's done (Volume 68) , p. 13
  14. ↑ BMW AG (ed.): BMW 325i (E30) . Retrieved February 19, 2018
  15. ↑ a b Karlheinz Lange: History of the engine - engine of history (BMW dimensions 1 + 2) . Ed .: BMW Mobile Tradition. 1st edition. tape 2 (1945-2000) , 1999, ISBN 3-932169-04-2 , Chapter 12: In-line engines from 1971, p. 256 .
  16. ↑ Bowen: BMW 3-Series (E30) Performance Guide 1982–1994 , p. 8
  17. ^ Schneider: BMW 5 Series - Technology + Types, Models up to 1997, ISBN 978-3-7688-5789-5 , pp. 100-101 and 202.
  18. ^ Bowen: BMW 3-Series (E30) Performance Guide 1982–1994 , p. 10
  19. ↑ Bowen: BMW 3-Series (E30) Performance Guide 1982–1994 , p. 24
Timeline of BMW gasoline engines for passenger cars since 1961
Number of cylinders Conception 1960s 1970s 1980s 1990s 2000s 2010s
0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th
3 1.5 l B38
4th (1.5–2.0 l) M10
M40
M42
M43
M44
N40
N42
N45
N46
N43
N13
N20
B48
High performance motor S14
6th Small six-cylinder (2.0-3.0 l) M20
M50
M52
M54
Large six-cylinder (2.5-3.5 l) M30
N52
N53
N54
N55
B58
High performance motor M88
S38
S50
S52
S54
S55
8th 3.0-4.4 l M60
M62
N62
N63
High performance motor S62
S63
S65
10 High performance motor S85
12 5.0-6.6 l M70
M73
N73
N74
High performance motor S70
Number of cylinders Conception 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th 9 0 1 2 3 4th 5 6th 7th 8th
1960s 1970s 1980s 1990s 2000s 2010s