BMW M20 engine | |
---|---|
Overview | |
Production | 1977–1993 |
Layout | |
Configuration | Straight-6 |
Displacement | 2.0 L (1,991 cc) 2.3 L (2,316 cc) 2.5 L (2,494 cc) 2.7 L (2,693 cc) |
Cylinder bore | 80 mm (3.15 in) 84 mm (3.31 in) |
Piston stroke | 66 mm (2.60 in) 75 mm (2.95 in) 76.8 mm (3.02 in) 81 mm (3.19 in) |
Block material | Cast iron |
Head material | Aluminium |
Valvetrain | SOHC |
Combustion | |
Fuel type | Petrol |
Chronology | |
Predecessor | None |
Successor | BMW M50 |
The BMW M20 is a SOHC straight-six petrol engine which was produced from 1977 to 1993. It was introduced eight years after the larger BMW M30 straight-six engine, which remained in production alongside the M20. [1]
The first cars to use the M20 were the E12 5 Series and the E21 3 Series. The initial M20 model had a displacement of 2.0 L (122 cu in), with later versions having displacements of up to 2.7 L (165 cu in). [2]
The M20 began to be phased out following the introduction of the M50 engine in 1990. The final M20 engines were fitted to the E30 3 Series wagon (estate) and convertible model built in April 1993. [3]
The M20 was the basis for the BMW M21 diesel engine. [4] It is also loosely related to the BMW M70 V12 petrol engine.
By the 1970s, BMW felt the need for a six-cylinder engine smaller than the BMW M30, to use in the 3 Series and 5 Series. [5] : 92 The resulting M20 had a displacement of 2.0 L (122 cu in), BMW's smallest straight-six engine of its day. BMW presented the M20 engine at the 1977 IAA as a 90 kW 2.0-litre Solex 4A1 carburetted version, and as a 105 kW 2.3-litre K-Jetronic multi-point injected version. [6] Later versions had displacements up to 2.7 L (165 cu in). The M20 was used in the E12 5 Series, E21 3 Series, E28 5 Series, E30 3 Series and E34 5 Series.
Early versions of the M20 were sometimes referred to as the "M60", [7] [8] although the M60 designation has since been re-used for a V8 engine produced from 1992 to 1996.
As per the M30, the M20 has an iron block, aluminium head and a SOHC valvetrain with 2 valves per cylinder. [9] It has a traditional rocker arm design and no hydraulic tappets. [10] The major differences to the M30 are:
Version | Displacement | Power | Torque | Years |
---|---|---|---|---|
M20B20 | 1,991 cc (121.5 cu in) | 90 kW (122 PS; 121 hp) [lower-alpha 1] at 6,000 rpm [15] | 163 N⋅m (120 lb⋅ft) at 4,000 rpm | 1977-1982 |
92 kW (123 hp) at 5,800 rpm | 170 N⋅m (125 lb⋅ft) at 4,000 rpm | 1982-1984 | ||
174 N⋅m (128 lb⋅ft) at 4,000 rpm | 1984-1987 | |||
95 kW (127 hp) at 6,000 rpm | 164 N⋅m (121 lb⋅ft) at 4,300 rpm | 1986-1992 | ||
M20B23 | 2,316 cc (141.3 cu in) | 105 kW (143 PS; 141 hp) at 5,300 rpm [15] | 190 N⋅m (140 lb⋅ft) at 4,500 rpm | 1977-1982 |
102 kW (137 hp) at 5,300 rpm | 205 N⋅m (151 lb⋅ft) at 4,000 rpm | 1982-1983 | ||
110 kW (148 hp) at 6,000 rpm | 205 N⋅m (151 lb⋅ft) at 4,000 rpm | 1983-1987 | ||
M20B25 | 2,494 cc (152.2 cu in) | 126 kW (169 hp) at 5,800 rpm | 226 N⋅m (167 lb⋅ft) at 4,000 rpm | 1985-1990 |
125 kW (168 hp) at 5,800 rpm | 226 N⋅m (167 lb⋅ft) at 4,300 rpm | 1987-1992 | ||
M20B27 | 2,693 cc (164.3 cu in) | 92 kW (123 hp) [lower-alpha 2] at 4,250 rpm | 240 N⋅m (177 lb⋅ft) at 3,250 rpm | 1982-1985 |
90 kW (121 hp) [lower-alpha 3] at 4,250 rpm | 230 N⋅m (170 lb⋅ft) at 3,250 rpm | 1985-1987 | ||
95 kW (127 hp) at 4,250 rpm | 240 N⋅m (177 lb⋅ft) at 3,250 rpm | 1985-1988 |
The first models to use the M20 were the E12 520/6 and the E21 320/6, which used a 1,991 cc (121 cu in) version known as the M20B20VE or M60/2. [18] [19] This engine uses a bore of 80 mm (3.15 in) and a stroke of 66 mm (2.60 in). [18] A Solex 4A1 four-barrel carburetor was used in the M20B20VE ("VE" is for vergaser- "carburettor" in German), [20] and it has a compression ratio of 9.2:1 and a redline of 6,400 rpm.
The M20 first became fuel-injected in 1981, [21] with Bosch K-Jetronic used in a 92 kW (123 hp) version called the M20B20KE. [22] The compression ratio was raised to 9.9:1.
In September 1982 (coinciding with the release of the E30 3 Series), the fuel injection was updated to LE-Jetronic with a redline of 6,200 rpm. Other upgrades included a larger port (known as "731") cylinder head, a lighter block and new manifolds.[ citation needed ] The "M60" designation was dropped and this version was known as the M20B20LE. [23]
In 1987, the M20B20 was again revised with the addition of Bosch Motronic engine management, a catalytic converter and a compression ratio of 8.8:1. [24] [23]
The M20B20 was not sold in North America.
Applications:
In March 1978 (six months after the M20 was launched), a fuel-injected and larger displacement version known as the M20B23KE (or M60/5) was introduced. This version uses the same head (known as "200") and block as the 2.0 litre version but a longer 76.8 mm (3.02 in) stroke crank. The bore is 80 mm (3.15 in) and it has a capacity of 2,316 cc (2.3 L). Fuel injection was K-Jetronic, the compression ratio is 9.5:1, the power output is 105 kW (143 PS; 141 hp) [15] and the redline is 6,400 rpm. [20]
The 1982 version used LE-Jetronic, the 731 cylinder head, a compression ratio of 9.8:1 and the other upgrades as the per the 2.0 litre version. This version is called the M20B23LE and has a power output of 102 kW (137 hp).
In September 1983, the M20B23LE's fuel-injection, exhaust and camshaft were upgraded and power increased to 110 kW (148 hp) with a redline of 6,500 rpm. The 102 kW (137 hp) version continued to be available in certain markets with strict emissions regulations (such as Switzerland) until replaced by the 325i. [29]
The M20B23 versions were not sold in North America.
Applications:
In 1985, the M20B25 replaced the M20B23. The M20B25 has a capacity of 2,494 cc (152.2 cu in) and initially produced 126 kW (171 PS; 169 hp) (without a catalytic converter). [31] It has an upgraded cylinder head (known as "885"), a bore of 84 mm (3.31 in), a stroke of 75 mm (2.95 in), a compression ratio of 9.4:1, a redline of 6,500 rpm and uses Bosch Motronic 1.1 engine management. [32] [23]
In 1987, a catalyzed model with Motronic 1.3 engine management was introduced. [33] [23] The compression ratio was reduced to 8.8:1 but thanks to the more sophisticated electronics power remained nearly as before, at 125 kW (170 PS; 168 hp). The uncatalyzed engine was kept in production for Southern Europe and other markets where unleaded petrol was not regularly available.
Applications:
The M20B27 was designed for efficiency (thus the e for the Greek letter eta in 325e) and low-rev torque. [34] This is an unusual design strategy for a BMW straight-six engine, which are usually designed for power at high RPM. Compared with the M20B25, the stroke is increased from 75 to 81 mm (2.95 to 3.19 in), resulting in a capacity of 2,693 cc (164.3 cu in). [32] Since many markets tax cars based on engine displacement, the eta's larger displacement meant that it was not suitable for all markets. It was expressly developed with the American market in mind. As per the M20B25, the bore is 84 mm (3.31 in). To reduce friction and improve efficiency, the M20B27 changes include using the '200' version of the head (which has smaller ports), a different camshaft, four camshaft journals and softer valve springs. Due to these changes the rev limit on the M20B27 was reduced to 4,800 rpm. The initial version, called the M20B27ME, produces 92 kW (123 hp) and 240 N⋅m (177 lb⋅ft) at 3,250 rpm for models without a catalytic converter. [32] Models with a catalytic converter produce 90 kW (121 hp) and 230 N⋅m (170 lb⋅ft).
In the United States, BMW's corporate average fuel economy was at risk of not meeting requirements by 1984, primarily due to higher sales of their bigger, more expensive cars in the early 1980s. [35] The first car to use the M20B27 was the US market 528e in 1982. The compression ratio of the U.S. M20B27ME version was 9.0:1, compared with for cars sold elsewhere 11.0:1.
In 1985, the M20B27ME.E version was introduced, increasing power output to 95 kW (127 hp) despite a lower compression ratio of 10.3:1. [36]
In late 1987, the fuel injection was upgraded to Motronic 1.3 on the US market plastic bumper 325e and 528e 'Super Eta', [37] [38] the cylinder head changed to the "885" version, the compression ratio was reduced to 8.5:1 and the redline increased to 5,200 rpm. [39] Power output increased to 95 kW (127 hp) at 4,800 rpm.
In the early 1990s BMW South Africa used components from the Alpina C3 2.7 to produce an E30 specifically for Stannic Group N production car racing. The first iteration of this engine used in the E30 325iS produced 145 kW (194 hp) and the second revision, often referred to as "Evo2" or on the VIN plate as "HP2" produced 155 kW (208 hp).
Applications:
The BMW M30 is a SOHC straight-six petrol engine which was produced from 1968 to 1995. With a production run of 27 years, it is BMW's longest produced engine and was used in many car models.
The BMW M10 is a SOHC four-cylinder petrol engine which was produced from 1962-1988. It was BMW's first four-cylinder engine since the BMW 309 ended production in 1936 and was introduced in the New Class sedans.
The BMW M40 is an SOHC straight-four petrol engine which was produced from 1987–1994. It served as BMW's base model four-cylinder engine and was produced alongside the higher performance BMW M42 DOHC four-cylinder engine from 1989 onwards.
The BMW M50 is a straight-6 DOHC petrol engine which was produced from 1990 to 1996. It was released in the E34 520i and 525i, to replace the M20 engine.
The BMW M52 is a straight-6 DOHC petrol engine which was produced from 1994 to 2000. It was released in the E36 320i, to replace the M50. The BMW S52 engine is a high performance variant of the M52 which powered the American and Canadian market E36 M3 from 1996 to 1999.
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The BMW E23 is the first generation of the BMW 7 Series luxury cars and was produced from 1977 until 1986. It was built in a 4-door sedan body style with 6-cylinder engines, to replace the BMW 'New Six' (E3) sedans. From 1983 until 1986, a turbocharged 6-cylinder engine was available.
The BMW E24 is the first generation of BMW 6 Series range of grand tourer cars, which was produced from January 1976 to 1989 and replaced the BMW E9 coupé.
The BMW E30 is the second generation of BMW 3 Series, which was produced from 1982 to 1994 and replaced the E21 3 Series. The model range included 2-door coupe and convertible body styles, as well as being the first 3 Series to be produced in 4-door sedan and wagon/estate body styles. It was powered by four-cylinder petrol, six-cylinder petrol and six-cylinder diesel engines, the latter a first for the 3 Series. The E30 325iX model was the first BMW to have all-wheel drive.
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Motronic is the trade name given to a range of digital engine control units developed by Robert Bosch GmbH which combined control of fuel injection and ignition in a single unit. By controlling both major systems in a single unit, many aspects of the engine's characteristics can be improved.
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