het jaartal van de kop staat net boven het inlaatspruitstuk tussen cylinder 1 en 2.
Verder staat er ongeveer in het midden van het onderblok een rondje met een aantal getallen. (zo'n rondje waarmee ze meestal in de autoindustrie een productie periode aangeven)
En dan nu een epistel over onze trouwe vriend, de M20 motor
(niet gecontroleerd op waarheden maar wel interessant.
Bmw M20 Engine Overview
Posted by acs3sport - 2008/03/15 19:21
BMW M20 engine.
Successor: BMW M50
Engine: 2.0 L (1990 cc/121 in³)
-------- 2.3 L (2316 cc/141 in³)
-------- 2.5 L (2494 cc/152 in³)
-------- 2.7 L (2693 cc/164 in³)
Similar: Mercedes-Benz M110
The M20 was an I6 piston engine of BMW.
The 12-valve, belt driven SOHC design was introduced in the 1976 BMW 520/6 and 320/6. With displacements ranging
from 2.0 to 2.7 liters, it was the "little brother" to the larger BMW M30 engine.
Powering the E21 and E30 3-Series, as well as E12, E28 and E34 5-Series cars, it was produced in 4 decades, with the
last models of the E30 325i touring built in 1992. At that time, the newer M50 engines with 4 valves and DOHC were
already used in the E36 and E34 for some years.
As BMW M21, it became a Diesel, also available with a turbocharger.
The small 2 Liter engine, the entry-level version to the six cylinder ranges, was very smooth running, but lacked torque
and required higher revs, resulting in higher fuel consumption. It was never imported to North America due to federal
emissions regulations. It used the same cylinder head casting as the 2.3 liter m20 in the e12 and e21 2.3 liter motors and
the pre 1987 2.7 liter eta motors. All of the 2 liter versions were carbureted until the e30 320i, which used Bosch Motronic
version 1.1/1.3 to work with a catalytic convertor.
- 1977–1981 E12 5-series
- 1977–1982 E21 3-Series
- 1982–1987 E28 5-Series
- 1983–1993 E30 3-Series
- 1988–1990 E34 5-series
The 323i began as an E21 model and continued with better fuel injection and several internal revisions in the e30 323i.
The e21 used the same cylinder head casting as the pre-1987 eta cars, only drilled to oil a seven bearing cam. The e30
323 used a specialized head casting with much larger ports. Though it had the same combustion chambers and valves
as the e21 and eta heads, it had much more potential for high rpm power. The e30 323 head can be bolted on to an eta
2.7 liter block in conjunction with other modifications to the intake, exhaust and fuel injection systems to make very good
- 1977–1982 E21 323i
- 1983–1985 E30 323i
The German version of the M20B25 produced 169 HP with a catalytic converter, and 171 without. It featured a 12-valve
SOHC head with larger valves, 84 mm (3.3 in) bore, and 75 mm (3 in) stroke. Most significantly it had redesigned pistons
and combustion chambers for better power, more resistance to detonation and higher thermodynamic efficiency. It was
equipped with Bosch Motronic 1.1/1.3 Adaptive fuel injection. With a minor modification that adjusts the idle speed of a
cold engine, the 325i fulfills Euro 2 emission requirements in Germany, resulting in a lower tax compared to Euro 1 (as of
Bimmerianz - Bimmerianz FireBoard Forum Component version: 1.0.4 Generated: 14 December, 2008, 13:50
- 1986–1994 E30 3-Series
- 1989–1990 E34 5-Series
- 1988–1991 E30 Z1
The 2.7 L M20B27 was designed for efficiency (thus the e for the Greek letter eta in 325e). It had an 84 mm (3.3 in) bore
and with 81 mm (3.2 in) a longer stroke, for a total displacement of 2693 cc. The eta had only four effective camshaft
bearings for reduced internal friction, with all seven cast into the head but only four corresponding journals on the cam.
The heads were drilled to oil accordingly.
Output was between only 121 hp (up to 1987) and 127 hp (after 1987) but fuel efficiency was fairly good for the period
and for that size engine. The low-revving high torque design was resonably well received, but the 325e designation
caused it to be compared to the later 325i which had more power and a more exciting sound with its higher range of revs.
It is interesting to note that the eta and the b25 engine, despite a 47 hp disparity in power output, produce a similar
amount of torque at about 170 ft·lbf at medium revs. In theory, this should have resulted in similar acceleration in top
gear, but due to differences in gearing these were different. The 325/325e(s) used 2.79 and 2.93 rear axle ratios
depending on the model year. The 325i sedan used a 3.64 ratio, and 3.91 in the touring and late ix variant. This equates
to lower torque at the wheels on eta cars and results in substantially milder acceleration.
All eta engines used Bosch Motronic engine management systems that were calibrated for maximum fuel economy. The
result was a very conservative spark advance curve and fuel delivery curve. In addition, the Motronic had a built-in rev
limiter that engaged at around 4700 rpm. This very low redline was the result of the four bearing cam, soft valve springs,
intake manifold design and camshaft design. Considering the very low overlap and short duration the motor didnt make
any real power up high anyway.
For the 1988 model year, the eta cars got a warming over from the factory. This entailed the previously mentioned Bosch
Motronic Fuel Injection, a 325i head with the larger 325i valves, ports and revised combustion chambers, special pistons
to fit the 2.7 liter stroke with the 2.5 liter head, a dual pipe exhaust system and a 5300 RPM rev limit. Though it only
made slightly more power in stock form, it could be easily boosted by bolting on a 325i head with a more aggressive
performance camshaft, a complete 325i intake manifold and throttle and plugging in the 325i engine control unit with a
performance chip. Depending on which cam and chip is used, that motor can make over 200 horsepower.
In aftermarket modifications that are inspired by custom versions of Alpina and AC Schnitzer, the long-stroke eta engine
block is often combined with a 325i head to a so-called 327i that combines the high low-rev torque of the eta with the toprange
power of the 325i.
- 1982–1987 525e (or 528e in the US)