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The BMW M21 is a straight-six diesel engine developed by the German engine manufacturer BMW. It has swirl chamber injection and is based on the M20 petrol engine [1] and was produced for BMW by the Upper Austrian Steyr engine plant from 1983 to 1991. It was succeeded by the M51. [2]
Der BMW M21 ist ein Sechszylinder-Reihen-Dieselmotor des bayerischen Motorenherstellers BMW. Der Motor mit Wirbelkammereinspritzung wurde aus dem Ottomotor M20 entwickelt und ab März 1983 im oberösterreichischen Steyr in Serie für BMW produziert. Die Ablösung erfolgte ab 1991 durch den Nachfolgemotor M51. Insgesamt wurden 174.407 Einheiten ...
The BMW M51 is an inline-6 cylinder Diesel engine produced by the Upper Austrian BMW plant in Steyr from July 1991 through February 2000. Its predecessor is the BMW M21, the successor is the BMW M57.
The BMW M21 is a straight-six diesel engine developed by the Bavarian engine manufacturer BMW. It has swirl chamber injection and is based on the M20 petrol engine [1] and was produced for BMW by the Upper Austrian Steyr engine plant from 1983 to 1991. It was succeeded by the M51.
- Sump
- Block
- Head
- Ancillaries
- Fuel
- Oil
- Cooling
The lowest part of the M21 engine is the Sump, an aluminium dish that provides an oil bath for the crankshaft, as well as feeding the oil pump. Oil is drained through a single bolt, Almost all M21 sumps are interchangeable between engines, except for that fitted to the 325iX. Removing the sump on an M21 in situis one of the most irksome chores on t...
The M21 block is a cast iron design with six cylinders. All M21 blocks have an 80mm bore, just like the M20B20petrol engine.
A single head design was used for both turbo and non-turbo versions of the M21. This aluminium core featured a design very similar to the M20 unit. It is not uncommon for these heads to develop cracks between the valve ports, although this does not render the head useless. Modern welding techniques mean that the head can be repaired if necessary, a...
Turbo
Main article: Forced Induction Only one E30 model was fitted with a turbocharger; the 324td. However, identical components were used on the E28524td. The turbo is a standard forced-induction unit, whereby exhaust gases are used to drive a turbine, whose subsequent spinning forces more air through the Intakeside of the engine. This increase in air flow allows more fuel to be added, thus providing more power. The turbo itself was a variant of the standard T3 design including an internal wastega...
EGR
The Exhaust Gas Recirculation valve, or EGR, is a polution control device. Its purpose is to scavenge a portion of the exhaustgases and return them to the cylinders for re-use. The EGR is sits right underneath the turbo, on the manifold. It has a pipe that runs from there to the intake pipe. Also from the EGR is a vacuum tube that runs to something called the aneroid diaphragm, which is right behind the driver's side struttower. From there the pipework goes to a solenoid on the firewall, and...
Flywheel
The M21 flywheel, like all flywheels, keeps the engine spinning long after you take your foot off the throttle. It is also the flat surface to which the clutch mates, ultimately transferring power from the engine to the Drivetrain. The edge of the flywheel is toothed. Known as the ring gear, it is what allows the starter motor to bite onto the engine to start it. The flywheel bots to a pulley at the end of the crank. Two weights of flywheel were fitted to M21 engines. The standard single mass...
Main article: Diesel Unlike all the petrol engines fitted to the E30, the M21 has an exclusive system that cannot be covered in the normal fuel section of this Wiki. However, a number of components are shared; the system still revolves around pressurised fuel, collected from a tank and delivered to injectors by way of a pump. It is only the technic...
Main article: Oil The system is lubricated by a pressurised oil system that oils each moving part of the engine. The oil is circulated from top to bottom and around, and the pressure monitored to ensure that no leaks occur. The driver is notified of this by a warning light of the dash cluster.
Main article: Cooling The M21 block is filled with channels for a liquid coolant. These channels are known as the water jacket, and are designed to allow coolant to flow from the the bottom to the top of the engine and out. Pressurised by a water pump, the coolant flows out to the radiator where it is cooled by air flow through the grille. In the c...
- 87-93
- 42.4
- 62.4
- 3.13
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.
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What engine does a BMW M20 use?
In 1983, BMW introduced its first diesel engine, the BMW M21. The first all-wheel drive BMW was the E30 3 Series 325iX model, which began production in 1985. The E30 became BMW's first model produced in a station wagon (estate) body style, when the "Touring" model was introduced in 1987.
