Question: What is the abbreviation of the engine used by the BWW B57?

Context paragraphs:
BMW B57: The BMW B57 engine is a straight-six cylinder turbodiesel engine produced by the automobile manufacturer BMW.  Together with the B37 (three-cylinder diesel engine), the B47 (inline-4 cylinder diesel engine), and the three inline-4 and inline-6 petrol engines (B38 (three-cylinder), B48 (four-cylinder) and B58 (six-cylinder)), the B57 is one of the latest (as of 2017) modular engines from BMW.  The modular motors are used in BMW models as well as in MINI models.  The B57 replaced the N57 diesel engine family in the new 5-series and 7-series.  This new engine is available in configurations with up to 4 turbochargers that operate in a double-series layout.  Output is up to 400 horsepower and 569 lb-ft of torque.

Detroit Diesel Series 51: The Detroit Diesel Series 51 was a two-stroke diesel engine built by General Motors, Detroit Diesel Division from 1951 to 1959.  Unlike other GM/Detroit Diesel engines, the 51 series designation did not refer to the cylinder displacement, but rather to the year it was introduced.  Two versions were produced, an inline two-cylinder (2-51, 108 cid ) and an inline four-cylinder model (4-51, 216 cid ).  This was accomplished by using loop scavenging ports for both intake and exhaust along with a mechanical blower.  This engine used a dry sleeve with 9 intake ports and three exhaust ports in that sleeve.  These sleeves were located in such a way that the exhaust ports lined up with exhaust ports in the block that were physically higher than the intake ports in the block.  This resulted in pressurized cool air being forced through the intake ports just after the exhaust started exiting (note that the exhaust ports in the sleeves were higher at the top than the intake ports while the bottom of all ports in the sleeve are at the same height.  The net compression ratio is 18:1.  Unlike a two cycle gasoline engine, the crankcase was not used to draw in the fuel/air mixture.  Instead, the blower forced air in the intake ports and fuel was injected by a camshaft actuated injector which was pressurized by a gear pump.  As fuel is injected just before top dead center, little unburned fuel is expelled in the exhaust, unlike a two-cycle gasoline engine.  The elimination of exhaust valves reduced the complexity and weight of the engine.  The power output and RPM of this engine was controlled by governing the intake air and controlling the opening of the injectors with shutdown accomplished by completely closing off the air intake.  The much lower weight of this engine compared to engines with valves made it quite suitable for applications where other engines of the same horsepower were not feasible.  Its uses include: Marine propulsion, generators, pumps, air compressors, road graders and other industrial uses.  It was never factory installed for automotive purposes but conversion kits and engines were made available for automotive use.  This engine design did not see widespread use due to not being able to reduce the exhaust noise to an acceptable level, as any exhaust restriction would have resulted in a reduction of power and efficiency.  It was a very fuel efficient engine with a high power output to fuel consumption ratio.

Harley-Davidson Knucklehead engine: The knucklehead is a retronym used by enthusiasts to refer to a Harley-Davidson motorcycle engine, so named because of the distinct shape of the rocker boxes.  The engine is a two-cylinder, 45 degree, pushrod actuated overhead valve V-twin engine with two valves per cylinder.  It was the third basic type of V-Twin engine used by Harley-Davidson, replacing the Flathead-engined VL model in 1936 as HD's top-of-the-line model.  The engine was manufactured until 1947 and was replaced by the Panhead engine in 1948.  The Knucklehead-engined models were originally referred to as "OHVs" by enthusiasts of the time and in Harley's official literature; the nickname arose from the California chopper culture of the late 1960s.

EcoDiesel: EcoDiesel is an engine used in the Ram 1500 since 2014, as well as in the Jeep Grand Cherokee.  Approximately 20% of 2015 RAM 1500s are equipped with the engine, mostly ones sold in Europe.  FCA uses the EcoDiesel name for two different engines.  One is the VM Motori A 630 DOHC 3.0L engine used in the Grand Cherokee, and Ram.  The other is a Fiat 3.0L diesel used in the Ram ProMaster.

River Don Engine: The River Don Engine is a 1905-built steam engine used for hot rolling steel armour plate.  It is a 3-cylinder simple engine of 40 in diameter, 48 in stroke.  At its operating steam pressure of 160psi, it developed 12000 hp , and was able to reverse from full speed in 2 seconds.  The rapid reverse was an essential feature of an engine used for rolling, as delays would result in cooling of the workpiece.  This engine was one of four built to the same design, one going overseas to the Japanese Government, one to John Brown's Atlas plant, and the destination of the final one being William Beardmore of Glasgow.  It is claimed to be one of the most powerful steam engines ever built, and the most powerful remaining in Europe.

BMW B47: BMW B47 is a 2.0 L four-cylinder common rail diesel engine from German car manufacturer BMW.  It debuted in 2014 in the BMW X3 and replaced the previous N47 engine.  Together with the B37 (three-cylinder diesel engine) and the B57 (inline six-cylinder diesel engine) and the three gasoline engines: B38 (three-cylinder), B48 (four-cylinder) and B58 (six-cylinder), the B47 is part of a family of modular engines from BMW introduced in 2013/2014.

Straight-six engine: The straight-six engine or inline-six engine (often abbreviated I6 or L6) is an internal combustion engine with the cylinders mounted in a straight line along the crankcase with all the pistons driving a common crankshaft (straight engine).

Non-road engine: Non-road engine (which may include non-road equipment and non-road vehicle) is an internal combustion engine or a gas turbine engine used for other purposes than being an engine of a vehicle operated on public roadways.  The term is commonly used by regulators to classify the engines in order to control their emission.  Non-road engines are used in an extremely wide range of applications which may include machinery and engines of vehicles in other modes of transportation with different fuel types such as gasoline and diesel fuel.  In many jurisdictions, the term non-road engine is assumed to refer to the engines that have mobility or portability which is separated from the term stationary engine.  The definition of non-road engine may explicitly exclude certain non-road vehicles such as aircraft, locomotives, and ocean-going marine vessels.  In Europe, the regulations are specifically clarified on the mobility by using the term non-road mobile machinery (NRMM).  In Australia, the definition includes some stationary engines such as electric generators and pumps.

Honda Rafaga: The Honda Rafaga series CE4 and CE5 was a compact 4-door sedan sold only in Japan by Honda, introduced in January 1993, and used the same 5-cylinder engine that was used in the Honda Inspire and the Honda Vigor and shared a platform with the second generation CE series Honda Ascot.  "Rafaga" is Spanish for "gust" or "blustery".  The engine is installed longitudinally, the same configuration used in the Vigor and Inspire.  The Rafaga was third in Hondas hierarchy of sedans, and a sister car to the Ascot, which was sold at the "Honda Primo" dealership network.  The Rafaga was sold in Japan at "Honda Verno" dealerships, and was one level up from the Honda Integra.  As with other Honda products, the Rafaga used double wishbone suspension at the front and rear wheels.  The "2.5 S" trim level came with a front suspension upper strut brace in the engine compartment.  In Japan, the smaller G20A engine used regular grade fuel, while the larger G25A engine used premium grade fuel.

HG-3 (rocket engine): The HG-3 was a liquid-fuel cryogenic rocket engine which was designed for use on the upper stages of Saturn rockets in the post-Apollo era.  Designed in the United States by Rocketdyne, the HG-3 was to have burned cryogenic liquid hydrogen and liquid oxygen propellants, with each engine producing 1400.7 kN of thrust during flight.  The engine was designed to produce a specific impulse ("I") of 451 seconds in a vacuum, or 280 seconds at sea level.  Developed from Rocketdyne's J-2 engine used on the S-II and S-IVB stages, the engine was intended to replace the J-2 on the upgraded S-II-2 and S-IVB-2 stages intended for use on the Saturn MLV, Saturn IB-B and Saturn V/4-260 rockets, with a sea-level optimised version, the HG-3-SL, intended for use on the Saturn INT-17.  The engine was cancelled, however, during the post-Apollo drawdown when development of the more advanced Saturn rockets ceased, and never flew, although the engine was later used as the basis for the design of the RS-25 Space Shuttle main engine.

Supporting paragraphs: BMW B57 Straight-six engine
Answer: I6 or L6