The BMW M70 is a naturally-aspirated,

SOHC An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion cha ...

V12 V12 or V-12 may refer to: Aircraft * Mil V-12, a Soviet heavy lift helicopter * Pilatus OV-12, a planned American military utility aircraft * Rockwell XFV-12, an American experimental aircraft project * Škoda-Kauba V12, a Czechoslovak experim ...

petrol engine A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ''E ...

, which was BMW's first production V12 and was produced from 1987 to 1996. The BMW S70/2 engine, largely unrelated to the M70 and S70B56 engines, is a naturally-aspirated,

DOHC An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion c ...

, V12 petrol engine, which powered the 1993 to 1998

McLaren F1 The McLaren F1 is a sports car designed and manufactured by British automobile manufacturer McLaren Cars, and powered by the BMW S70/2 V12 engine. The original concept was conceived by Gordon Murray. Murray was able to convince Ron Dennis to b ...

Design

The M70's design is similar to that of two 2.5 L M20 straight-six engines joined at a 60 degree angle, due to the following features:

single overhead camshaft An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion cha ...

valvetrain, bore spacing of , bore of ,

stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...

of , and a

compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...

of 8.8:1. The M70 has the following differences with the M20 engine: * Aluminium alloy engine block (

AluSil Alusil as a hypereutectic aluminium-silicon alloy (EN AC-AlSi17Cu4Mg / EN AC-48100 or A390) contains approximately 78% aluminium and 17% silicon. This alloy was theoretically conceived in 1927 by Schweizer & Fehrenbach, of the Badener Metall-Ware ...

) instead of cast-iron (both engines have an aluminium

cylinder head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...

), to reduce weight. * Airflow measurement using Mass air flow sensors (MAFs) instead of

Air flow meter An air flow meter is a device that measures air flow, i.e. how much air is flowing through a tube. It does not measure the volume of the air passing through the tube, it measures the mass of air flowing through the device per unit time. Thus ai ...

s (AFMs) to improve fuel economy. *

Electronic Throttle Control Electronic throttle control (ETC) is an automobile technology which electronically "connects" the accelerator pedal to the throttle, replacing a mechanical linkage. A typical ETC system consists of three major components: (i) an accelerator ped ...

instead of a mechanical throttle cable. * A

timing chain In a piston engine, either a timing belt (also called a ''cambelt'') or timing chain or set of timing gears is used to synchronize the rotation of the crankshaft and the camshaft. This synchronisation ensures that the engine's valves open and cl ...

was used instead of a timing belt, to reduce servicing requirements. * Hydraulic valve lifters instead of mechanically adjusted tappets, to reduce servicing requirements. The M70 has two Motronic 1.7 ECUs (one for each cylinder bank). To provide redundancy, the M70 also has two fuel pumps, fuel rails, distributors, mass air flow sensors, crankshaft position sensors, coolant temperature sensors and throttle bodies. Some M70 engines (such as fitted to the E32 750iL Highline) are fitted with two alternators. The second alternator is smaller and is used to charge an auxiliary battery and power equipment in the rear passenger compartment, such as a telephone, fax machine, wine cooler, independent climate control and power sun shields.

Versions

M70B50

Applications: *1987–1994 E32 750i/750iL – this was mated primarily to an automatic

ZF 4HP24 transmission The ZF 4HP24 is a four-speed automatic transmission for passenger cars from ZF Friedrichshafen AG. Introduced in 1987, it was used in a variety of cars from Audi, BMW, Jaguar, and Land Rover. Applications 4HP24 *1986–1994 BMW E32 750i M7 ...

*1989–1994 E31 850i/850Ci – this was mated to either the automatic

or the optional Getrag 560G

S70 engine

S70B56

The first engine to use the S70 name is a variant of the M70 engine fitted only to the E31 850CSi. With 1,510 units produced, this is the lowest production BMW engine to date. Three prototype

dual overhead camshaft An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion cha ...

S70 engines were constructed, prior to the decision to not produce an E31 M8 model. Applications: * 1992–1996 E31 850CSi * 2011 Simbol Design Lavazza GTX-R (twin-turbo version)

S70/2

The S70/2, while sharing the same 12 cylinder layout, bore spacing and design principle as the S70B56, is essentially a new design with the heads based on the European market S50B32, and thus featuring 4 valves per cylinder and

variable valve timing In internal combustion engines, variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with varia ...

(called

VANOS VANOS is a variable valve timing system used by BMW on various automotive petrol engines since 1992. The name is an abbreviation of the German words for ''variable camshaft timing'' (german: variable Nockenwellensteuerung). The initial version ...

by BMW) and individual throttle bodies. A

dry sump A dry-sump system is a method to manage the lubricating motor oil in four-stroke and large two-stroke piston driven internal combustion engines. The dry-sump system uses two or more oil pumps and a separate oil reservoir, as opposed to a conve ...

oiling system is used. The weight of the S70/2, plus ancillaries and full exhaust, is . Applications: * 1993–1998

S70/3

The S70/3 is a racing engine based on the S70/2. Applications * 1998–1999 BMW V12 LM racing car * 1999–2000

BMW V12 LMR The BMW V12 LMR is a Le Mans Prototype built for sports car racing from 1999 to 2000. The car was built through an alliance between BMW Motorsport and Williams F1, and was the successor to the failed BMW V12 LM of 1998. It is famous for earnin ...

racing car * 2000 BMW X5 LM racing car

References

{{BMW automotive petrol engines: 1960s to 1980s M70 V12 engines Gasoline engines by model