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, V12 petrol engine, which powered the 1993 to 1998
McLaren F1.
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 valvetrain, bore spacing of ,
bore
Bore or Bores often refer to:
*Boredom
* Drill
Relating to holes
* Boring (manufacturing), a machining process that enlarges a hole
** Bore (engine), the diameter of a cylinder in a piston engine or a steam locomotive
** Bore (wind instruments), ...
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) 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 instead of a mechanical throttle cable.
* A
timing chain 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 (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
*1989–1994
E31 850i/850Ci – this was mated to either the automatic
ZF 4HP24 transmission 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 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 oiling system is used. The weight of the S70/2, plus ancillaries and full exhaust, is .
Applications:
* 1993–1998
McLaren F1
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