BMW M70

The BMW M70 is a SOHC V12 petrol engine, which was BMW's first production V12[1] and was produced from 1987 to 1996.

BMW M70 engine
Overview
Production	1987–1994
Layout
Configuration	60° V12
Displacement	5.0 L (305 cu in)
Block material	Aluminium
Head material	Aluminium
Valvetrain	SOHC
Combustion
Fuel type	Petrol
Chronology
Predecessor	None
Successor	BMW M73

The BMW S70/2 engine, largely unrelated to the M70 and S70B56 engines, is a 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,[2] due to the following features: single overhead camshaft valvetrain, bore spacing of 91 mm (3.6 in), bore of 84 mm (3.31 in), stroke of 75 mm (2.95 in), and a compression ratio of 8.8:1.[3]

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), to reduce weight.[4]
• Airflow measurement using Mass air flow sensors (MAFs)[5] instead of Air flow meters (AFMs) to improve fuel economy.
• Electronic Throttle Control instead of a mechanical throttle cable.
• A timing chain was used instead of a timing belt,[6] to reduce servicing requirements.
• Hydraulic valve lifters instead of mechanically adjusted tappets, to reduce servicing requirements.

The M70 has two Motronic 1.7[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.[8]

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.[9]

Versions

Version	Displacement	Power	Torque	Redline	Years
M70B50	4,988 cc (304.4 cu in)	220 kW (295 hp) at 5,200 rpm	450 N⋅m (332 lb⋅ft) at 4,100 rpm	6,000	1987-1994
S70B56	5,576 cc (340.3 cu in)	280 kW (375 hp) at 5,300 rpm	550 N⋅m (406 lb⋅ft) at 4,000 rpm	6,400	1992-1996
S70/2	6,064 cc (370.0 cu in)	461 kW (618 hp) at 7,400 rpm	650 N⋅m (479 lb⋅ft) at 6,700 rpm	7,500	1993-1998
S70/3	5,990 cc (365.5 cu in)	427 kW (573 hp) at 6,500 rpm	670 N⋅m (494 lb⋅ft) at 4,500 rpm	8,000	1998-2000

• S70/3 specifications are for the race car with twin 32.9 MM air restrictors,[10] as required by 24 Hours of Le Mans rules at the time.[11]

M70B50

Applications:

• 1987–1994 E32 750i/750iL - this was mated exclusively 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

BMW S70 engine
Engine bay of a McLaren F1
Overview
Production	1992–2000
Layout
Configuration	60° V12
Displacement	5.6–6.1 L (342–372 cu in)
Block material	Aluminium
Head material	Aluminium
Valvetrain	DOHC
Combustion
Fuel type	Petrol
Chronology
Predecessor	None
Successor	None

S70B56

The first engine to use the S70 name is a 5,576 cc (340.3 cu in) variant of the M70 engine fitted only to the E31 850CSi.[12] With 1,510 units produced, this is the lowest production BMW engine to date.[13]

Three prototype dual overhead camshaft S70 engines were constructed, prior to the decision to not produce an E31 M8 model.[14]

Applications:

• 1992–1996 E31 850CSi

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 S50,[15] and thus featuring 4 valves per cylinder and variable valve timing (called double-VANOS by BMW) and individual throttle bodies. A dry sump oiling system is used. [16] The weight of the S70/2, plus ancillaries and full exhaust, is 265 kg (584 lb).[17]

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 racing car
• 2000 BMW X5 LM racing car

References

1. "BMW E32 parts". www.usautoparts.net. Archived from the original on 3 July 2013. Retrieved 4 August 2017.
2. "The 8-Series Was One Of BMW's Best Failed Experiments". www.jalopnik.com. Retrieved 30 July 2017.
3. "1989 BMW 750i E32 Specification". www.carfolio.com. Retrieved 4 August 2017.
4. "BMW M70, M72 and M73 V12 Engines". www.unixnerd.demon.co.uk. Retrieved 4 August 2017.
5. "7' E32 750iL Mass air flow sensor". www.realoem.com. Retrieved 30 July 2017.
6. "7' E32 750iL Timing and valve train-timing chain". www.realoem.com. Retrieved 30 July 2017.
7. "BMW" (PDF). Retrieved 1 February 2019.
8. "V12 (M70) Regular Maintenance". www.bmwe32.masscom.net. Retrieved 4 August 2017.
9. "Engines Exposed: Just How Far Has BMW's Beastly V12 Come?". www.carbuzz.com. Retrieved 30 July 2017.
10. "Le Mans '99". bmw-grouparchiv.de. Retrieved 9 June 2019.
11. "Diamètre des brides / Air rectrictors diameter" (PDF). lemans-history.com. Retrieved 9 June 2019.
12. "Engine specifications for Motorsport engines". www.bmwheaven.com. Retrieved 4 August 2017.
13. "Worldwide Shipments: S70 850CSi 1992-1996". www.8coupe.com. Retrieved 4 August 2017.
14. "BMW S70 and S70/2 V12 Engines". www.unixnerd.demon.co.uk. Retrieved 4 August 2017.
15. "BMW Classic - Recherche-Client". bmw-grouparchiv.de. Retrieved 28 February 2018.
16. "1994 McLaren F1: First Drive Flashback". Road & Track. Retrieved 4 May 2017.
17. "F1 – McLaren's Road Car An Autocar & Motor Book". www.audiosignal.co.uk. Retrieved 4 August 2017.