BMW M70

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 91 mm, bore of 84 mm, stroke of 75 mm, and a compression ratio 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), to reduce weight.
• Airflow measurement using Mass air flow sensors (MAFs) 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, to reduce servicing requirements.
• Hydraulic valve lifters instead of mechanically adjusted tappets, to reduce servicing requirements.

The M70 has two Motronic 1.3 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
• 1989–1994 E31 850i/850Ci – this was mated to either the automatic ZF 4HP24 transmission or the optional Getrag 560G
• 1988 Alpina B12
• 1991 BMW Nazca M12
• 1992 BMW Nazca C2

S70 engine {{Anchor|S70}}

6064 cc 5990 cc 87 mm 85.9 mm

S70B56

The first engine to use the S70 name is a 5576 cc variant of the M70 engine fitted only to the E31 850CSi. With 1,510 units produced, this is the lowest production number BMW-engine, for a BMW-car 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
• 1993 BMW Nazca C2 Spider
• 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 S50B30, and thus featuring 4 valves per cylinder and variable valve timing (called VANOS 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 265 kg.

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 concept car

References

References

1. "BMW E32 parts".
2. (5 June 2014). "The 8-Series Was One Of BMW's Best Failed Experiments".
3. "1989 BMW 750i E32 Specification".
4. "BMW M70, M72 and M73 V12 Engines".
5. "7' E32 750iL Mass air flow sensor".
6. "7' E32 750iL Timing and valve train-timing chain".
7. "BMW".
8. "V12 (M70) Regular Maintenance".
9. (5 February 2016). "Engines Exposed: Just How Far Has BMW's Beastly V12 Come?".
10. "BMW M70B50 V12-Zylinder-Ottomotor".
11. "Diamètre des brides / Air rectrictors [sic] diameter".
12. (2 June 2017). "McLaren F1 GTR Longtail stretches its legs at Spa-Francorchamps".
13. (18 April 2016). "1997 McLaren F1 GTR Long Tail | McLaren".
14. "Rare race spec McLaren F1 GTR Long tail found on sale".
15. (2020-06-18). "Street-Legal McLaren F1 GTR Longtail Has Rich History, $15 Million Asking Price". Carscoops.
16. "Engine specifications for Motorsport engines".
17. "Worldwide Shipments: S70 850CSi 1992–1996".
18. "BMW S70 and S70/2 V12 Engines".
19. "BMW Classic – Recherche-Client".
20. (14 December 2014). "1994 McLaren F1: First Drive Flashback".
21. "F1 – McLaren's Road Car An Autocar & Motor Book".
22. Radu, Vlad. (2022-05-27). "The McLaren F1's S70/2 V12 Was BMW M’s Greatest Gift to the Automotive World".
23. "BMW Shows the X5 Le Mans Concept and Its V12 Engine with 700+ HP".
24. (16 June 2020). "2001 BMW X5 Le Mans Concept Had the V-12 Heart of a McLaren F1".
25. "The BMW X5 Le Mans".