|BMW M70 engine|
|Displacement||5.0 L (305 cu in)|
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 (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.
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 1.7 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.
|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
|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
|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
|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
- S70/3 specifications are for the race car with twin 32.9 MM air restrictors, as required by 24 Hours of Le Mans rules at the time.
|BMW S70 engine|
Engine bay of a McLaren F1
|Displacement||5.6–6.1 L (342–372 cu in)|
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. With 1,510 units produced, this is the lowest production BMW engine to date.
- 1992–1996 E31 850CSi
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, and thus featuring 4 valves per cylinder and variable valve timing (called dual-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 (584 lb).
- 1993–1998 McLaren F1
The S70/3 is a racing engine based on the S70/2.
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