BMW S70B56
| BMW M70 engine | |
|---|---|
 |
|
| Overview | |
| Manufacturer | BMW |
| Production | 1987–1996 |
| Combustion chamber | |
| Configuration | SOHC 60° V12 |
| Chronology | |
| Predecessor | None |
| Successor | BMW M73 |
| BMW S70/2 engine | |
|---|---|
 |
|
| Overview | |
| Manufacturer | BMW |
| Production | 1993–1998 |
| Combustion chamber | |
| Configuration | DOHC 60° V12 |
| Chronology | |
| Predecessor | None |
| Successor | None |
The BMW M70 is a V12 SOHC petrol engine, 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 V12 DOHC petrol engine, which powered the 1993 to 1998 McLaren F1.
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: SOHC valvetrain, 91 mm (3.6 in) bore spacing, 84 mm (3.3 in) bore, 75 mm (3.0 in) stroke and 8.8:1 compression ratio.
The M70 has the following differences with the M20 engine:
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.
Applications:
The first engine to use the S70 name is a 5,576 cc (340 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.
Three prototype DOHC S70 engines with four valves per cylinder were constructed, prior to the decision to not produce an E31 M8 model.
Applications:
The S70/2, while sharing the same 12 cylinder layout and design principle as the S70B56, is essentially two European market S50s joined together, and thus features 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).
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