Power units of the German concern BMW, which belonged to the S70 series, were characterized by the presence of 12 cylinders. This power unit was based on the M70 motor line. The motor was manufactured for installation on 8 series cars in the E31 body, as well as on the McLaren F1 sports car.
S70B56 is a modification of the S70 series, which provided 5.6 liters of displacement, and was developed specifically for installation on the E31 850 CSi . Cars began to be equipped with it in September 1992. This power unit was based on the outdated M70 engine, which was slightly updated in technical terms. The changes included installation of a new engine management system M1.7 with EML. Also, the motor was characterized by increased performance.
The power unit crankcase was made from an alloy of two metals – aluminum and silicon. Like the M70 engine, the cylinder blocks were positioned at an angle of 60 degrees relative to each other.
The system providing engine management included two DME M1.7 electronic powertrain control units, which operated separately for each row of cylinders, independently of each other. The injection system, power supply and ignition were also controlled by this element. Electronic throttle control was accomplished by the EML. ASC+T was installed as an add-on.
S70B56 engine specifications
| Power, hp. | 380 |
| Fuel type | Premium gasoline AI-98 |
| Volume, cm*3 | 5576 |
| Maximum torque, N*m (kg*m) at rpm. | 550 (56) / 4000 |
| Fuel consumption, l/100 km | 12.8 |
| Engine type | V-twin, 12-cylinder. |
| Cylinder diameter, mm | 86 |
| Number of valves per cylinder | 2 |
| Maximum power, hp (kW) at rpm. | 380 (279) / 5300 |
| Compression ratio | 9.8 |
| Piston stroke, mm | 80 |
Advantages
Increased power and torque is the main goal that guided the engineers of the German concern to design the S70B56 power unit. Utilizing the full potential of the M70 engine was also one of the main objectives of this engine design.
A huge number of improvements and technical modifications allowed to increase the productivity of the power unit by almost 12 percent. The fuel compression ratio in the combustion chamber began to be 9.8, which is quite high even today. The increase in engine power was almost 30 percent, 27 percent to be exact. Torque was increased by 22 percent.
The crankshaft has been forged for maximum strength. The crankshaft has been forged to maximize its life and performance at high speeds, supported by 7 bearings.
The connecting rods, as well as the flywheel, in this engine were used from the base version of the M70 engine. The pistons of this engine were completely redesigned and their design was modified. For the production of pistons used aluminum alloy, which was coated with a special layer of Ferrostan. The piston groups for the two rows of cylinders were different and not interchangeable.
The combustion chamber was characterized by the installation of a cavity at an angle to the spark plugs. Both cylinder heads matched the M70 power unit, which differed by two valves per cylinder. The camshaft drive was also unmodified, so it remained from the base model.
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