BMW S70

BMW M70 engine
Overview
Manufacturer	BMW
Production	1987–1996
Combustion chamber
Configuration	60° V12
Chronology
Predecessor	None
Successor	BMW M73

The BMW M70 is a V12 SOHC piston engine which was BMW's first production V12 and was produced from 1987 to 1996.

The M70 was not directly derived from two M20 straight-6 engines joined at a 60 degree angle as is often thought, but was designed in conjunction with the similar 4 cylinder M40, and thus share many design elements with the earlier BMW SOHC engines. Both units were machined on the same tools with many common parts. The engine has the same 84mm bore and bore spacing as the M40, but with the 75mm crankshaft stroke and six cylinder bank(s) of the 2.5 litre M20. The M70 has two Motronic 1.7 ECUs (one for each cylinder bank).

This said, the M70 engine does differ from the M40 engine in a number of key ways, including:

Some examples of this engine are fitted with two alternators, such as in the E32 750iL Highline. One alternator is a full sized unit to service the car as on "regular" V12 models (regular to be taken in context of course), while the secondary smaller unit is used to charge an auxiliary battery and power all options in the rear passenger compartment, such as telephones and fax machines, as well as the wine cooler, independent climate control and power sun shields.

The compression ratio is 8.8:1, stroke is 75 mm (3.0 in) and bore is 84 mm (3.3 in).

Applications:

This 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.

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). Unlike the M70, it does not have hydraulic valve lifters, and as such requires routine valve adjustment.

Applications:

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