How BMW got into the 12-cylinder game with the M70 V12 back in the 1980s.
While we at DSF.my believe the internal combustion engine will continue to be a very important aspect of motoring for decades to come, it’s clear to us that its heyday is in the past. Today, many of the premium European brands that once led its development have ceased investing in its further improvement. We thought we’d take this opportunity to look back at one of the legendary ICE units from BMW – the M70 V12.
This year marks the 20th anniversary of BMW Group’s ownership of the Rolls Royce Motor Cars division. Today, Rolls Royce is the primary user of BMW’s current V12 engine, the N74. This engine can trace its lineage back to the original BMW V12, the M70. And no, we’re not talking about their electric 7 Series Flagship when we say M70.
While most would assume that BMW just took an existing M20 inline-6 cylinder design and make a V12 out of it, that is only half the story of the M70. BMW also had an M40 inline-4 cylinder design that was more compact, lighter, and quieter. Using some M40 parts would also help BMW bring the engine to market sooner and at a lower cost. So it took some M40 parts and tooling for the connecting rods, valves, rocker arms. The pistons have a similar design but with offset gudgeon pins and a different material composition.
Meanwhile, the rest of the M70 still isn’t quite the M20 clone as you’d expect. BMW did not use an iron block for the M70 but rather an ‘Alusil’ aluminium-silicon alloy material. It also used mass air flow sensors instead of air flow meters, an electronic throttle control instead of a mechanical throttle cable, a timing chain instead of a timing belt and hydraulic valve lifters instead of mechanically adjusted tappets. All of this reduced servicing requirements for the M70 V12.
BMW also designed the M70 V12 with redundancy in mind. There were two Bosch Motronic 1.7 ECUs, two fuel pumps, fuel rails, distributors, mass airflow sensors, crankshaft position sensors, coolant temperature sensors, and throttle bodies. This meant that if one bank of the engine failed, the M70 would still be able to crank out 150hp and keep the car going.
The M70 debuted in 1987 on the BMW 750iL and later came to a short wheelbase 750i as well as the first BMW 8 Series in the form of the 850i. While the 7 Series models came with a 4-speed automatic, the 8 Series had the option of a six-speed manual.
While it’s questionable if BMW set the gold standard for V12s at the time, they certainly made an engine with a lot of power. With a 5.0L displacement, the M70 had an output of 295hp and 450Nm of torque while the Mercedes-Benz equivalent 5.5L V8 only put out 227hp and 389Nm of torque in the 560 SEL at the time.
You can read more about the M70 V12 engine on BMW Blog.
