In March 1991 the new S-Class generation (designated internally as the 140 series) made its debut at the Geneva Motor Show. The production of the 6.0-litre V12 engine model began in February 1992, one year after main production start-up for the 140 series.
The 6.0-litre V12 M 120 engine was an entirely new design. Not only was it the first twelve-cylinder Mercedes-Benz made for a production passenger car, but it was also the most powerful Mercedes-Benz car engine of its day, with a rated power output of 300 kW (408 hp). With a peak torque of 580 Newton metres, it reached the 500 Newton metres mark at 1600 rpm.
As with the six-cylinder and the two V8 engines, the twelve-cylinder was also equipped with four-valve technology, variable intake camshaft and an electronic injection system with hot-wire air mass sensor. With all engines a high priority was placed on minimising exhaust emissions and reducing fuel consumption.
The new fully electronic ignition system calculated the optimum ignition point from 300 ignition maps, tuned for each cylinder individually and to the knock limit in each case. The M 120 was the only twelve-cylinder engine in the world to feature this cylinder-selective anti-knock control.
Without this it would not have been possible to achieve the high compression ratio of 10:1, necessary for optimum use of fuel.
The engine management and drive management were also completely new. All their control modules communicated with one another via a common data channel, meaning the control units could all be active at the same time. This was used for rapidly warming up the catalytic converters when cold-starting the engine, as well as for acceleration skid control and for the new engine friction torque control, which maintained handling stability during power-off situations on slippery road surfaces.
The V12 offered the world’s largest catalytic converter unit for passenger cars. Its seven-litre volume avoided any excess fuel consumption on account of the catalytic converter and ensured a high degree of long-term stability.
Thanks to an innovative concept involving a double-walled and triple-insulated exhaust manifold, as well as double-walled pipes, the ceramic catalytic converters – embedded in insulating expandable matting – reached the optimum operating temperature in a very short time.
8,573 6.0-litre V12 M120 engines where build in Baureihe W140.
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