CDI technology development
Mercedes engineers have perfected the common rail technology by using an innovative inlet metered high-pressure injection pump and seven-hole injectors.

The fuel is distributed by two separate rails which are controlled by a function module centrally located between the two cylinder banks. A sensor monitors the injection pressure, enabling the microcomputer of the V8 engine to compare these data with the stored parameters and adapt the fuel injection as required.

As on all Mercedes-Benz CDI engines, the innovative pilot injection also optimizes the combustion process on the new S400 CDI and ensures exemplary low noise levels.

Electrically controlled turbochargers
The two turbochargers - one for each cylinder bank - are coupled to a water-cooled intercooler and play a key role in the CDI V8’s impressive torque and power development.

Thanks to electronic control by dual mass air flow sensors, the bi-turbo system operates synchronously and precisely adapts the extra supply of combustion air to the actual power requirement.

The same purpose is served by the variable nozzle turbines with electric adjustment of the guide vanes.

Aluminium heads and crankcase
Thanks to an uncompromising lightweight construction, the new V8 diesel engine is the lightest power plant of its displacement and cylinder category.

Apart from the two cylinder heads, Mercedes-Benz now also makes the entire crankcase from aluminium. The new V8 engine weighs in at just 245 kg.

Mercedes engineers have also adapted the standard five-speed automatic transmission of the new S400 CDI to the performance characteristics of the eight-cylinder engine to provide optimum driveaway dynamics. A newly developed converter ensures that after moving off from standstill the sedan quickly reaches an advantageous rev range, allowing the engine to unleash its mighty pulling power. Around 400 Newton metres of torque are on tap from just 1200 rpm.