Fuel injection at 1600 bar and innovative piezo injectors
Mercedes engineers have refined the common-rail direct injection system, achieving further progress in fuel consumption, exhaust emissions and combustion noise with this third-generation technology. Newly developed piezo injectors operate much more rapidly and precisely than the previous solenoid valves, and ensure a particularly finely metered fuel supply to the cylinders. This allows the fuel injection to be even more precisely adjusted to the current load and engine speed, and now makes five injections per power stroke possible at a peak pressure of up to 1600 bar.
Electrically controlled intake port shut-off modifies the turbulence of the intake air as it enters the cylinders, optimising the combustion process with the aim of further reducing the fuel consumption and exhaust emissions.
The likewise new electronic control unit manages all the engine functions – from the quick-start glow system and automatic start function to control of the high-pressure pump. The VNT turbocharger (Variable Nozzle Turbine) with electrically adjustable turbine blades, exhaust gas recirculation with a control valve and intake air throttling are regulated as the situation requires on the basis of measured data. In addition the microprocessor exchanges data with the seven-speed automatic transmission and the Electronic Stability Program.
Exhaust emissions at EU4 level, particulate filter as standard in Germany
Thanks to this precise engine management system, the nitrogen oxide and particulate emissions of the V6 engine are within the strict limits of the EU4 standard. Two oxidising catalytic converters are responsible for conversion of the carbon monoxide and hydrocarbons: a light-off converter located near the engine and a main converter in an underfloor location.
To reduce soot emissions even further, Mercedes Benz offers a maintenance-free particulate filter system which is offered as an option in the UK. The filter is purged without the use of additives by selective adjustment of different engine functions. Depending on the operating parameters and filter condition, the variable third-generation common-rail technology allows up to two precisely coordinated post-injections with the aim of specifically increasing the exhaust temperature. This means that the particulates trapped in the filter are burned off in a controlled manner.Published 18 December 2004