May 23, 2005 New Mercedes Diesel V8 Delivers More Power with Fewer Emissions and Comparable Fuel Consumption
DaimlerChrysler continues down its diesel engine development path of delivering more power and torque with equivalent or slightly reduced fuel consumption and lower emissions with the introduction of its newest 4-liter V8. The new engine enters production this fall in the new E420 CDI.
The 231-kW (314-hp) V8 develops maximum torque of 730 Nm (538 lb-ft) at engine speeds as low as 2200 rpm. This allows the new E420 CDI to accelerate from 0 to 100 km/h in just 6.1 seconds on its way to a top speed of 250 km/h (155 mph). Combined fuel consumption stands at 9.3 litres per 100 kilometers, equivalent to 25.3 mpg.
Compared to its predecessor V8, the new engine delivers 20% more output, 30% more torque, burns 1% less fuel and meets the Euro4 emissions requirements. The new E420 CDI is fitted as standard with a maintenance-free particulate filter system and two oxidizing catalytic converters, allowing it to keep below Euro4 limits. V8 Mercedes Diesels E 400 CDI E 420 CDI % =CE=94 Introduced 2003 2005 Displacement (cc) 3,996 3,996 0 Power 191 kW (260 hp) 231 kW (314 hp) +21% Torque 560 Nm (413 lb-ft) 730 Nm (538 lb-ft) +30% Acceleration 0-100km/h 6.9 sec 6.1 sec -12% Fuel consumption 9.4 l/100km 9.3 l/100km -1% Mileage 25.0 mpg (US) 25.3 mpg (US) +1% Emissions Euro3 Euro4
The injection system on the V8 is similar to that of the new V6 series introduced last year (earlier post): a 1,600 bar common rail injection system with piezo ceramic injectors that allows particularly precise fuel metering, thus reducing both fuel consumption and exhaust emissions.
A dual pilot injection system acts in just a few milliseconds and significantly reduces the combustion noise generated by the eight-cylinder engine. Added to which, double fuel post-injection helps to clean the residue away from the standard-fitted diesel particulate filter. Merc_v8_turbochargers
Two exhaust-gas turbochargers (pictured at right) are located on the outer sides of the cylinder banks. Integrated hot-film air mass sensors supply the electronics with important basic information for the engine management. Hollow inserts integrated into the intake lines increase the volume of the air before it enters the turbochargers, raising torque output at lower engine speeds by up to 15%.
The V8 engineers used sophisticated airflow calculations and simulations to reduce the loss of pressure typically experienced in the charge air manifolds of turbochargers and provide a sustained improvement in the supply of air to the new diesel engine. Under full load, the pressure loss is some 30% lower in the charge air manifolds at the entry to the turbochargers than in Mercedes-Benz=E2=80=99 previous eight-cylinder CDI engine, and as much as 60% in the charge air manifolds at the exit of the turbochargers. This means that an up to
15% greater air mass can flow through the manifolds.The VNT (Variable Nozzle Turbine) uses new vane geometry for the compressor and turbine wheels and the guide vanes,and the maximum turbocharger speed has been increased, making the new engine more efficient than its predecessor.
A newly developed electronic control unit manages fuel injection, the turbochargers, exhaust gas recirculation and virtually all the other engine functions. The ECU is linked with the other onboard microcomputers via CAN (Controller Area Network) data bus.
A major feature of this digital network is the torque harmonization interface. This is where the data transfer takes place between the engine and the Electronic Stability Program, which ensures that the eight-cylinder powerplant reduces torque when moving off on slippery ground or if the vehicle is in danger of skidding.
A separate data bus links the engine management system with the generator and glow plug control device=E2=80=94the cornerstone of a newly developed quick-start glow system. This shortens the duration of the diesel engine=E2=80=99s preglow phase, putting the compression ignition engine on a par with its petrol-driven counterparts in this respect as well.
The combination of design refinements and increased intelligence in the ECU results in the power and emissions improvements.
Now if DaimlerChrysler would only begin to apply these enhancements to smaller engines to deliver not just more powerful cars with comparable fuel efficiency, but more fuel efficient cars with comparable power.