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 % Δ
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
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
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’ 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—the cornerstone of a newly
developed quick-start glow system. This shortens the duration of the
diesel engine’s preglow phase, putting the compression ignition
engine on a par with its petrol-driven counterparts in this respect as
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.