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 DaimlerChrysler South Africa's
Mercedes-Benz passenger car division is venturing into bold territory by
introducing this markets first diesel-powered super-saloon. The S320CDI has all the bells and
whistles of its petrol-powered stable-mates, but beats cars half its price
and size in the economy stakes. Witch this space as others are bound to
folow.
Now that diesel fuel with a lower sulphur content is available in SA, Merc
feels comfortable to introduce its flagship car in diesel form. However,
DCSA makes no bones about the fact that SA needs to bring the sulphur content
of our diesel down to European levels to facilitate significantly
reduced engine wear and oil breakdown, and in turn increased
engine life and service intervals.
The S320CDI is fitted with a modern 6-cylinder direct-injection diesel engine
with VNT (variable nozzle turbine) turbocharger and four valves per
cylinder. Peak power delivery is 145 kW, while maximum torque is a
gut-wrenching 470 Newton-meters from 1 800 r/min. According to DCSA, this
3,2-litre engine has the highest torque rating in its displacement class.
Performance figures include a 0 - 100 km/h sprint time of 8,8 seconds and
a top speed of 230 km/h. However, it is in the economy stakes that it
shines: claimed figures are 8 litres/100 km, allowing around 1100 km of
travel on one 88 litre tankful - phenomenal for a car of this size and
weight.
The secret is in the direct injection engine based on the common rail
principle, and with the modern configuration of four valves per cylinder.
The single shared fuel line ("common rail") upstream of the cylinders of
CDI engines serves as an accumulator and distributes the fuel at constant
pressure to the injectors. Here, powerful solenoid valves adjust the start
of injection and the fuel quantity for each combustion chamber
individually, as a function of actual need, in response to the control
signals from the electronic engine management system. All relevant
environmental parameters are detected and utilized to control the
injection and other engine processes. In other words, pressure generation
and fuel injection occur independently of each other.
The pilot injection of the CDI diesel engines can be flexibly adapted to
meet actual requirements. With the aid of pilot injection, Mercedes
engineers have been able to compensate for the disadvantages inherent to
the direct injection principle, such as high noise level compared to
pre-chamber engines and the higher nitrogen oxide emissions due to the
rapid rise in temperature in the cylinders.
 With pilot injection, a small quantity of diesel fuel is released into the
cylinders a few milliseconds before the main injection. This pilot
quantity ignites, thereby preheating the combustion chambers. This process
improves the conditions for the main injection, by ensuring that the fuel
is ignited more rapidly, with the result that pressure and temperature no
longer rise abruptly. Thanks to pilot injection, the noise level of modern
CDI engines is much lower than for earlier pre-chamber engines.
An important criterion favouring common rail technology, according to DCSA,
is the durability of the engines. One of the drawbacks inherent to the
operating principle of conventional injection systems, which always only
build up their injection pressure for a short period, is that a constant
succession of high forces are applied to the control drive and generate
high loads. It has to withstand peak loads of up to 180 Newton-meters,
which in the view of Mercedes engineers cannot be guaranteed for the long
term.
In terms of features, the S320CDI is equipped identically to the S320
petrol model. This includes the COMAND system, Distronic, Keyless Go, and
dynamic multi-contour seat backs for the driver and front passenger that
are amongst a comprehensive range of optional equipment available to the
S320CDI. Standard innovations include Linguatronic (voice control system)
and xenon headlights with headlamp cleaning system. The entire car
incorporates more than 30 innovations that have given rise to more than
340 patent applications from Daimler engineers.
The optional Keyless Go allows entry and operation without the use of a
conventional key. This works by way of a handy chip card carried in a
shirt or jacket pocket. To enter the car, the driver simply has to touch a
door handle. In response, the "Keyless Go" system carries out a
split-second data exchange with the vehicle by induction and radio signal
in order to identify the driver. The door is then unlocked. Again, no key
is required to start the engine: the driver simply presses a button on the
selector lever.
Operation of the navigation system, car, radio, telephone, CD changer and
TV receiver has been made clearer and more convenient by the new Cockpit
Management and Data System (COMAND) which is installed in the centre
console of the S320CDI and keeps the driver informed via a large colour
display.
DISTRONIC  combines the cruise control function with a radar sensor in the
radiator grille to scan the road ahead of the S-Class over a distance of
up to 150 meters. It automatically maintains a safe following distance
from traffic in front of the car by automatically easing up on the
throttle and even activating the brakes if necessary. However, if the
situation is too hazardous to allow the car to be braked solely by
computer, an audible alarm signal is sounded and a red warning triangle is
displayed in the instrument cluster to instruct the driver to take over
control.
The standard car phone works by way of the LINGUATRONIC voice activation
system, dialing and storing numbers by simple voice prompts.
Another innovative feature is active ventilation to keep seats
perspiration free, and dynamic, multi-contour backrests that gently
massage the spine to keep occupants fresh on long journeys.
Warranty is two years/unlimited distance, while the normal Mercedes-Benz
six year/120 000 km maintenance plan that requires staggered customer
contribution as the mileage increases is also standard. Owners also have
the option of an extended maintenance plan (up to 200 000 km) and a
no-contribution option on maintenance costs.
The S-Class has a world market share in its segment (top-end luxury cars)
of over 54%. In SA, its market share is 70% of the class. The diesel
derivative will, without doubt, significantly broaden its base. At
R589000 it's bound to put a dent of some sort in almost any size bank
balance, but fortunately, its sober habits will help contain the damage.
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