Following the successful market launch of the Actros long-distance trucks with BlueTec diesel technology at the beginning of 2005, Mercedes-Benz has now presented the construction vehicles in the Atego, Axor and Actros truck series. In order to comply with the stringent limits imposed by coming exhaust emission standards while achieving a significant advantage in fuel consumption, Mercedes-Benz has uncompromisingly decided in favour of SCR technology for all European trucks.
Daimler-Chrysler already presented a complete family of long-distance trucks with SCR technology under the name "BlueTec diesel technology" at the 2004 International Commercial Vehicle Show. SCR stands for Selective Catalytic Reduction. This fleet presented one year ago is available in a BlueTec 4 version to comply with the Euro 4 standard coming into force in October 2006, as well as in a BlueTec 5 version. The latter version, which is chosen by 98 % of customers, already betters the Euro 5 standard which is not due to come into force until October 2009.
With an up to 80% reduction in harmful exhaust emissions and a demonstrably lower fuel consumption, Mercedes-Benz trucks with BlueTec technology represent an environmentally friendly and at the same time economically unrivalled transport solution for the long-distance road haulage of the future.
Since deliveries commenced at the beginning of 2005, the demand for these particularly low-emission long-distance trucks in the Actros series has been very strong. In addition, the previously only internally verifiable claims for this future-proof SCR emission control technology have clearly been proved justified by considerably reduced fuel consumption. During their exacting comparative tests, numerous European specialist publications have established beyond doubt that Actros semitrailer tractors consume significantly less diesel fuel than competitors, some of whom try to meet the limiting values of the coming Euro 4 standard with other technologies such as exhaust gas recirculation.
BlueTec technology is the benchmark for the industry
Moreover, as of autumn 2005 Mercedes-Benz is still the only European manufacturer to offer its customers the option of vehicles with clean exhaust gases according to the Euro 5 standard applicable from 10/2009 – i.e. four years before it comes into force. Five out of seven European truck brands have committed themselves to meeting the Euro 4 emission control standard and taking the even more stringent Euro 5 hurdle with the help of the SCR emission control technology favoured by DaimlerChrysler, while the other two brands are at least opting for this future-proof approach in the case of their Euro 5 models announced for 2006.
BlueTec versions of the Atego, Axor and Actros construction vehicles also ready
As the deadline of October 1, 2006 approaches, when the Euro 4 standard will become compulsory for all newly registered commercial vehicles, DaimlerChrysler is unveiling the fuel-efficient, low-emission BlueTec versions of its Atego, Axor and Actros construction vehicles. During the course of the coming year, Mercedes-Benz will have gradually extended the availability of BlueTec for all its truck series so that customers can choose from a full range of long-distance, distribution, construction and special-purpose vehicles.
The four and six-cylinder in-line engines in the Atego and Axor employ exactly the same basic technology which has proved so successful in the Actros long-distance models 1844 to 2548 with a V6 engine for more than half a year, and with 5000 units in day-to-day operation. As is already the case for the current Euro 3 versions from the 900 engine series, the evolutionary OM 900 BlueTec features consistent and well-proven technology down to the smallest component.
No alternative to diesel
With the BlueTec technology employed by DaimlerChrysler, an optimised combustion configuration minimises the development of harmful particulates from the start and noticeably reduces fuel consumption. Exhaust gas aftertreatment based on SCR ensures the necessary reduction of nitrogen oxides and contributes to a further significant reduction in particulate emissions. As a result the stringent legal requirements of the Euro 4 and Euro 5 standards are combined with a considerably lower fuel consumption compared to Euro 3.
AdBlue for 3000 to 7000 km on board
The reduction agent required to neutralise the nitrogen oxides is known as "AdBlue". The consumption of AdBlue for Euro 4 vehicles amounts to three to five percent of the diesel fuel consumption. In the case of a 7.5-tonne Atego it may be expected to be less than one litre per 100 km. Given a tank capacity of 25 litres, for instance, this corresponds to a range of 3000 km or more.
In the past the exhaust emission standards Euro 1 to Euro 3 always involved a compromise, as a combustion configuration designed for low particulates together with a low fuel consumption naturally produced higher levels of nitrogen oxides, and vice versa. Now that this thermodynamically inevitable conflict of aims has been resolved by the use of external SCR emission control, the next evolutionary stage of the 900 engine series has been emphatically configured for a low fuel consumption and low particulate emissions.
Further engine development: all components under high pressure
One of the major measures used to ensure lower untreated emissions and a further reduction in fuel consumption in the basic engine is an increase in the compression ratio to 18.5:1. This is accompanied by an increase in the maximum ignition pressure from 180 to 190 bar. The fully electronic Telligent engine management system controls the mode-selective fuel injection process via newly developed 9-hole injection nozzles.
In order to ensure the necessary durability for this much more energy-efficient combustion process, numerous features of the 900 engine series were redesigned. This involved new materials and modified components: optimised piston rings, new crankshaft and connecting rod bearings and more durable seals have been incorporated into the evolutionary package for the BlueTec engines in the 900 series.
As a result of these and numerous other measures, the new BlueTec generation of particularly low-emission and fuel-efficient in-line four and six-cylinder engines has been further improved with respect to reliability and long-term durability. At the same time BlueTec diesel technology requires neither the availability of low-sulphur fuel nor shorter oil-change and service intervals, therefore there are no new limitations to the operating range of BlueTec vehicles. The use of conventional lubricants is also no problem. All in all, a commercial vehicle with SCR technology on board behaves no differently from a current Euro 3 vehicle.
BlueTec components at a glance
- AdBlue tank with fluid level sensor and heater
- AdBlue intake line (heated)
- AdBlue supply unit (heated)
- AdBlue pressure line (heated)
- AdBlue metering unit (heated)
- Compressed air regulator
- Metering line
- Spray unit
- Control unit (integrated into the Telligent engine management system)
- SCR frame module
- Catalytic converter
AdBlue is sucked from the tank by the supply unit and fed to the metering unit via a heated supply line. The supply unit is mounted on the frame near the tank, while the metering unit is engine-mounted. The compressed air regulator supplies compressed air to the AdBlue metering unit in sufficient quantity and at the right pressure. In the metering unit the requisite quantity of AdBlue is sprayed into the hot exhaust gases by compressed air via the metering valve, ensuring a uniform distribution of AdBlue in the exhaust gases. This even distribution is of decisive importance for the hydrolysis of AdBlue, and therefore for the efficiency of the catalytic converter.