Citaro: BlueEFFICIENCY Power Euro VI engines

Cutting-edge technology for a new era.

Mercedes-Benz has played a pioneering role in the development of environmentally friendly, innovative drive systems for many years now. With its efficient and powerful BlueTec engines, the company has succeeded in reducing fuel consumption while drastically reducing harmful emissions. Mercedes-Benz has set another benchmark in the form of BlueEFFICIENCY Power technology.

The first regular-service bus with Euro VI.

Specifically developed for the European market, tested and proven in the toughest of conditions from the Arctic Circle to Southern Europe, the BlueEFFICIENCY Power drive system is deployed in the Citaro. The OM 936, OM 936 h and OM 470 engines with outputs ranging from 220 to 290 kW already met the new Euro VI exhaust gas emissions standard two years before it came into effect.

The powerful, efficient, future-proof engine ensures a drastic reduction in nitrogen oxides and particulates in the exhaust gas. The Citaro is the pioneer of a generation of environmentally responsible regular-service buses.

A milestone in engine development.

The BlueEFFICIENCY Power engines with BlueTec 6 are impressive not only for their high standards of environmental compatibility but also for their excellent economy. Despite the more demanding requirements the engineers have succeeded in keeping fuel consumption as low as usual. Consumption unchanged, despite Euro VI – a new milestone has been marked out by Mercedes-Benz.

This has been made possible by Common Rail Technology, amongst other innovations. In addition to the superlatively low emissions resulting from the combination of SCR technology, demand-oriented exhaust gas recirculation and particulate filters, there is the superlatively high performance of the engines thanks to new turbocharging technology. Delivering optimum performance, an extremely smooth ride and easy handling.

A further advantage – the recuperation module.

The recuperation module regulates the power management and thereby reduces fuel consumption.

When the vehicle brakes, the alternators delivery free electricity (from the deceleration energy), which is briefly buffered in the capacitors. When the bus starts off again, the capacitors supply the on-board electrical system. The alternators continue running during idling in order not to stress the engine (torque).

Hybrid technology for the drive system.*

What is better for transport companies the environment: independent hybrid bus models or economical hybrid technology available as optional equipment?

Mercedes-Benz has opted for an innovative hybrid module which is a world first, allowing hybrid technology to be selected as optional equipment for a broad range of buses and coaches with the OM 936 diesel and M 936 natural-gas engines. Instead of expensive stand-alone hybrid buses, numerous models benefit from an inexpensive and efficient hybrid technology.

The efficient and compact hybrid module was specially developed for the demands of regular-service buses in towns and busy urban areas. It assists the consumption-optimised diesel and natural-gas engines of our urban buses and thus stands for economy and sustainability. The implementation of our hybrid module is unproblematic both for drivers and workshops as the selection of the "Hybrid module" optional extra results in only minimal modifications to the basic vehicle. That also ensures that our hybrid technology is particularly affordable in terms of procurement.

The module achieves a fuel saving of as much as 8.5 %, depending on the operational route and vehicle version. Thus the additional costs can be compensated for within the space of just a few years; the environment, meanwhile, benefits from the new technology right from the outset. The compact hybrid system makes your bus a highly economical and ecological all-rounder. And that means that you have the perfect combination between economy and sustainability.

More power, less consumption.

The hybrid module is designed to be both simple and robust: a disc-shaped electric motor is integrated in the drivetrain between the engine and the transmission. Two batteries are installed on the roof. Plus, there is also the voltage converter and an intelligent pulling-away management system with adapted engine control. The electric motor and voltage converter have their own coolant circuit.

In line with this, there is one important factor to bear in mind: just like the Mercedes-Benz passenger cars equipped with a hybrid drive, our hybrid module technology uses a separate 48-volt electrical system. That means that we completely do away with a complex high-voltage system and the associated safety requirements which such a system requires.

The technology operates as simply as it is designed: if the bus drives is coasting or braking, the electric motor works as a generator and creates electricity without using fuel to do so. The power generated in this way is stored as electrical energy. In higher load situations, such as when pulling away, so-called boost phases, the electric motor assists the diesel or gas engine with additional torque by calling on the energy stored in the supercaps. This relieves strain on the combustion engine and thus also means lower fuel consumption. The motors used in the hybrid module correspond to the output values of the combustion engines. The torque generated by the electric motor in the boost phase is used entirely for saving fuel. If sufficient energy is stored in the supercaps, the electric motor can also provide assistance during idling and thus also improves the efficiency of the combustion engine.

The Power Boost System (PBS).

Even better response is provided by the new Power Boost System (PBS). In brief, this technical refinement will be available for the engine rated at 260 kW. The new system is designed to guarantee better "sprint performance" when moving off, particularly on topographically demanding routes.

To achieve this, the Power Boost System pumps compressed air from the standard compressed-air system into the engine's intake tract, thereby briefly increasing air throughput. This in turn results in momentarily increased short-term starting torque, which can prove invaluable at bus stops located on inclines.

* Optional equipment