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.

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.

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).

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.