The pace-maker in environmental protection, economy and technology – Mercedes Benz Citaro and eCitaro offer tailor-made low-emission and locally emission-free drive technologies respectively

• Citaro with diesel engine: undercuts emissions limits in practical operation
• Citaro with gas engine: with biogas or biomethane almost CO₂-neutral
• Citaro hybrid: further-optimised combustion engine
• eCitaro: fully-electric drive – the new way to e‑m obility

The Mercedes-Benz Citaro and eCitaro make up a large family which offers the right drive technology for almost any application. Available for selection are the fully-electric and locally emission-free eCitaro, the Citaro with low-emission and extremely economical diesel engines, almost CO₂-neutral gas engines (when used in conjunction with biogas and biomethane), as well as well‑thought-out and economical hybrid technology for diesel and gas engines.

Citaro with diesel engine: undercuts emissions limits in practical operation

Transport companies can select from numerous drive variants for the Citaro. The basis of these are the clean and extremely economical diesel engines equipped according to the Euro VI emissions standard. As independent tests confirm, the engines undercut the prescribed emissions limit values in practical operations, in some cases even drastically.

The basis of the powertrain is the compact and light-weight Mercedes‑Benz OM 936 six-cylinder installed either upright or horizontally. From its 7.7 litre displacement, it delivers an output of 220 kW (299 hp) and torque of 1200 Nm. Upon request, the OM 936 is also available in some Citaro variants with an output of 260 kW and 1400 Nm of torque. If high pulling power is in central focus, the larger Mercedes‑Benz OM 470 with 10.7 litre displacement is the right choice. With 265 kW or 290 kW (360/394 hp) and 1700 Nm or 1900 Nm of torque, the engine is particularly powerful and fulfils the greatest of demands, notably in articulated buses like the spacious CapaCity.

Citaro with gas engine: with biogas or biomethane almost CO₂-neutral

The switch-over to electric drive systems in urban buses is a complex topic and requires extensive preparations. Thus, the rapid and comparatively less cost‑intensive option to implement an especially environmentally friendly intermediate technology is the Mercedes‑Benz Citaro NGT hybrid with natural‑gas drive. Gas engines emit almost no particulate matter and NO_x emissions are also very low. When used in conjunction with biogas or biomethane, the Citaro NGT hybrid is almost Co₂-neutral. The Mercedes-Benz M 936 G with its 7.7 litres of displacement is based on the OM 936 diesel engine. With 222 kW (302 hp) of output and 1200 Nm of torque, its performance is on a par with the diesel engine. The Citaro NGT is available both as a solobus and an articulated bus. The gas bottles of the Citaro NGT are made of light-weight yet highly resistant composite material and are installed on the roof.

Citaro hybrid: further-optimised combustion engine

The Citaro hybrid is an outstanding example for the economy in regular-service buses. For the first time worldwide, Mercedes‑Benz is offering hybrid technology as part of the optional equipment for a broad range of urban buses powered by diesel or gas engines. The Citaro hybrid combines with the equally new "intelligent eco steering" electrohydraulic steering to reduce the fuel consumption of the already efficient Citaro by as much as a further 8.5 percent. The Citaro hybrid is light, affordable to procure and unproblematic for drivers and workshops alike. A central aspect of it is the remarkable economy – the Citaro hybrid truly pays off.

The basic function of the Citaro hybrid is very simple: The additionally installed electric motor works during deceleration of the bus as a generator and converts braking energy into electrical energy. This electricity is saved in double-layer capacitors, known colloquially under the term "supercaps". It is then made available to the electric motor in order to assist the combustion engine, particularly when pulling away. The electric motor's maximum output is 14 kW, whilst its torque is 220 Nm. The energy storage unit is made up of two modules whose functionality corresponds to that of the proven recuperation modules of the regular Citaro. To ensure space savings, these are installed on the roof. Total capacity lies at a maximum of 1 Ah.

Mercedes‑Benz optionally combines all combustion engines with an automatic transmission featuring a torque converter from either ZF or Voith. What's more, Mercedes-Benz has lowered fuel consumption and thus also emissions and operating costs by means of numerous individual measures. For example, the Citaro saw the recuperation module being implemented for the first time: Double-layer capacitors – so-called supercaps – serve as an intermediary storage location for electrical energy. They assist active battery and generator management whilst also lowering fuel consumption. Especially low entrances are comfortably accessible to passengers and reduce the consumption of compressed air for "kneeling". The optional "intelligent eco steering" electrohydraulic steering provides needs-based and thus more fuel-efficient power assistance.

eCitaro: fully-electric drive – the new way to e‑m obility

The fully electric eCitaro sees Mercedes-Benz opening up a new chapter in electromobility. The two-door and three-door versions of the two-axle solobus are driven by an electrical axle featuring motors at the wheel hubs. Their peak output is 2 x 125 kW, while torque is 2 x 485 Nm. As is customary for this type of system, the performance is available from the start and, thanks to a two-stage transmission ratio, it is boosted to around 2 x 11,000 Nm. The supply of electrical energy is handled by a modular system featuring up to twelve battery packs with a combined maximum capacity of 292 kWh. Especially noteworthy is the innovative, highly efficient and thus energy-saving thermal management system used in the eCitaro.

It is already planned that the next battery generation with greater capacity and a corresponding range increase will be able to be integrated. Another step already scheduled during that same period envisages the optional use of future lithium-polymer batteries, also referred to as solid-state batteries. Subsequently, it is anticipated that the range of the eCitaro will be increased yet again, this time by means of a Range-Extender in the form of a fuel cell for generating electricity from 2022. It will be designed to allow the eCitaro to fulfil nearly 100 percent of all requirements of urban buses.