It is no surprise that Mercedes-Benz has sold 5,000 units of its Citaro Euro 6 urban buses in just over two years of its market launch. The Citaro was the first series production city bus globally to comply with the Euro 6 emission norms, apart from its numerous successes in its 18-year journey, with more than 40,000 buses already in operation in over 40 countries.
Recently, Daimler unveiled its latest Citaro NGT (Natural Gas Technology) with impressive NVH (Noise-Vibration-Harshness) and CO2 emission levels. This article examines the virtues of the Citaro range of low-floor city buses by taking specific illustrations from its latest NGT variant and the Citaro GÜ Euro 6 models that are sold in Switzerland.
The pinnacle of the Citaro bus range is its design and construction. The salient exterior design consisting of sleek headlamps and the tri-star logo, with its noticeable A0-pillars, large frontal windscreen and side window areas, and an attractive design-detailing is impressive. The interiors are equally good-looking and innovative, for instance, the cantilever seating in the frontal part of the cabin. The ‘continuous annular frame’ construction is light weight and extremely strong providing enhanced cabin stability and safety.
Further, the Citaro’s standardised modular assembly gives an edge over its rivals in terms of construction cost and flexibility in varied applications. The Citaro range consists of solo, articulated, and short-wheelbase (LowEntry) bus variants. This includes standard 12m twin-axle, 15m or 18m tri-axle, and a 20m four-axle (articulated) configurations. The commonality of parts between these models and shared assembly keeps the production costs low, in addition to a wide range of products that practically cover all the needs of urban operations. Furthermore, a free choice of equipments and powertrain options as per customer requirements makes the Citaro range more appealing.
Let’s take the example of the Citaro GÜ Euro 6. This 18m articulated version is part of a 90 bus order for Switzerland, a key maker for Mercedes-Benz buses in Europe. As per the buyer’s customized order, these buses boast bi-xenon headlamps, LED daytime running lamps, double-glazed side windows, and a reversing camera. A video surveillance system with 6 cameras across the vast cabin the interior, LED interior lighting, an integrated IBIS
on-board info system, and a passenger counting system is also included in the package.
In addition, to batter the snowy roads, a compartment for snow chains behind the rear axle is provided. There are three electrically operated doors, of which doors 2 and 3 are pivoting sliding doors to augment easy flow of passengers into the cabin. The buses can accommodate 73 standing and 56 seated passengers each, and all seats are seat-belt secured.
The Citaro GÜ Euro 6 is powered by six-cylinder 10.7-litre OM 470 BlueEfficiency diesel engine that can make up to 360 hp of max power and a peak torque of 1700 Nm at 1100 rpm. This common-rail engine features X-Pulse pressure boosters for fuel efficiency, and an exhaust gas re-circulation and particulate filter in order to meet the stringent Euro 6 emissions standards.
The Citaro NGT, on the other hand, is presented as an attractive alternative to the diesel-powered Citaros by gaining on improved NVH and CO2 emissions levels. Already on sale in Germany, the latest natural gas (CNG) run Citaros are powered by a 7.7-litre M 936 G natural gas engine with an output of 302 hp and 1200 Nm of max power and torque. This engine essentially OM 936 turbodiesel unit, used in Citaro and Citaro G Euro 6 models, modified for CNG compatibility. Mercedes Benz is constantly downsizing its engines that run on natural gas, making the Citaro NGT 25 percent lighter than its predecessor with a 12.0-litre natural gas engine. The standard final drive ratios of the CNG engines are made a step shorter than their diesel counterparts, owing to different engine speed in natural gas.
The 227-litre gas tanks for the Citaro NGT are made of composite, light-weight materials including a carbon-fibre made casting. The company claims that the new NGT is 15 to 20 percent efficient over the previous models. The all-round disc brakes are standard across the whole Citaro range, assisted with ABS and EBD. Moreover, the variants get latest electronic system FPS (flexibly programmed control) based on a CAN databus system with decentralised electronic modules, and a holistic diagnostic system.
The Citaro range is in its second generation, and has already crossed 40,000 units mark (in April 2014) in terms total sales since its inception in 1997. It is manufactured primarily in Mannheim, Germany, apart from France and Spain. The buses are available in Euro 4, Euro 5 and EEV (Enhanced Environmentally friendly Vehicle) certifications, apart from the latest Euro 6 variants.
Conventional mobility apart, Mercedes-Benz has even unveiled Citaro G BlueTec Hybrid, a series-hybrid articulated bus that draws power from four 80 kW wheel hub motors located on the centre and rear axles. A four cylinder 4.8-litre diesel engine charges a roof-mounted 19.4 kWh lithium-ion battery pack to propel the electric motors. The company is also working on a hydrogen fuel cell-powered version Citaro BZ that is currently under
feasibility trail runs.