The toughest sections of the off-road course south of Berlin highlight the familiar strengths of the short-nosed Unimog: its outstanding handling characteristics in difficult terrain. Off-road deployment in extreme conditions is the order of the day for these vehicles, according to Mercedes-Benz. For clearing heavy snow, fighting forest fires, disaster relief, crane operations, pipeline construction, on expeditions, on rescue and recovery missions, and last but not least, in passenger transport – the natural habitat of the U 4023 and U 5023 begins where roads give way to rough tracks and open country. An array of equipment developed by specialist equipment and body manufacturers means that the Unimog can master difficult tasks, even in tough terrain.
In the new generation, these have been improved even further, thanks to the altered position of the engine, according to Mercedes-Benz.
In 2013, Mercedes-Benz introduced diesel engines for the entire commercial vehicle range which conformed to the Euro VI emissions standard well ahead of the norm coming into enforcement. At the same time, the extreme off-road version of the Unimog also underwent a complete redevelopment to feature a mid-engine design. The engine has been shifted a metre to the rear, which helps not only accommodate the assemblies that Euro VI made necessary, but also enables direct power take-off from the engine. This means that devices can work independently of the vehicle being driven. Transmission power take-off also remains possible.
The Euro VI diesel engine is the heart of the new mid-engine concept. The engine is the new high-torque OM 934 BlueTec 6 engine; a four-cylinder unit with an output of 231 hp and a displacement of 5.1L. Exceptionally efficient, the assembly provides a higher torque of 900 Nm, which is available consistently over the entirety of the principal driving range from 1200 rpm to 1600 rpm. The technical top speed of 90 km/h is quite adequate for longer journeys and motorway driving, according to the automaker.
Despite the added engineering complexity required to meet the Euro VI criteria, the new all-terrain Unimog combines low fuel consumption with reduced emissions, great reliability, a long life expectancy and long maintenance intervals. Alongside cooled exhaust gas recirculation within the engine, emission control features a successively switched system comprising a closed particulate filter, AdBlue injection and an SCR catalytic converter. A particularly positive aspect: for the new Unimog with Euro VI engines, fuel consumption has been reduced by up to 3 percent. This means that the engines, which already produce up to 90 percent less emissions and particulate matter than the previous models, are even more environmentally friendly.
The transmission of the Unimog has been optimized and uprated, resulting in shorter shift times whilst also extending its service life. The transmission is operated via a steering-column lever, which is also used to control the electronic quick reverse (EQR) function. As in the previous version, eight forward and six reverse gears are available and there is also an optional off-road group for off-road use in the speed range between 2.5 and 35 km/h.
Safety has also been improved: the new engine brake is a double-speed decompression brake which, in the case of the OM 934, develops braking power of up to 180 kW. Each cylinder in the engine has its own engine brake unit. The high braking efficiency considerably reduces wear and tear on the wheel brake systems, thus greatly improving the overall economy. Offroad ABS comes as standard, according to the automaker.
As with all Mercedes-Benz commercial vehicles, the new model designations of the big Unimog include the horse power number: 230 in this case. The first two digits of the designation stand for the vehicle type. The biggest differences between the two models come in the form of the axles and frames, which thus affect the axle loads and gross vehicle weight. In the case of the U 4023, this is a maximum of 10.3 t, for the U 5023 a maximum of 14.5 t, according to the company.