Mercedes-Benz Citaro OM906LA Engine start & Revving up

Recorded with iPhone 12 Pro 📱
The vehicle in question is a 2006 Mercedes-Benz Citaro 12m pre-facelift with OM906LA Euro 3 making 280 HP🚌
📖Story time:
The OM906 is a series of 18-valve Inline 6 OHV Diesel engines developed by Mercedes-Benz and released in the late 90's. It was designed for industrial & heavy-duty applications. Some notable usage of this series of engines were in smaller truck offerings and urban buses of Mercedes-Benz, including the Axor, Atego, Econic, and Claas Tucano combine harvesters (all of them having the OM906LA).
On the Mercedes-Benz Citaro there were two versions of the engine: The OM906hLA was designed only for the Citaro buses with the more common horizontal placement for the engine. The nomenclature h means horizontal engine mount. The OM906LA however was put on the less common variant of the Citaro with vertical engine placement, such as the one in the video.
This series of engines is compliant with Euro 2, Euro 3, Euro 4 & Euro 5 emission norms, depending on the revision of the engine. Euro 4 & Euro 5 versions are compatible with AdBlue due to the emission standard's requirements.