Friday, 3 July 2015
Daimler declares OM471 as a “masterpiece”
No other heavy-duty engine platform surpasses this figure or has proven itself so often, claims
its technical features and the resulting capabilities and qualities, the heavy-duty engine took engine manufacturing for heavy-duty commercial vehicles into a brand new era.
The 12.8-litre in-line six-cylinder unit made its mark with a robust design and technical innovations with significant benefits for the customer. Key features included a compacted graphite iron (CGI) cylinder head (according to Daimler's PR office), twin overhead composite camshafts, the single common rail fuel injection system with X-Pulse pressure booster, the asymmetric exhaust gas turbocharger, the powerful engine brake and emission control based on SCR technology, exhaust gas recirculation and particulate filter in order to meet the stringent Euro VI emissions requirements.
A key component of the new generation of engines is the latest-generation X-Pulse injection system. This “unique” common-rail system with a pressure booster or intensifier in the injector has, according to Mercedes, unrestricted flexibility for modelling the injection system. Maximum rail pressure has been increased from 900 to 1,160 bar, resulting in a maximum injection pressure of 2,700 bar.
The injection nozzle is an eight-hole nozzle (previously seven holes), increasing maximum flow rate by around 10 per cent.
Additional modifications include the piston bowl geometry, the sizeable increase in compression ratio from 17.3:1 to 18.3:1, along with a reduced exhaust gas recirculation rate (EGR rate).
These measures add up to a further improvement in efficiency across the entire engine performance map, according to Mercedes engineers. This in turn lowers fuel consumption significantly. The optimum values in the consumption characteristic map have followed the new torque curve towards lower engine speeds.
Systematically configuring the engine for low fuel consumption means that untreated NOx emissions rise. This is countered by the SCR technology featuring an “innovative and efficient” SCR catalytic converter. AdBlue consumption is said to be “on a par” with earlier Euro V engines at around 5 per cent of fuel consumption.
Mercedes claims the OM 471 is “one of the most powerful diesel engines in its class” with an output of 30.5 kW (41.4 bhp)/litre displacement and a torque of 203 Nm/litre displacement.