Mercedes also revealed its new 15.6-litre, inline,
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Mercedes also revealed its new 15.6-litre, inline, six-cylinder engine, the 0M473, offered in both the Arocs and the Actros. This is Mercedes' fifth new truck engine in less than two years. It completes Mercedes' Euro-6 engine range, which boasts a smooth progression in terms of both swept volume and power ratings, from 154hp to 617hp.
Available only as a Euro-6 engine, the 0M473 supersedes the 15.9-litre V8 0M502LA engine in the top Euro-5 Actros. Whereas the V8 comes in 503hp, 542hp and 590hp ratings, the new 0M473 ups the ante, to 510hp, 570hp and 617hp, with rated speed cut from 1,800 to 1,600rpm. Torque is better too, 200Nm more than the V8, with the 617hp unit reaching 3,000Nm.
Although Mercedes has no plans to gatecrash the Swedish 700hp-plus club, head of truck product engineering Georg Weiberg said we can expect to see more than 617hp from the 0M473 once testing has proved that higher power does not jeopardise durability.
The key features of the new engine echo those of the 12.8-litre 0M471, namely twin overhead (hollow) camshafts and Bosch/Daimler amplified common-rail fuel injection (dubbed X-Pulse by Mercedes). The latter provides injection pressures of up to 2,100bar along with rate shaping by means of pilot, main and post injections for each firing.
Unlike the 12.8-litre engine, this new 15.6-litre unit uses turbo-compounding. Its Holset turbocharger is followed by a second turbine that extracts the thermal energy from the exhaust stream and feeds it back to the engine's crankshaft via a hydrodynamic clutch (fluid coupling) to supplement output. But the turbine is spinning at approximately 60,000 rpm, so two stages of reduction gears are needed to bring the speed down to match the engine's 1,500rpm.
Turbo-compounding only pays dividends if the engine is working hard, when there is lots of energy to be harvested from the exhaust. Daimler reckons turbo-compounding gives fuel savings of around 2% under high load conditions. So the 0M473 will shine at high weights and in mountainous terrain rather than taking life easy at 40 tonnes and 1,000rpm on the Ml.
Like its two smaller siblings in the new OM engine range, the 0M473 has a powerful integral three-stage decompression brake, better known under its proprietary 'Jake brake' name from US-based Jacobs Vehicle Systems.
NOx reduction is handled by cooled EGR in the engine, plus SCR exhaust-after-treatment. The 0M473's dry weight is quoted as 1,284kg, which we understand to be about 100kg more than the current 15.9-litre V8. It is also 150kg more than the 12.8-litre 0M471, which has ratings up to 503hp.