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  • Mercedes-Benz OM 473 Diesel Engine - Torque

Mercedes-Benz OM 473 Diesel Engine - Torque

15.6 liters of diesel displacement with 2,200-plus lb-ft of torque

Mar 26, 2015
Photographers: Courtesy of Daimler
The Mercedes-Benz “BlueEfficiency Power” range of engines spans from a 5.1L four-cylinder that’s designed for delivery vehicles up to the 15.6L six-cylinder OM 473 engineered for heavy trucks. That diesel is the most powerful engine in the lineup, with ratings of up to 625 hp and 2,213 lb-ft of torque that’s available at just 1,100 rpm. It’s built to meet strict Euro VI emissions standards and has the power to move large loads while navigating European traffic over the demanding topography of the whole continent.
By the start of production, the OM 473 engine had covered 1.15 million test miles—including intense driving cycles in the Spanish Sierra Nevada, cold tests in Scandinavia, and endurance runs in South Africa. The engine was also pushed in overload conditions with double tractor-trailer combinations pulling 132,277 pounds (66 tons/60 metric tons). That’s in addition to five years of real-world operation by its Detroit Diesel cousin, the 15.6L DD16, with a number of those units having already covered more than 1,000,000 miles. While the engines share the same block design, the Mercedes-Benz version has more than 200 unique parts and is created at different manufacturing plants.
Photo 2/3   |   Mercedes Benz Om 473 Diesel Engine
The OM 473 uses a compound-turbo system for something the folks at Mercedes call “instant response,” with one conventional atmospheric turbo and a second, direct-drive turbo. The downstream unit transfers power to the drivetrain using a hydrodynamic clutch that’s connected to the engine’s gear drive, which is linked directly to the crankshaft. This helps it produce 1,844 lb-ft of torque at a little more than 800 rpm, with nearly the entire pulling power on tap from around 900 to 1,400 rpm.
The engine has a ribbed, gray, cast iron block; the head is made from compacted graphite iron (CGI) and uses 38 clamping bolts to handle cylinder pressures of more than 2,900 psi. The single-piece pistons are made of steel and travel inside wet cylinder liners, and the gear drive is mounted in the output side of the engine. It turns hollow dual overhead camshafts made of composite materials to minimize rotational losses. The six-hole injectors are controlled by the Mercedes-Benz X-Pulse system that continually adjusts events for each cylinder using “rate shaping” techniques. These operations change the injection timing, amount, quantity, and pressure based on operating conditions to maximize the power delivery, fuel mileage, and durability of the heavy-duty OM 473 in all driving conditions, ranging from gridlock to steep grade climbs.
Photo 3/3   |   The Mercedes-Benz OM 473 shares the same engine block design with the 15.6L Detroit Diesel DD16 that makes up to 600 hp and 2,050 lb-ft of torque and the 14.8L DD15 that makes up to 505 hp and 1,750 lb-ft. The American inline-six engines are EPA 2010 compliant and can be found in trucks such as the on-highway Freightliner Cascadia and the Western Star 6900 XD, which is used for logging, mining, heavy hauling, recovery, and more.
Specifications
Engine: Mercedes-Benz OM 473
Displacement: 15.6L (952 ci)
Engine layout: Inline six-cylinder
Power: 625 hp at 1,600 rpm
Torque: 2,213 lb-ft at 1,100 rpm
Engine braking: 625 hp three-stage Jacobs engine brake
Bore x Stroke: 5.47 x 6.73 inches (139 mm x 171 mm)
Compression ratio: 17:1
Injection: Six-hole injectors/30,458 psi (2,100 bar)
Valvetrain: Dual overhead hollow composite camshafts/four valves per cylinder
Induction: Compound atmospheric turbo/ hydrodynamic direct-drive turbo
Head Material: Compacted graphite iron
Block Material: Cast iron
Piston Material: Steel
Emissions: Euro VI compliant with EGR, DPF, and SCR
Engine Length: 4 feet 8 inches (1,425 mm)
Engine Width: 3 feet 8 inches (1,128 mm)
Engine Height: 3 feet 11 inches (1,212 mm)
Engine Weight: 2,831 pounds (1,284 kg)

Sources

Daimler
Portland, OR 97217
503-745-8000
www.daimler.com
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