Mercedes-Benz OM 457
The OM 457 is a diesel engine from the Mercedes-Benz brand. It is listed as an in-line six-cylinder engine and was manufactured from 2003 to 2012. It was available in three Euro standards: 3, 4 and 5.
| Daimler | |
|---|---|
 OM 457 hLA for longitudinal installation at the rear left with flanged automatic transmission from a Citaro |
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| OM 457 | |
| Production period: | since 2003 |
| Manufacturer: | Daimler |
| Working principle: | diesel |
| Motor design: | Inline six-cylinder |
| Displacement: | 11,967 cm 3 |
| Mixture preparation: | Pump-line-nozzle |
| Engine charging: | Turbocharger with intercooler |
| Power: | 185-335 kW |
| Dimensions: | 1065 kg |
| Previous model: | Mercedes-Benz OM 447 Euro II |
| Successor: | OM 47x series |
technology
The OM 457 is a water-cooled four - stroke diesel engine with pump-line-nozzle injection. It was developed for driving vehicles. It can be installed lengthways or crossways. The displacement of 11,967 cm³ results from a bore of 128 mm together with a 155 mm stroke. The engine firing order is 1 - 5 - 3 - 6 - 2 - 4, the direction of rotation of the crankshaft is counterclockwise. The OM 457 is available in several variants for the Euro III to Euro V emissions standards in the 185–335 kW output levels.
Motor housing and crank drive
The cylinder block and the crankcase are made of gray cast iron , the crankshaft with seven bearings is forged and has screwed-on counterweights. The power is transmitted from the pistons to the crankshaft via forged connecting rods . The engine has single cylinder heads made of gray cast iron, which are screwed on with stud bolts. Coolant, fuel and oil ports as well as oil coolers, pump-nozzle units and oil spray nozzles are integrated in the engine's crankcase. The engine oil pan is made of an aluminum alloy and has a capacity of 27 liters. It must contain at least 16 liters for proper operation, not including the volume of the oil filter.
camshaft
The OM 457 has a lateral underlying , seven-mounted camshaft. It is driven by the flywheel via a spur gear. A gear is attached to the spur gear of the camshaft that drives the air compressor and the pump for the power steering. At the end of the camshaft there is a gear that drives the fuel pump. The camshaft per cylinder has one inlet and one outlet cam, as well as another cam that actuates the pump-nozzle unit.
Valve train
The camshaft actuates two hanging inlet and outlet valves (OHV) per cylinder via tappets , push rods and rocker arms . The inlet valves are connected via a horizontal cross member (valve bridge), the same applies to the outlet valves. The rocker arms, which are arranged at a 45 ° angle, act on the center of these crossbars. Unlike a four-valve system with two overhead camshafts (DOHC), intake and exhaust valves are controlled by the same camshaft and there are only two cams for four valves.
piston
The pistons are made of an aluminum alloy and have a graphite coating below the piston rings. With a diameter of 128 mm, they have a height of 140 mm. The mass of the pistons is 2470 g. The pistons have three piston rings. The first piston ring is a chrome-ceramic-coated trapezoidal ring made of gray cast iron. The second piston ring is conical and chrome-plated, the third piston ring is made of cast iron with a beveled edge and a ring spring. A cooling channel that is fed by cooling oil runs inside the piston. The combustion chamber in the piston (the piston bowl) is divided and has a capacity of 93.6 cm³. The piston crowns are cooled by oil spray nozzles in the crankcase, the piston pins have a diameter of 52 mm.
Fuel system
The fuel is injected into the cylinder through six- or seven-hole nozzles with up to 1800 bar, which are connected to pump-line-nozzle units via relatively short high-pressure lines. In contrast to a common rail system, each cylinder has its own high-pressure pump with its own high-pressure circuit. The pump-nozzle units are located next to the cylinders and are operated directly by the camshaft below. The amount of fuel is controlled by the control unit with solenoid valves. The required fuel first flows from the fuel tank into the fuel cooler, which is attached to the crankcase. From there the fuel runs into the fuel pump, which pumps the fuel into the fuel filter. The fuel filter is heated and is equipped with a water separator for countries with poor fuel quality (primarily Eastern Europe). The fuel flows from the fuel filter into the unit injectors. Excess fuel is first fed to a pressure control valve via a leakage line, which returns the fuel to the fuel pump. Excess fuel flows back into the tank from the fuel filter leakage line. Diesel fuels according to EN 590 or EN 14214 can be used as fuels .
Cooling system
The cooling system has a water cooler and has a capacity of 15 liters, which is circulated by a feed pump with a flow rate of 7.7 liters per second at the rated engine speed. From a temperature of 83 ° C the thermostat opens the valve from the engine water circuit to the water cooler, from 95 ° C it is completely open. The maximum water temperature should be 100 ° C. In addition to the water cooler, the engine also has a fan, which is available in two versions. The first variant has an oil-hydraulic clutch, the power transmission of which depends on the viscosity of the oil. As the engine temperature rises, the viscosity of the oil changes, causing the fan to spin faster. The disadvantage of this variant is the inertia. The second variant has an electromagnetic clutch that can control the fan speed more precisely. The coolant in the engine should be replaced at least every three years.
Auxiliary units
The engine is charged by a BorgWarner exhaust gas turbocharger with fixed guide vanes. The charge air is cooled by a charge air cooler before it reaches the intake tract. In accordance with the Euro 5 emissions standard, the exhaust gas is cleaned with an SCR catalytic converter and AdBlue. The air compressor for the compressed air system delivers 890 liters per minute with 12 bar system pressure and rated motor power. The electrical system works with 24 volts and is supplied with voltage by up to two V-ribbed belt-driven alternators . A starter with 7 kW power is used to start the engine .
Technical specifications
| OM 457.951 LA | |
|---|---|
| Engine description | |
| Bore × stroke, displacement | 128 x 155 mm, 11967 cm³ |
| Engine type | Six-cylinder in-line engine |
| Working principle | Four stroke diesel engine |
| Mixture preparation | Pump-line-nozzle |
| Engine charging | 1 × turbocharger with fixed guide vanes, intercooler |
| cooling | Water cooling |
| Compression ratio | 18.5: 1 |
| Direction of rotation of the crankshaft | Counter clockwise |
| General data | |
| Minimum start temperature when the battery is 75% charged | −20 ° C |
| Starting speed at −20 ° C | 100 min −1 |
| Maximum permissible motor temperature | 100 ° C |
| Maximum permissible alternator temperature | 80 ° C |
| Performance data | |
| rated capacity | 260 kW at 2000 min -1 |
| maximum torque | 1600 Nm at 1100 min -1 |
| Standard idle speed | 560 min −1 |
| Minimum idle speed | 510 min −1 |
| Maximum speed | 2360 min −1 |
| Minimum load speed | 1000 min -1 |
| Maximum operating altitude above sea level | 2000 m |
| measures and weight | |
| Dimensions (length × width × height) | 1316 × 746 × 1019 mm |
| Mass (dry) | 1045 kg |
| Ground (ready for use) | 1065 kg |
| Power to weight ratio (dry) | 4.02 kg / kW |
| Power-to-weight ratio (ready for operation) | 4.1 kg / kW |
| Charge air system | |
| Turbocharger boost pressure | 1.35 bar at 2000 min -1 |
| Maximum allowable boost pressure | 1.4 bar at 2000 min -1 |
| Maximum permitted drop in boost pressure | 0.1 bar at 2000 min −1 |
| Charge air temperature after the compressor wheel | 145 ° C |
| Charge air temperature after charge air cooler | 40 ° C |
| Fuel system | |
| fuel | Diesel fuel according to EN 590 or EN 14214 with 51 CZ |
| Fuel consumption at nominal power | 202 g / kWh |
| Fuel consumption at maximum power output | 184 g / kWh |
| AdBlue consumption in relation to fuel consumption | 3–5% |
| Exhaust aftertreatment substance | AdBlue according to DIN 70070 |
| Auxiliary units | |
| alternator | 2 × 28 V, 100 A |
| Starter | 24 V, 7 kW nominal power |
swell
literature
- Daimler Chrysler: Powersystems • Industrial Engines Maintenance and Repair Series 457, 500 and 900 Advanced Training . May 2003