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Engine Lubrication, Basic Function - GF18.00-P-1003A

Engine all (4xWD) 

Engine all (CAR) 

Overview 

This document contains information on:

G16140820Courtesy of MERCEDES-BENZ USA

Example illustration of engine lubrication, shown on engine 139.9 

G16140821Courtesy of MERCEDES-BENZ USA

Example illustration of engine lubrication, shown on engine 256 

G16140822Courtesy of MERCEDES-BENZ USA

Example illustration of engine lubrication, shown on engine 656 

General 

The engine lubrication system basically does the following:

Primary objective of engine lubrication is to minimize the wear of the friction partners. Engine lubrication takes place through engine oil.

Function requirements 

Function 

Wet-sump lubrication 

Wet-sump lubrication covers the following lubrication types:

The engine management control unit (3) reads in the pressure value from the pressure and temperature sensor (9) in the low-pressure oil circuit and, depending on the characteristics map, actuates the low-pressure control valve, which, in turn, regulates the pump output via the hydraulic control lines (E) as needed. The low-pressure control valve controls the oil flow quantity at the control piston (17.2) via the solenoid switch. The pressure is built up or reduced until the desired pressure level at the pressure and temperature sensor (9) in the low-pressure oil circuit is reached. The low-pressure control valve and the control pistons are integrated in the oil filter module (17). A rapid build-up of oil pressure during engine start is achieved by means of check valves that prevent the oil ducts from idling when the engine is switched off. Needs-based, emission-optimized piston cooling is realized via the low-pressure characteristic map regulation in combination with the adapted opening characteristics of the piston syringes.

IMPORTANT The oil pressure switch is used for permanently monitoring the lubrication system.

IMPORTANT Depending on the characteristics map, the pressure regulating valve is actuated with a ground signal from the engine management control unit (3) and regulates the engine oil flow volume.

To achieve the greatest possible fuel savings, the pressure switchover now includes the following functions:

The oil pressure pump sucks the engine oil from the oil pan (1) below the crank assembly and pumps it under pressure to the following components:

The oil pan (1) has the following functions:

The oil filter (17.3) prevents combustion residues, metal abrasion, and dust from getting into the oil. The engine oil heat exchanger (17.7) is connected to the cooling circuit; its primary task is to cool the engine oil.

IMPORTANT The coolant heats up more quickly than the engine oil. The waste heat from the coolant is used for heating up the engine oil more quickly.

Dry-sump lubrication 

Wet-sump lubrication covers the following components:

The oil pan (1) is replaced with an external oil container, which acts as a storage tank. In addition to the oil pressure pump, which is required for engine lubrication, another oil pump - the oil suction pump - is installed. The oil suction pump sucks engine oil permanently from the crank chamber and cylinder head. The engine oil that has been sucked out is fed continuously to the external oil reservoir. The oil pressure pump pumps the engine oil from the external oil reservoir back to the crankcase.

As a result of the dry sump lubrication, the engine lubrication is supplied with oil in the following driving situations:

Dry-sump lubrication has the following benefits:

Oil-pressure regulation 

Engine-speed dependent oil pressure pump:

The oil pressure pump is driven directly or indirectly by the crankshaft, i.e., the oil pressure pump is engine-speed-dependent. If the engine speed is too high, the oil pressure pump generates excess oil pressure, i.e. the actual amount of oil delivered is greater than what is needed. Pressure limitation/regulation is implemented via an overpressure valve or an additionally installed control valve in the oil circuit/on the oil pressure pump. The excess engine oil is pumped via a bypass back to the intake port or oil pan (1).

Pressure-dependent oil pressure pump:

Alternatively, the oil pressure can be regulated by a controllable oil pressure pump that adjusts the oil delivery quantity as a function of the pressure. As compared to the engine-speed dependent oil pressure pump, the pressure-dependent oil pressure pump has two circuits with different oil pressure levels. In this case, engine lubrication is divided into a low-pressure level and a high-pressure level. The system pressure in the high-pressure oil circuit is nearly constant across all operating states. The low-pressure level for supplying the rest of the engine is regulated by a characteristics map in the engine management control unit (3). This lowers the power loss of the engine oil pump (14.2) and the resulting power loss of the engine. If the oil delivery quantity is adjusted depending on the pressure, the fully variable engine oil pump (14.2), which forms the tandem pump (14) together with the vacuum pump (14.1), ensures the oil supply in the oil circuit. The delivery rate of the engine oil pump (14.2) is regulated via the high-pressure control valve (13) by means of the hydraulic control lines. The high-pressure control valve (13) is also connected to the high-pressure oil circuit via a control line. Depending on the system pressure in the high-pressure oil circuit, the high-pressure control valve (13) regulates the flow volume to the engine oil pump (14.2), which influences its delivery rate.

Piston heating function:

During a cold start, the engine oil temperature is low, i.e., the engine oil is highly viscous. When the combustion engine is started with low oil pressure, the pistons heat up more quickly.

Oil heating function:

Following operation of the piston heating function, the engine is run for a certain time with a high oil pressure. The spray oil cooling of the piston crown activated in this way causes rapid warming of the engine oil. Therefore oil has a low viscosity quicker and the friction power in the engine drops. Thus fuel is saved directly.

Peak/hold function:

To reduce the power consumption of the oil pressure pump, the pressure regulating valve is activated by means of a peak/hold function.

The crankshaft bearings are supplied with engine oil via the oil ducts. From the crankshaft bearings, the following are components are supplied with engine oil through holes in the crankshaft:

IMPORTANT The peak/hold function is a function for saving a maximum achieved value.

The engine oil flows under gravitational force back to the oil pan (1).

In addition to the direct oil supply by the oil pressure pump, the rotational movement of the crankshaft results in fine preparation of the oil mist in the crankcase. The pistons are cooled by means of a switchable oil-spray nozzle.

  Additional basic functions     
  Oil pump valve, basic function   GF18.10-P-2000A
  Engine oil temperature sensor, basic function   GF18.30-P-2000A 
  Engine oil fill level sensor, basic function   GF18.40-P-2001A
  Component descriptions     
  Shutoff valve for oil spray nozzles, component description Engine 656 in model 223 GF18.30-P-2012A
    Engine 654 in model 206 GF18.30-P-2012C
  Engine oil pressure and temperature sensor, component description Engine 256 in model 223 GF18.40-P-4102A
    Engine 254 in model 206 Engine 654 in model 206 GF18.40-P-4102C
  Engine oil pressure sensor, component description Engine 656 in model 223 GF18.40-P-4104A
    Engine 139 in model 206 Engine 254 in model 206 GF18.40-P-4104C
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