Engine Lubrication, Basic Function - GF18.00-P-1003A
Engine All (4xWD)
Engine All (CAR)
Overview
This document contains information on:
- General
- Function requirements
- Function
- Wet-sump lubrication
- Oil-pressure regulation
- Dry-sump lubrication
General
The engine lubrication system basically does the following:
- Lubrication of the internal engine component parts
- Cooling (heat dissipation)
- Fine rod seal
- Engine cleaning
- it protects against corrosion
- Power transmission
Primary objective of engine lubrication is to minimize the wear of the friction partners. Engine lubrication takes place through engine oil.
Function requirements
- Engine management ON (circuit 87M)
- Engine in operation
Function
Wet-sump lubrication
Wet-sump lubrication covers the following lubrication types:
- Injection oil lubrication
- Oil mist lubrication
- Splash oil lubrication
The oil pressure pump sucks the engine oil from the oil pan under the crank assembly and pumps it under pressure to the following components:
- Oil filter
- Engine oil heat exchanger
- Oil ducts in cylinder head and crankcase
The oil pan has the following functions:
- Engine oil cooling
- Defoaming the engine oil
- Container for the engine oil
The oil filter prevents combustion residue, metal abrasion and dust from getting into the oil. The engine oil heat exchanger is connected to the cooling circuit; and is primarily responsible for cooling the engine oil.
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.
Oil-pressure regulation
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 channel or oil pan. 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. This lowers the power loss of the engine oil pumps and the resulting power loss of the engine.
The oil pressure switch is used for permanently monitoring the lubrication system. The response pressure of the oil pressure switch is generally between 2 and 4 bar.
The pressure regulating valve is actuated in a map-dependent manner with a ground signal from the motor control module and regulates the engine oil flow volume. The two compression stages 2 and 4 bar are switched between in a demand-dependent manner.
To achieve the greatest possible fuel savings, the pressure switchover now includes the following functions:
- The piston heating function
- The oil heating function
- Peak/hold function
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.
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. This helps to save fuel.
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:
The peak/hold function is a function for saving a maximum achieved value.
- Big connecting-rod bearings
- Small connecting-rod bearings in the piston
- Connecting rod
The engine oil flows under gravitational force back to the oil pan.
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.
Dry-sump lubrication
Wet-sump lubrication covers the following components:
- Oil sensor
- Oil pressure pump
- External oil reservoir
The oil pan is replaced by an external oil reservoir, 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:
- Gradients
- Extreme cornering
- Acceleration and deceleration
Dry-sump lubrication has the following benefits:
- No air is sucked in when the vehicle is cornering rapidly or when driving up/down steep gradients or at an angle on off-road areas.
- Space is saved due to the lack of a relatively large oil pan, which would otherwise be required, reduces the height of the engine.
- The oil container can be positioned anywhere and used for oil cooling.
- The oil can be cooled by the oil cooler on the way from the extraction pump to the oil container and can be cleaned by the oil filter.
| 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 | ||
| Detailed information | |||
| Engine lubrication, detailed information | Engine 256 | GF18.00-P-1101A | |
| Engine 254 | GF18.00-P-1101B | ||
| 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 |