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

Engine All (Light transporter)

Overview

This document contains information on:

General
Function requirements
Function

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.

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.

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

The oil heating function
The piston heating function
Peak/hold function

The 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.

The 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.

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.
Saves space because 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.

	Components
	Oil pump valve, basic function		GF18.10-S-2000A
	Engine oil fill level sensor, basic function		GF18.40-S-2001A