Function

Function

Oil pan
The main task of the oil pan is to be the reservoir for the oil. It is also part of the cylinder block. There are a number of components which are secured in or on the oil pan.
The oil level is checked via the dipstick which is connected to the oil pan. A suction pipe with a nozzle supplies the oil pump with oil which is then pumped onwards in the engine. To facilitate the suction function of the oil pump, there is a bleed valve which ensures that any air in the system is evacuated. The oil flows through the oil cooler to lower its temperature. The oil cooler is screwed to the outside of the oil pan.

Crankshaft




The function of the crankshaft is to transfer the upwards and downwards power of the piston movement. The engine is pendulum mounted, which provides better crankshaft balance than a non-pendulum mounted engine. The connecting rod, which is secured on the crankshaft, transfers the upwards and downwards movement of the piston into crankshaft rotation.

Piston
The main task of the piston is to compress the fuel/air mixture during the different strokes. The piston rings provide a seal so that the fuel/air mixture is not forced past the piston. The uppermost ring expands when the piston moves downwards. The second ring, as well as sealing is an oil scraper ring during the downward piston movement. The third ring ensures that the oil is drained via the drainage hole.

Camshafts, valve system




The camshafts and valves let in the fuel/air mixture for the ignition stage. The camshafts and valves then release the fuel/air mixture after ignition.
Conical valve springs allow smaller shims to be used and reduce the total moving mass. The valve springs operate progressively. This means that there is little force at the beginning and the end of the closing phase, but considerable force during maximum valve lift.
The camshaft is rotated by the timing belt which is turned by the crankshaft. When the cam lobes on the camshaft press in the valve lifter, the valve is also pressed in and lets the fuel/air mixture out. A VVT unit on the camshaft can vary the valve timing steplessly using the oil pressure. The function of the VVT unit is to determine when to open or close the valves (within specific tolerances).

Mechanical belt tensioner




The belt tensioner must maintain constant pressure on the timing belt and prevent the belt from jumping off the cogs.

Lubrication system




The oil is led from the oil pan via a suction piece to the oil pump. The oil pump is located on the cylinder block. The oil is then pumped onwards to the oil cooling system and then to the oil filter.
The oil flows from the filter through a cast oil duct in the intermediate section to the main bearings. The oil then flows through bored channels in the crankshaft to the connecting rod bearings. The camshafts are supplied with oil by a bored channel in the cylinder block. The channel runs through the cylinder head, where it flows out at the bottom of the upper half of the cylinder head. There is a cross duct in the channel to the cylinder head which carries oil to the pistons via a piston cooling valve. The oil flows on via an oil duct to the bearing for the left-hand camshaft and the valve lifters (intake side).
The bearings for the right-hand side camshaft (exhaust side) are supplied by a cast cross duct at the front edge of the upper half. This cast cross duct also supplies pressurized oil to the solenoids for the VVT unit. Drain holes in the cylinder block release the oil from the cylinder head and crankshaft bearing back to the oil pan.

Oil filter




The filter is an environment filter which filters out any dirt particles from the oil. The oil flow from the outside into the filter. If the filter becomes blocked, the by-pass valve opens so that the oil can pass the filter. This ensures that the engine is always lubricated with oil.

Piston cooling valve




The piston cooling valve regulates the oil flow by letting oil through the piston cooling nozzles.

Oil pump




The oil pump pumps oil from the oil pan via channels in the intermediate section and cylinder block into the cylinder head and onwards in the system. The oil pump is on the end of the crankshaft. The crankshaft runs through the oil pump. A duo-centric gear wheel reduces the flow of oil, increasing the pressure. This results in a pulse action which forces out the oil. The oil can only flow in one direction.

Injector
The injector ensures engine performance in certain situations. The fuel comes from the fuel rail to the inlet for the injector and then through the injectors. The fuel is mixed with the intake air. The fuel/air mixture must be as homogenous as possible.

Evaporative emission (EVAP) system









The EVAP canister absorbs the hydro-carbons in the fuel vapors so that they are not released. The engine control module (ECM) controls the EVAP valve. The hydro-carbons are emptied from the EVAP canister when the valve is open. When emptying, the atmospheric air flows through the EVAP canister (where stored hydro-carbons are gathered) and on to the intake manifold and combustion chamber. The energy in the hydro-carbons is then used during the combustion process. So that emissions are not negatively affected, the EVAP valve is pulsed by a pulse width modulation (PWM) signal, the frequency of which is calculated by the engine control module (ECM).
The signals from the heated oxygen sensors (HO2S) are used as a reference. The EVAP valve is closed during the leak diagnostic. The leak diagnostic unit checks the gas and fuel filled sections of the EVAP system. Any leaks in the fluid filled sections cannot be detected. When the pump is not activated, it is open so that the fuel tank and EVAP system can "breathe".
A number of parameters must be met before the EVAP canister can be emptied. For example:
- the engine coolant has reached a certain temperature.
- the fuel/air ratio is within the tolerance zones.
During leak diagnostics, the control module activates the pump and test pressurizes/calibrates the pump against a built-in leak scenario in the pump module. A valve then closes so that the pump motor can create overpressure in the tank and EVAP system. The control module is able to determine the size of the leak in the tank and EVAP system by measuring the power consumption of the pump in these two circumstances. If the current level is too low in relation to the level for the in-built leak scenario, there is leakage in the system. The built-in PTC heater element is used to prevent condensation in damp weather which could disrupt the leak diagnostic.

Intake system
Each cylinder has an intake manifold which comes from a plenum chamber. The injectors are on the lower aluminum intake manifold close to the intake valves. This is so that the fuel mixes as well as possible with the turbulent air. The position of the injectors is optimized to minimize wetting the cylinder walls and therefore emissions. There are ducts in the lower intake manifold for the crankcase gases so that they can reach the combustion chamber.





For B5xx4Sx
The air enters via the air intake on the front member. The air is routed via a cold air hose in the air cleaner (ACL) housing. Here there is also a snow valve. This valve opens if the air cleaner (ACL) housing and air intake are blocked by snow. This lets the air flow through and also uses cooling flanges to cool the engine control module (ECM). The air then flows through a funnel with a net which reduces air turbulence before the air reaches the mass air flow (MAF) sensor.
The mass air flow (MAF) sensor controls the mass air flow to the engine. The air then flows to the electrical throttle body (TB) and into the intake manifold. The manifold absolute pressure (MAP) sensor gauges the pressure in the intake manifold. The evaporative emission system (EVAP) valve recirculates the fuel/air mixtures for further combustion. The evaporative emission system (EVAP) valve is by the throttle body (TB). There is a direct terminal from the air cleaner (ACL) to the intake manifold which by-passes the mass air flow (MAF) sensor. There is a brake vacuum ejector in the middle of the hose. The brake vacuum ejector uses the pressure differences in the air cleaner (ACL) housing and plenum chamber to create a flow in the hose to create a vacuum in the brake booster.





For B5xx4Tx
The air enters via the air intake on the front member. There is a rail in the air intake pipe which divides the pipe to minimize drops in pressure. The air then flows on to the air cleaner (ACL) housing. Here there is also a snow valve. This valve opens if the air cleaner (ACL) housing and air intake are blocked by snow. This lets the air flow through and also uses cooling flanges to cool the engine control module (ECM).
The air then flows through a funnel to the mass air flow (MAF) sensor. The mass air flow (MAF) sensor controls the mass air flow to the engine. The air then flows through a fresh air hose over the engine. The air then passes the turbocharger (TC) and charge air cooler before reaching the electronic throttle body (TB) and being released into the intake manifold. The evaporative emission system (EVAP) valve recirculates the fuel/air mixtures for further combustion. The evaporative emission system (EVAP) valve is by the throttle body (TB).

Throttle body (TB)
The throttle body guides the air flow into the intake manifold. The requested throttle disc angle is obtained by the driver by the accelerator pedal movement / accelerator pedal position. The intake air comes from the air filter housing through the throttle body and on to the intake manifold.

Turbocharger (TC)
The exhaust gases enter the turbine housing via the manifold and then flow out to the exhaust system via the down pipe and three-way catalytic converter (TWC). The turbine expels the exhausts and rotates the compressor wheel. The compressor wheel creates a certain amount of suction using the intake air. This intake air enters the compressor via the air filter and uses a rotational movement to speed up the air, creating the boost pressure.
The air then continues into the intake system. The wastegate valve then controls the boost pressure in the turbocharger by determining the amount of exhaust gases which must pass the turbine to transfer drive to the compressor. The by-pass valve is a membrane which equalizes the pressure of the intake and exhaust air to eliminate noise.

Exhaust system
The three-way catalytic converter (TWC) acts by oxidizing carbon monoxide (CO) and hydro-carbons (HC) to water and carbon dioxide (CO2). Nitrous oxides (NOx) are reduced to nitrogen and water. Over 98% of these substances are converted in the three-way catalytic converter (TWC) during normal driving. Lead pollutants in the fuel damage the three-way catalytic converter (TWC) and can quickly render it unusable.

Crankcase ventilation
The crankcase ventilation controls the pressure in the crankcase. The crankcase gases are also separated in the flame trap and cyclone separators and favorable particles are returned to the engine.

Flame trap
The flame trap roughly separates the crankcase gases from the cylinder block. The crankcase gases circulate around the walls in the flame trap before entering the cyclone separators. The cyclone separators act on the crankcase gases to separate the particles/substances. The oil in the crankcase gas runs down into a container chamber to be returned to the oil pan. The rest of the crankcase gas is directed on to a pressure regulator which regulates the pressure in the crankcase. The crankcase gas is then evacuated from the pressure regulator to return to the intake manifold via the turbocharger on vehicles with turbocharged engines. Otherwise the gas returns directly to the intake manifold.

Radiator
When the coolant temperature is high enough to partially open the thermostat, the coolant is distributed via the radiator and the bypass channel to the coolant pump. When the thermostat is fully open, all the coolant goes to the radiator. The cooled air is sucked through the radiator by an electric engine cooling fan (FC) on the fan shroud behind the radiator.

Thermostat
The thermostat regulates the amount of coolant to the engine. The wax body expands when energy reaches it in the form of heat. In modern cooling systems, the thermostat begins to expand when the surrounding coolant temperature is 90 °C.
When the wax body expands in the thermostat, a flow of coolant is allowed through the radiator whilst the flow to the by-pass is shut off to speed up cooling. Coolant routed through the bypass returns to the engine without being cooled. Any air is able to leave the system via a jiggle pin. The jiggle pin is in the thermostat.