Throttle valve
There are two throttle valves in the intake manifold. The smaller of these dampers is connected by a drive cable «gas» with a pedal in the cabin. It doses the flow of intake air into the engine. If the accelerator pedal is pressed harder, then the rod opens the second, larger flap. In the full position «gas» both dampers are open.
Combustible mixture corrector
It is the main component of the injection system and consists of an air mass meter and a fuel dispenser. They act like this:
The lightweight tin plate of the air mass meter sits in the middle of the airflow sucked in by the engine. This valve stem rises due to the suction of the pistons during the intake stroke, and the more, the more air passes from the throttle. By means of a system of levers, the disc deflection is transmitted to the fuel dispenser.
The fuel dispenser mainly consists of a control piston and a spool housing. For each cylinder of the engine, there is a slot in the spool body through which fuel enters the corresponding injection nozzle. The control piston opens or closes these slots more or less and thus - depending on the position of the valve plug - admits the appropriate amount of fuel.
System pressure
The fuel pump in the fuel tank pumps fuel under pressure to the injection system. The first instance here is the system pressure regulator in a separate housing. It reduces overpressure and leaves only 6.1 to 6.5 bar for the fuel system. This pressure, the pressure in the system, acts in the dispenser, fuel line and injection nozzles.
Pressure meter
The pressure regulator is responsible for the composition of the mixture. This happens as follows: the flow of fuel to the lower chambers (through which you can influence the amount of mixture) through the pressure regulator. If it passes a lot of fuel into the lower chambers, then pressure increases in the lower chambers. Consequence: The membranes of the so-called differential pressure valves sag towards the valve openings - less fuel reaches the injection nozzles. On the contrary, it certainly works in the same way. The desired result is achieved: the amount of fuel changes in relation to the incoming air - the mixture is enriched or depleted. The pressure regulator receives commands from the control unit. This occurs depending on the lambda control, engine temperature and engine load. The pressure sensor is located on the side of the fuel mixture regulator. Its functions should be considered in addition to the main function of the fuel mixture regulator, which is preserved in the event of an electronics failure.
Intake nozzles
As soon as the fuel pressure has reached 3.7-4.8 bar, the injectors supply gasoline to the channel in front of the valve of the corresponding cylinder. At the same time, they open up to 2000 times per second, thanks to which the gasoline is sprayed especially finely.
Control block
The control unit regulates the composition of the engine mixture through the pressure regulator. In order for this control to be based on something, the control unit receives data on engine temperature, speed, starting processes, the position of the valve shutter (from idle to full load). This adds the signal of the lambda probe, data from the ignition system, atmospheric pressure sensor (only for KE-lll-Jetronic) and from an automatic transmission. The control unit is located in the passenger compartment in the area of the front passenger's feet.
Idling stabilization control valve
Function: The valve opens the air passage around the throttle valve. The effect is as follows: due to the increased amount of air, the air mass meter «believes», that the throttle valve is slightly opened and therefore provides a correspondingly increased fuel supply. Desired result: increased rotational speed.
How much additional air is supplied is determined by the injection system control unit KE-Motronic or KE-III-Jetronic, namely in accordance with the speed at a given time. Thus, the electronics seeks to return the speed to the standard range.
Start fuel valve
This is a solenoid-actuated injector that, depending on the engine temperature at start-up, supplies an additional amount of finely atomized fuel to the intake manifold. The injection duration is determined by the injection system control unit KE-Motronic or KE-III-Jetronic.
Angle encoder
The Audi-100 has two throttle angle sensors. They signal the following data:
Idling: to control the idling speed, stop the fuel supply in the forced idle mode; fully electronic ignition system, etc.
Full throttle: to enrich the combustible mixture in full throttle mode «gas» and a fully electronic ignition system.
Left: KE-III-Jetronic injection system of a 4-cylinder engine:
1 - solenoid valve of the tank with activated carbon;
2 - valve shutter potentiometer;
3 - pressure regulator;
4 - pressure sensor;
5 - fuel dispenser.
Right: KE-Motronic injection system of the 5-cylinder engine:
1 - pressure regulator;
2 - valve shutter potentiometer;
3 - pressure sensor;
4 - fuel dispenser;
5 - air intake sleeve.
Scheme of the injection system KE-III-Jetronic or KE-Motronic. Fuel is shown in red, incoming air is highlighted in light pink.
Fuel cut (forced idle)
The already mentioned pressure regulator stops the fuel supply if the car is operated in forced idle mode. The control unit recognizes this mode by information «RPM is higher than idle RPM» And «throttle closed».
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