The basic, classic model, the K-Jetronic system, is completely mechanical and operates on the principle: a large amount of intake air - a large amount of fuel. However, the use of lambda zones yes for a variable catalyst on engines with this injection system was not possible without additional equipment. This, in fact, was the motivating reason for the further improvement of K-Jetronic.
The main components of the system were retained, but were supplemented by an electronic control unit and the so-called air-fuel mixture corrector - an electrical actuating element that additionally regulates the fuel supply. This corrector is usually included in the work when the engine warms up, but at the same time it performs its main function regarding the composition of the air-fuel mixture.
Together with a fully electronic ignition system, this injection system is an engine control unit. Despite the fact that both of these systems have their own control units, the exchange of information between them occurs constantly. In addition, the information needed for ignition and for fuel injection comes from the same sensors. A self-diagnostic system with a memory of failures that have occurred completes the list of electronic innovations introduced to the base model (see illustration 11.0).
Main components of the system
Throttle valves
In the intake manifold, there are two throttle valves on one pipe. The smaller of these shutters is connected by a cable «gas» with accelerator pedal (see illustration 11a).
Until the accelerator pedal reaches the position «Full throttle», this flap regulates intake air metering. And only when the accelerator pedal is sufficiently depressed, the corresponding rod opens the second flap of a larger diameter.
Air-fuel mixture regulator
It is the main component of this fuel injection system. It consists of an intake air volume flow meter and a fuel distributor (see illustration 11.0b).
The principle of its operation is as follows. The shut-off damper for the air flow meter, made of light metal, is located in the path of the incoming air flow. Under the pressure of the air flow, it opens. Its opening angle is greater, the more air enters through the throttle. Through a system of levers, the deflection of the gate valve is communicated to the fuel distributor (see illustration 11.0c).
The damper should be lower by a = 1.9 mm from the top of the narrow edge of the funnel. If necessary, the damper position can be corrected by bending the spring (see illustration 11.0c).
Attention! The newer types of air mass meters have an adjusting screw instead of a spring, allowing for more precise adjustments.
The main parts of the fuel distributor are the distributor piston and the cylinder window through which the fuel enters the injector. The control piston closes or opens this window and admits fuel in proportion to the degree of deflection of the air flow meter gate valve.
Fuel pressure in the system
The fuel pump in the fuel tank delivers pressurized fuel to the injection system. On the way of the fuel flow there is a fuel pressure reducing valve installed in the housing. This valve removes excess pressure, leaving a pressure of 6.1-6.5 bar in the system.
Differential air-fuel mixture corrector
The corrector is responsible for the ratio of air and fuel in the air-fuel mixture. The corrector works as follows. The fuel flow to the lower chambers, from which the composition of the mixture can be adjusted, passes through the corrector. Accumulating in the lower chambers, the incoming fuel creates a certain pressure there. The strength of this pressure depends, in turn, on the volume of fuel passed by the corrector. The corrector membrane reacts to the pressure drop by deflecting towards the holes through which the fuel enters the nozzle, blocking it to a greater or lesser extent. Thus, less or more fuel is supplied to the injectors, providing the desired composition of the air-fuel mixture.
Relevant «instructions» The air-fuel mixture corrector receives from the control unit, which responds appropriately to information from the lambda probe, the coolant temperature sensor and, in general, to the operating load on the engine.
The air-fuel ratio adjuster is located on the side of the mixture ratio regulator. The corrector is an additional element of the functioning of the regulator, which continues to work even if the electronics fail.
nozzles
The injectors inject fuel into the intake port before the intake valve of the corresponding cylinder as soon as the fuel pressure rises to 4.3-4.6 bar. The nozzles open up to 2000 times per second, providing a high degree of fuel atomization.
Electronic control unit
The electronic control unit of the system, through the corrector of the composition of the air-fuel mixture, provides the mixture composition that the engine needs at the current moment. To control this process, the unit needs information about the engine temperature, the number of revolutions, the conditions for starting the engine, the position of the shut-off valve of the air flow meter, the engine operating mode (idle, full load). This information is supplemented by the corresponding signals from the lambda probe, as well as additional information from the ignition system, altitude corrector and automatic transmission. The electronic control unit, like all other AUDI 80 models, is located in the passenger compartment, on the right side, between the air supply duct from the heater and the dividing wall between the passenger compartment and the engine compartment.
Idle stabilization valve
This valve opens a passage for air to bypass the throttle body. The essence of this approach is as follows. Intake air flow meter «believes», that the air volume has increased as a result of the throttle opening and provides a corresponding increase in injected fuel. The result is an increase in engine speed. The volume of additional intake air is determined by the control unit of the KE-III-Jetronic system, based on the number of engine revolutions at the current moment. Thus, the electronics seeks to bring the engine speed to nominal values.
Start fuel valve
The starting fuel solenoid valve is a nozzle that, when the engine is started, depending on its temperature, briefly injects fuel into the intake manifold, spraying it at the same time. The duration of the injection is set by the control unit of the KE-III-Jetronic system.
Throttle Angle Sensor
AUDI 80 vehicles are equipped with two throttle angle sensors. These sensors provide the following information:
- Idle mode. Idle control, forced idling, operation of a fully electronic ignition system in this mode, etc.
- Full load. Enrichment of the air-fuel mixture and the operation of a fully electronic ignition system.
Forced idle mode
When driving in this mode, the mentioned corrector of the composition of the air-fuel mixture shuts off the fuel supply. The electronic control unit recognizes this driving mode by the information that the engine speed is greater than the idle speed, and also that the throttle is closed.
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