Pressure Sensorsin the intake manifold and intake air temperature are located in their own housing, which is attached to the intake manifold. Both sensors provide the engine control unit with signals about the current engine load condition. Based on these signals, the cyclic fuel supply is calculated. The FSI engine with a displacement of 1.4 liters has a second intake air temperature sensor in the intake duct in the top cover of the engine. In addition to this, an ambient pressure sensor is located in the engine control unit.
Lambda probe (oxygen sensor) serves to control the catalytic converter. It measures the oxygen content in the exhaust gas stream and sends a corresponding signal to the engine control unit. As a rule, 2 oxygen sensors are installed. Based on the signals of the second oxygen sensor, located after the catalytic converter, the functioning of the catalytic converter is checked.
knock sensorscrewed into the engine block from the side. Its task is to prevent dangerous detonation combustion. Thanks to the sensor signals, the ignition timing is set close to the detonation combustion limit, which makes it possible to more fully use the energy of fuel combustion and reduce its consumption.
Electrically connected accelerator pedal
Instead of the usual thrust on the accelerator pedal, there is a sensor that transmits a signal to the engine control unit about the instantaneous position of the pedal. Based on this signal, the control unit changes the position of the throttle valve via an electric actuator.
Accelerator pedal position sensorlocated in the driver's footwell directly on the splined shaft of the accelerator pedal. For safety reasons, this sensor, like the throttle position sensor, provides an additional reference signal to the control unit.
In the accelerator pedal position sensor housing, there are 2 contact potentiometers mounted on a common shaft. With each change in the position of the pedal, the resistance of the contact potentiometers and the electrical voltages that are transmitted to the engine control unit change.
1 - accelerator pedal
2 - contact track
3 - sensor 1+2
If one sensor fails, the electrical communication malfunction indicator lights up, and the malfunction code is recorded in a memory device. If both sensors fail, then the engine runs at an increased idling speed and no longer responds to a change in the position of the accelerator pedal.
Throttle control unit
The throttle valve is located in the central control unit, which performs various functions. The main task of the control unit is to stabilize the idle speed of the crankshaft, regardless of the engine load by auxiliary units, such as, for example, power steering or air conditioning compressor.
1 - throttle body
2 - throttle actuator (actuating mechanism)
3 - housing cover with built-in electronics
4 - throttle valve
5 - throttle potentiometer (angle sensor 1+2 for throttle actuator)
6 - gear with spring return to its original position
Throttle actuatorconsists of an executive electric motor and a gear system with a return spring to its original position. It controls the throttle position. This ensures that the idling speed always remains the same, regardless of whether accessories such as power steering or air conditioning compressor are turned on.
Throttle position sensorlocated on the throttle shaft. It sends signals to the control unit about the instantaneous value of the angle of inclination of the throttle valve. The second potentiometer transmits a reference signal to the control unit and generates a replacement signal when the throttle position sensor fails.
Only 1.4l FSI engine with 63kW (86 hp)
For FSI engine (with layered mixing) fuel is not injected into the intake manifold, but directly into the cylinder.
While conventional gasoline engines run on a homogeneous air-fuel mixture, gasoline direct injection engines at partial loads can operate with a large excess of air due to directional charge separation. As a result, at partial loads (up to a speed of approximately 70 km/h) gasoline consumption is reduced. Thus, with layer-by-layer mixing (abbreviated FSI for short) two main methods are implemented: the method with layered mixture formation at partial loads and the method of homogeneous mixture formation at full loads. The stratified mixing technique requires an expensive engine control system. In addition, the cost of such an engine is substantially higher than that of a conventional gasoline engine.
For example, the inlet channel is double-flow. In stratification, the intake manifold flap closes the lower intake port so that the intake air is accelerated in the upper intake port and flows into the cylinder as a cylindrical flow. Additionally, the flow is accelerated by the concavity of the piston crown. During the compression stroke, shortly before the ignition point, the high-pressure fuel (50-100 bar) injected directly into the cylinder.
The fuel supply system has a low pressure circuit and a high pressure circuit. In the low pressure circuit, an electric pump with a pressure of approx. 4 bar (no more than 5 bar when starting a hot and cold engine) delivers fuel through the fuel filter to the high pressure pump. In the high pressure circuit, fuel is supplied from the high pressure pump at a pressure of 50-1100 bar to the fuel manifold (Common-Rail) and from there it goes to four high-pressure solenoid nozzles.
Since in the case of layer-by-layer mixture formation during combustion, due to excess air, the formation of nitrogen oxides sharply increases (NOx), a NOx storage catalytic converter is required in addition to the three-way catalytic converter. The design of the NOx catalytic converter corresponds to a three-way catalytic converter. However, its working surfaces are additionally coated with barium oxide, due to which nitrogen oxides at temperatures of 250°-500°can accumulate in it as a result of the intermediate formation of nitrates. The accumulation capacity, however, is limited, therefore, immediately before reaching the saturation limit, switching from layered mixing to homogeneous is carried out in order to allow the accumulated product to burn out freely.
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