With the use of electronic management in both gasoline engines and in diesel, the regulatory control of turbo boost pressure is no longer leaves the hands of a valve actuation as a mechanical valve is the wastegate, which is subjected to high temperatures, and components such as spring and membrane deformations suffering and distress that affect a poor control of turbo boost pressure, and not taking into account factors as important for the proper functioning of the engine as the altitude and temperature.
To describe how a system for regulating the pressure of the turbo, we have a diagram (figure below) that belongs to a diesel engine (1.9 TDI) in which one sees all the elements involved in controlling the pressure of the turbo. The electronic management Diesel (EDC Electronic Diesel Control) interposes a pressure control valve (3) between the intake manifold and waste gate valve (4) which controls all the time pressure that reaches the wastegate valve. As seen in the control circuitry of the turbo pressure is similar to a conventional control loop the only difference being the incorporation of the control valve (3).
The main characteristics of this system are:
- Allows the maximum pressure turbo.
- Has cut injection at high speeds.
- Provides a good response to the accelerator throughout the margin of rotations.
- The speed of the turbo-compressor can go up to 110,000 rpm
The solenoid control (AMAL) behaves as a "passkey" that lets through more or less pressure to the wastegate valve. This is controlled by the ECU (control unit) that causes the electrical impulses through the opening or closing. When the engine rotates at low and medium speeds, the valve control misses the pressure that is in the intake manifold through its entrance (a) until the exit (2) and directly to the wastegate valve, whose membrane is pushed to cause its opening, but this does not take effect until the blowing pressure of the turbo is enough to overcome the spring force. When the engine revs are high pressure that reaches the wastegate valve is very high, enough to overcome the force of its spring and open the valve to derive the exhaust gas bypass the (low pressure turbo). When the ECU believes that the pressure in the intake manifold may exceed the normal operating margins, either by circular altitude, high ambient temperature or by a request from the driver of high performance (hard acceleration and sudden), without this jeopardize the smooth operation of the engine, the ECU can modify the value of the pressure that comes with the turbo wastegate valve, cutting off the passing of pressure through the control valve closes the passage (1) and opens the way (2) (3), thus calling into contact with the waste gate valve to atmospheric pressure that will keep closed and thus increases the pressure of the turbo.
To be clear, what does the solenoid control during operation, is to deceive the wastegate valve diverting part of the turbo pressure to prevent it from acting.
The valve control is managed by the ECU (control unit), linking the mass of its electrical terminals with a fixed frequency, where the amplitude of the signal determines when to open the valve to increase pressure of the turbo manifold. The ECU to calculate when to open or close the valve control takes into account the pressure in the intake manifold through the turbo pressure sensor that is embedded in the ECU itself (figure p.9) and that receives the pressure via a tube (7) connected to the intake manifold. Also takes into account the air temperature in the intake manifold through a temperature sensor (6), the number of engine rpm and altitude by means of a sensor that is sometimes embedded in the ECU or outside.
As we outline below the inlet and exhaust of a diesel direct injection (TDi) that uses a turbo-compressor geometry (TGV). As shown in the diagram does not show the wastegate or wastegate and even though the solenoid control pressure turbo (3) is still present and it leaves a tube that goes directly to the turbo-compressor. Still not seeing where it binds specifically, the tube is connected to the valve or actuator. The operation of the turbo pressure control is very similar to previously studied, the difference is that the wastegate valve is replaced by a vacuum valve, both have a similar operation, while an open or close a valve, the other moves a mechanism vane actuator.
In this case the altitude sensor is out of the ECU (control unit).
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