A PDA system is being used for the first time in Opel petrol engines in the Z 16 XEP-engine. The abbreviation PDA stands for port deactivation.
Advantages from the Use of the Pda-System
- Increase in the EGR-rate
- Extension of the speed range compatible with EGR
- Acceleration of the combustion process in the EGR-free low load range
- Improvement of smooth-running in the part load range because of high charge carrier mobility
- Reduction of fuel consumption
Mode of Operation of the Pda-System
- Closing one of the two intake ports per cylinder respectively leads to an increase in charge carrier mobility and therefore to rapid and stable ignition, thus providing the pre-condition for a high EGR-rate.
- The use of exhaust gas recirculation then reduces the high combustion speed again to the point where the best possible compromise is reached with regard to combustion noise, untreated exhaust emissions, the knock limit and charge changing losses.
- As a result, this produces a reduction in untreated exhaust emissions and a clear saving on fuel.
- 1. Vacuum unit
- 2. Injection valve
- 3. Switching valve
- 4. Inlet valves
Mode of Operation of the Pda-System
- The switching valves, each positioned in the so-called filling port, are opened or closed by a shared actuating rod via a vacuum unit. To do this, the intake pipe has an integrated reservoir which permits a small number of switching operations even if the intake pipe vacuum is slight.
- After starting the engine, a sufficient vacuum is normally present within a few seconds to trigger the actuating valve via the engine control unit. When not triggered, the valve opens by spring force, the vacuum unit is ventilated and the valves are opened by restoring springs in the vacuum unit and in the position sensor.
- Engine control functions, which are dependent on the valve position, such as the EGR-rate and ignition are controlled via the position sensor dependent on the actual position of the switching valves.
- The injection of the fuel takes place via new 2-jet injection valves, whereby one jet respectively supplies the filling and the swirl port.
- To ensure that the switched off ports are flushed out, the switching valves have a slight defined leakage - the filling ports are therefore never completely closed.
- Closing the switching valve is always demanded by the engine control unit when this will result in advantages with regard to fuel consumption and smooth-running which is generally the case when idling and in the part load range up to about half load and a speed of approx. 3000 rpm. As a consequence of this, the mixture drawn in mainly only flows through the port designed for swirl.
- With the switching valve open, i.e. during full load and at high speeds, the mixture also flows through the second port, designed for optimum filling.
- 1. Vacuum unit
- 2. Actuating rod
- 3. Position sensor
- 4. Switching valves
Pda-System Diagnosis
- By the determination of the actual valve position via the position sensor, the vehicle can still be driven without significant restrictions even if malfunctions may have arisen in the switching valve sector.
- Therefore, possible customer complaints would be lack of smooth-running during idling or at part load with the valves stuck open or lack of performance at high speed with the valves stuck closed.
- Switching valve faults are collected by the engine control unit via the position sensor and stored in the fault memory.
- These can then be read off with TECH 2.