Autoditex PPS Pressure Pulse Sensor
Since 2004 a worldwide use of the so called Pressure Pulse Sensors - PPS in automobile diagnostics started.
In normal operation of internal combustion engines pulse waves of pressure are generated in various systems. All engines produce such waves and their shape is predictable.
All engines produce a predictable pattern of these pulses so any change in shape or appearance of asymmetry of these pulses indicates a problem with the engine.
The Autoditex PPS detects such faults as burnt valves, bad injectors and other performance problems without major disassembly of the engine. To visualize the waveform of the output signal of PPS, its electrical part is connected to an oscilloscope (motortester; automotive scope). The screen will show in real time the work of valves, cylinders and injectors, and by using synchronization to the first cylinder it can be determined by its performance which cylinders has a problem. The automechanic can therefore quickly and accurately get an idea of the actual condition of the engine. Pressure Pulse Sensor does not need additional external power supply and it can be used with most modern digital storage oscilloscopes (motortester).
With this Pressure Pulse Sensor we can observe the waveform of:
• Pulsation of exhaust gases in the exhaust;
• Changes in the gas pressure in the inlet manifold;
• Fluctuations in the membrane pressure regulator of the fuel;
• Crankcase gases and other.
Included in the kit:
• 1 Piezoelectric Pressure Pulse Sensor;
• 2 m cable - BNC to BNC cable;
• 2 m hose.
This sensor can be encountered under several different names but in the end it comes to the same device.
Some of the most commonly used names are:
- Automotive Pressure Pulse Sensor (PPS);
- Intake manifold sensor.
Note: Pressure Pulse Sensor is suitable for measuring pressure fluctuations in gas only! It is not suitable for measuring fluid pressure fluctuations!
Some of the advantages of the Pressure Pulse Sensor are:
- Fast and easy connection;
- Locate cylinder problems thru the exhaust pulses; - Detect valve leakage, cylinder compression;
- Find injector problems.
Note: Pressure Pulse Sensor (PPS) doesn’t measure the static pressure. It can be used only to display the pressure changes. It’s a transducer that converts changes in the gas pressure to an electrical signal.
In internal combustion engines during normal operation, pulsating pressure waves are generated in various car systems. All engines produce such waves and their shape can be predicted. Any change in the shape or asymmetry of these pulses, indicate an engine problem.
The Pressure Pulse Sensor is unique because it looks at pulses in engine airflow, allowing you to display “engine pulse” on standard oscilloscope. Engine analyzers tell us what the ignition system or sensors are doing, but it is difficult to see what actually happens in the engine without intrusive tests. With the Pressure Pulse Sensor it is possible to see what is dynamically occurring in your engine.
With the Pressure Pulse Sensor you can now have a more complete picture of an engine’s performance, quickly and easily. Once you have learned to use the sensor combined with the timing chart you will be able to observe the real-time operation the valves, cylinders and injectors and thereby find burnt valves, bad (dirty) injectors, wrong timing and other engine performance problems without major disassembly of the engine. By using the first cylinder for synchronization, a faulty cylinder can be determined.
Engine problems will always cause a fluctuation of the waveform that extends above or below the average of the other cylinders. This is where comparative analysis of cylinders becomes important. In general the more symmetrical the waveform and distribution above and below the zero reference line, the better the condition of the engine.
Pressure Pulse Sensor does not need an external power supply and it can be used with most of the modern digital storage oscilloscopes (motor testers).
Automotive pressure pulse sensor
With this sensor you can also determine the degree of contamination of the injectors without having them dismantled. For this purpose, the pulse sensor must be connected to the fuel pressure vacuum regulator.
This method can only be applied to systems with sequential injection, and cannot be used in systems with double-parallel and parallel-injection.
In the fuel injection system, fuel pressure is maintained relatively constant with the help of the fuel pressure regulator. It maintains a constant pressure by returning part of the fuel back in the fuel tank. Operation principle is based on a membrane which on one side is pushed by a tarred spring and from the other side is applied the fuel pressure.
Once the fuel pressure exceeds the force of the spring, membrane diaphragm moves and opens the valve to return the fuel in the tank, which reduces the fuel pressure. Thus, the pressure is maintained at a normal operating value. When injector opens part of the fuel passes through it, which leads to reduction of the pressure in the fuel rail. The membrane of the pressure regulator inclines in the other direction and thus closing the return valve partly and thus compensating the fuel pressure. This process requires some time. By how much the membrane has been moved to compensate the fuel pressure reduction at the opening of the injectors depends on the amount of fuel passed through the injector. When the injector closes the reverse process begins, the membrane is tilted in the opposite direction to compensate the emerging high pressure that enters the fuel pump.
These constant fluctuations of the membrane during normal engine operation can be displayed on the oscilloscope screen.
Pressure Pulse Sensor intake manifold pulses and the crankshaft signal: Point’s description: 1. Opening of the 4th cylinder intake valve; 2. Closing of the 4th cylinder exhaust valve; 3. Opening of the 2ndcylinder intake valve; 4. Top dead center (TDC) point; 5. Closing of the 2nd cylinder exhaust valve; 6. Opening of the 1st cylinder intake valve; 7. Closing of the 1st cylinder exhaust valve; 8. Opening of the 3dcylinder intake valve; 9. Closing of the 3d cylinder exhaust valve; 10. At this point the first cylinder pulse occurs.
DITEX PRESSURE PULSE SENSOR
Min. Pressure 0.2 bar (-0.8 bar in vacuum)
Pressure connector 6mm (1/4 inch) bronze hose nozzle
* Conversion rate means how fast the input pressure is converted to an output electrical signal.
Note: Ditex Pressure Pulse Sensor is suitable for measuring pressure fluctuations in gas only! It is not suitable for measuring fluid pressure fluctuations!
Note: Ditex Pressure Pulse Sensor (PPS) doesn’t measure the static pressure. It can be used only to display the pressure changes. It’s a transducer that converts changes in the gas pressure to an electrical signal.
Max. Pressure 4.5 bar absolute pressure (3.5 bar atmospheric pressure)
Minimum conversion rate* 1 Hz
Maximum conversion rate* 5000 Hz
Output signal type Voltage pulses
Output range ±0.5V; ±1V; ±2V; ±5V; ±10V
Power supply Not needed
Electrical connector BNC 50 ohm connector for RG58 cable
Weight (main unit) Approximately 0.1 kg
Weight (basic set) Approximately 0.4 kg