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piezo injector waveform and needle movement
piezo injector waveform and needle movement
Ford Focus 1,6TDCI III 2011, diesel Duratorc
Hello everyone !
I have noticed that the closing current ends just after a very small peak (I find exactly this small peak at the same place on all the recordings of the other cylinders).
Can this small peak can show the precise moment of immobilization of the needle? Or do i dream
?
Please see the black arrow on the graph and keep remind that it is piezo and not solenoide injectors.
If you have any further comments, please feel free
Greats thanks !!
Nico
Pico 2O24A
Hello everyone !
I have noticed that the closing current ends just after a very small peak (I find exactly this small peak at the same place on all the recordings of the other cylinders).
Can this small peak can show the precise moment of immobilization of the needle? Or do i dream
? Please see the black arrow on the graph and keep remind that it is piezo and not solenoide injectors.
If you have any further comments, please feel free
Greats thanks !!
Nico
Pico 2O24A
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Re: piezo injector waveform and needle movement
Up, no more ideas here ? 
Re: piezo injector waveform and needle movement
toujours pas d'idées ? 
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Steve Smith
- Pico Staff Member
- Posts: 1594
- Joined: Sun Aug 25, 2013 7:22 am
Re: piezo injector waveform and needle movement
Hello and thank you for the post, sorry for the late reply
An interesting question for sure and one where I have referred back to the operation of conventional solenoid injectors (Petrol port injectors)
The disruption we see during the ramping up of port injector current is caused by a disruption to the magnetic field about the solenoid windings as the pintle lifts off its seat and pass through the said windings. Likewise, the same event can be seen in the induced voltage as the pintle closes
With Diesel Piezo injectors, there is no mechanical link or electrical interaction between the piezo stack and the pintle of the injector. The “link” between these components is hydraulic and pintle movement is created by a differential in fluid pressure (“Fluid” being diesel)
I have then taken a look at our example waveform with the Guided Test here https://www.picoauto.com/library/automo ... o-current/ and highlighted the area you mention in your image
This would appear to be a final oscillation of discharged current dissipating into the injector circuit given the reduction in amplitude and frequency
With that said, “Never Say Never” and I sense another experiment coming on.
I would repeat this test looking at injector voltage (both sides of the injector) and current. I would then add fuel pressure and an accelerometer to the injector pipework or a listening device clamped around the body of the injector (Non magnetic of course)
Next, I would choose a high sample rate and focus on just one injection event (Pre, Pilot or Main)
Here we can observe the behavior of the common rail fuel pressure in relation to an injection event whilst monitoring voltage structure, voltage differential and injector current against vibration/sound generated during the process
From this capture we may be able to attribute events seen within the current to physical events within the injector
On a side note, for anyone curious about Piezo injectors, we have discussed their functionally in depth here topic19561.html
I hope this helps, take care……Steve
An interesting question for sure and one where I have referred back to the operation of conventional solenoid injectors (Petrol port injectors)
The disruption we see during the ramping up of port injector current is caused by a disruption to the magnetic field about the solenoid windings as the pintle lifts off its seat and pass through the said windings. Likewise, the same event can be seen in the induced voltage as the pintle closes
- Image 1
I have then taken a look at our example waveform with the Guided Test here https://www.picoauto.com/library/automo ... o-current/ and highlighted the area you mention in your image
- Image 2
With that said, “Never Say Never” and I sense another experiment coming on.
I would repeat this test looking at injector voltage (both sides of the injector) and current. I would then add fuel pressure and an accelerometer to the injector pipework or a listening device clamped around the body of the injector (Non magnetic of course)
Next, I would choose a high sample rate and focus on just one injection event (Pre, Pilot or Main)
Here we can observe the behavior of the common rail fuel pressure in relation to an injection event whilst monitoring voltage structure, voltage differential and injector current against vibration/sound generated during the process
From this capture we may be able to attribute events seen within the current to physical events within the injector
On a side note, for anyone curious about Piezo injectors, we have discussed their functionally in depth here topic19561.html
I hope this helps, take care……Steve
Re: piezo injector waveform and needle movement
Steve, it's just fascinating to read you !! 
I'm going to do this test again to see
Thanks a lot, and nice we !
I'm going to do this test again to see
Thanks a lot, and nice we !