Hello again and thank you for all the input and feedback.
It would be good to see other tests posted here as we can start to pick the bones out of how different spill formations vary from vehicle to vehicle.
Returning to the vehicle in my original post, we decided not only to introduce a misfire but to monitor the hydraulic activity inside No.1 injector pipe using an accelerometer.
Here we could now monitor the relationship between activities within the back leakage circuit, common rail and No.1 injector pipe, whilst utilising No.1 injector as a sync.
The results are compelling and make for interesting assumptions when analysing spill pressure.
During our analysis we did notice how the spill peak of No.4 Injector could present an issue in the near future given the odd peak formation that was not present on our original test. (Remember this is the same vehicle revisited for further testing)
Moving onto the pressure events themselves, we can see how each activity relates to another as we would appear to have all avenues covered.
The image below displays our vehicle with a misfire on No.3 Cylinder. (Injector harness disconnected and installed into a load box).
The effect of the induced voltage into the common rail pressure signal is immediately apparent with a reduction in the peak voltage during the injection event, accompanied with a disruption to the formation of the pulsations, given No.3 injector is no longer dispensing.
Moving onto the spill waveform, the initial opening of injectors No.1 and No.2 is met with an increase in spill pressure as expected.
What is interesting, the initial opening of N. 4 injector is not met with an increase in spill, which may tie up with the odd peaks we can see after No.4 injection event. (Another possible early warning for No.4 injector)
If the events surrounding No.4 injector were interesting, the fact we have an increase in spill pressure during the initial opening of No.3 injector is just plain odd, given No. 3 injector is not connected! Any theories are more than welcome here?
(Possible spill weep via No.3 injector given the rail pressure has not dropped during the missing No.3 injection event)
Finally, the accelerometer mounted on No.1 injector pipe (High pressure) reveals activity during and after the injection event along with other events from neighbouring injectors.
Remember, although the accelerometer is sensing events in No.1 injector pipe, this same pipe is connected to the common rail, so allowing the accelerometer to sense all events linked to all injection pulsations with an increased amplitude for events in No.1 injector pipe (Simply because of the mounting point of the accelerometer)
What we can conclude from the attached image is as follows: (No.1 injector only)
1. The Initial opening of the injector is met with an induced voltage into the fuel rail pressure sensor signal accompanied with a decrease in common rail pressure.
2. The initial opening of the injector is met with an increase in spill pressure followed by a drop, then an immediate peak relevant to the recovery of common rail pressure after injection (See 3 below). Therefore the large peaks we see in the spill rail occur after injection (between injection events)
3. Activity seen by the accelerometer indicate large pulsations after the injection event. As the pulsations subside, the spill pressure reaches its peak.
I hope this information is of some value and can be compared against other vehicles which I have no doubt will differ from system to system.
The use of the accelerometer in this test has highlighted the use of yet another non-intrusive technique when making an initial assessment during the golden hour!