Using the Microphone with the Pico NVH
The above vehicle was towed into the shop today with the complaint that the engine is noisey. Yes indeed this was a noisy engine with some very odd rhythms. I have the Picoscope with NVH and I’ve been looking for a reason to use the microphone and that time came today.
Check out this short recording
Here’s a zoomed in capture where I have #1 injector triggered via channel D. I figured that there were noises associated with the firing of cylinders 3 & 6. You can see in the video where these noises cycled in and out. What do you all hear besides It needing an engine?
I am not sure what I should be hearing. Is there a rattle type noise along with the knocking?
I am very interested in having a good technique to reasonably pinpoint a noise source prior to disassembly.
There are two distinct noises, one that fades in and out and the other seems to appear. Channels A/B/C are stacked on top of each other which come from the NVH module with the microphone sensor attached. I doubt that we'll be taking this one apart but this is part of why I wanted to have a look.
Scott - sounds terrible. Might be interesting to see and hear same test with cylinders 3 & 6 deactivated.
Another simple question - 2nd in 24 hours! This question is pertaining to your pattern from channel D with #1 injector events. Specifically referring to the smaller spikes you've marked as the 6 cylinders in their firing order on the same channel; are these the spikes from COP events coupled into the injector waveform via their connections at the PGM relay / power distribution bus bar common with the injector's power feed? If so it looks like a very efficient method of getting a sync from each cylinder. Excuse my ignorance - my goal for 2019 is to increase my scope knowledge so your answer will be one step in that direction!
I didn't study a wiring diagram for power distribution on this vehicle yet, however, when I saw the spikes I assumed that they were secondary hits which provided me with an additional point of reference.
Very cool scott, ive done similar with GM knock sensors, ill see if can remember to post a pic of my setup. One question, why use the injector signal as a reference mark?