I often get asked how PicoScope can be used to tackle waste spark distributorless ignition secondary analysis.
PicoScope is not an engine analyzer and does not have raster and superimposed views, nor does it come with an octopus for DIS applications. I have found that the important information in the secondary is in the detail, rather than trying to get them all on the screen at once. I like to focus on one coil at a time and take a close look. This is where PicoScope will outperform the rest. Detail.
Quickly reviewing waste spark systems, the voltage is pumped from one plug to the other so that one fires side to center electrode and the other center to side on each coil. The plugs fire in companion cylinders alternating exhaust and compression event firings. The plug under compression has a higher firing KV than the one with no pressure on exhaust. The exhaust plug fires first, followed by the compression plug a few millionths of a second later. A lot of information can be gathered by observing these events simultaneously.
Lets just look at one single capture from a Subaru:
Here, channel A is on compression and B exhaust. Note the detail in the spark line and how the firing line KV is actually displayed. We have used the two included secondary pickups and selected ranges that make then both appear 'right side up'. Remember they fire with opposite polarity. Here the firing events appear simultaneous and the firing KV and spark time look pretty good. How about if we take a closer look? With over 15,000 voltage samples on each channel here there is a lot of detail yet to be examined.
Here we have zoomed in on the capture 100x and scrolled to the firing line area. Note the exhaust firing occurs a little over 9 millionths of a second before the compression firing, as shown by the cursors (9327ns). Our rotor notch is at almost 9KV. But DIS don't have rotors! We have a gap in the secondary after the pickup on the channel A side. Not enough to raise the firing KV but surely adding resistance to the secondary flow and using up energy which shortens spark time.
Just try to do that with brand X.