aussiechris Posted February 27 Author Report Share Posted February 27 Just a quick update to my original post... I've purchased a more modern 4 channel oscilloscope to replace my old 2 channel unit. This allows me to simultaneously display the relationship between crank sensor, fuel injection, and ignition. The traces are labelled on the left... Ch 1 (Yellow) is the crank sensor or "Pulser" coil. Ch 2 (Pink) is the fuel injector signal. Ch 3 (Blue) is the ignition coil signal. Ch 4 (Green) is the spark plug inductive pickup. The Pulser coil detects a row of holes in the flywheel. There appears to be a slot followed by 5 holes followed by another slot, then 2 more holes. These bursts occur every revolution of the crankshaft. In this shot, the engine is idling at 1720rpm. The fuel injector fires on the negative going pulse and stays open for the duration of the negative pulse (there is +12v on one side of the injector and the ECU pulls the other side to ground). The pulse width determines the amount of fuel injected. This pulse occurs every 2nd revolution of the crank at the start of the intake stroke. The ignition coil also has +12v on one side and the ECU pulls the other side to ground to create the magnetic field in the coil. The spark occurs when that ground is removed by the ECU and the field collapses. So the duration of the negative pulse is effectively the dwell angle (in old lingo). The spark trace is hard to see because it lines up with the trailing edge of the coil input. In any case, the spark occurs every second revolution in between the fuel injection pulses - no wasted spark. 1 Quote Link to comment Share on other sites More sharing options...
lemur Posted February 27 Report Share Posted February 27 (edited) The spark occurs every second revolution in between the fuel injection pulses - no wasted spark because it is timed off the crankshaft and not off the camshaft 😐. 👍 nice scope traces, are you sure the C1 yellow trace is the timing trigger and does not represent the alternator output? Edited February 27 by lemur Quote Link to comment Share on other sites More sharing options...
lemur Posted February 27 Report Share Posted February 27 18 field coils, 18 blips on the C1 oscilloscope trace. Quote Link to comment Share on other sites More sharing options...
aussiechris Posted February 27 Author Report Share Posted February 27 (edited) Not really. Those stator windings feed three phase AC to the rectifier/regulator to provide 12v DC to power everything. Those are connected via the three yellow wires on the 3 pin plug. There are multiple magnets in the flywheel passing those coils. Ch1 on the scope is connected to the Pulser or pick-up coil shown top right of your photo (with the two mounting holes). It sits external to the flywheel and detects holes and slots machined into the outside of the flywheel. That is connected to the white and green wires in the 2 pin connector. Most bikes have only one slot in the flywheel for timing but the 4RT has a row of nine then a gap. Edit: The Pulser wires are actually white/yellow and green/yellow. Edited Thursday at 09:29 PM by aussiechris Quote Link to comment Share on other sites More sharing options...
konrad Posted Thursday at 07:29 PM Report Share Posted Thursday at 07:29 PM 14 hours ago, aussiechris said: Ch 4 (Green) is the spark plug inductive pickup. What are you using to monitor that signal? I have a Hantek HT-25 "capacitive" probe, but never been too impressed with it. Supposedly 10,000:1, but I have doubts about the accuracy of that number. Quote Link to comment Share on other sites More sharing options...
aussiechris Posted Thursday at 09:54 PM Author Report Share Posted Thursday at 09:54 PM 2 hours ago, konrad said: What are you using to monitor that signal? I have a Hantek HT-25 "capacitive" probe, but never been too impressed with it. Supposedly 10,000:1, but I have doubts about the accuracy of that number. Hi Konrad. A proper high voltage probe would have been nice but I just used the clip-on inductive pick up from an old tach/dwell meter - remember those? Also used on timing lights. The red thing below... I just attached a BNC connector to make an easy connection to the scope. I thought it might be better than winding wire around the plug lead. The duration of the spark is extremely short. Unfortunately, at the relatively slow timebase needed to show the other signals, the spark impulse is just one pixel wide. It's hard to see but I just wanted to verify the spark occurs when the ground is removed from the coil - same as a traditional "Kettering" points ignition (and unlike CDI used on other bikes). Quote Link to comment Share on other sites More sharing options...
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