[diesel_john]

i have used timing lights that use the signal from a little split collar that bolts around the injection line. it has a piezo crystal in inside which senses the expansion of the steel line as pressure builds inside before/as the injector needle pops off. looking at the signal on a scope, it does a fair amount of ringing after pop off and during injection. separating the strain from all the acceleration in the area, would be part of the signal processing fun. the timing light only needed the highest peak in the time domain. but the line is definitely expanded while fuel is being delivered. i have used a knock sensor as an accelerometer, but they have their own resonance right the middle of the frequency spectrum to confuse the issue. gas grill igniter...
I need to measure the return fuel to see if it is inversely proportional to the fuel used, one of these days..