Injector PWM settings measurements

[arsenix]

I rigged up a DIY current probe (an old timing light clip on probe + adding ~30 turns of wire to the pickup) and monitored the current in my injectors with my scope. My goal was to deduce the opening time of my injectors and figure out the required PWM current. I -think- I'm seeing the opening event on the scope, but I am unsure how to tell whether the PWM current is high enough. These are low impedance bosch injectors, 330cc/min.

Some scope "captures" (bear with the quality... my scope is not fancy enough to have USB). The timebase is 50uS/division in each shot.

Here is a series of different PWM time threshold settings: (all with 20% PWM current)
1 ms threshold
1.2ms threshold
1.3ms threshold
1.4ms threshold
1.6ms threshold

This led me to set the PWM time threshold to 1.4ms, since the 1.3 did not seem to open all the way.

I tried 20,15, and 10% PWM current threshold at 1.4ms time thresh:
20%
15%
10%

Anyone else look at injector current data like this? Does my data look similar? Is the idea with the PWM that it reach approximately the same current level as the injector was at when it opened?


James

[arsenix]

I realized that my pickup that I made is actually reading the differential of the current, not actual current. If I could read actual current I could calibrate it to set the PWM current of the injector to the correct setting. I attempted to use the integrate math function of my scope and calibrate it but it did not seem to work well. I guess I'll try adding an analog integrator with an RC circuit.

James