I think the main thing you need to measure is pulse width. I am not sure if the injector frequency changes at all but I know the % on to the % off ratio is where you can tell how long the injectors are open and how much fuel they are dumping into the engine. I am not sure if anyone makes a meter to measure it though.
If you can find one let us know cause I would like to have something to measure the injectors with
I think the main thing you need to measure is pulse width. I am not sure if the injector frequency changes at all but I know the % on to the % off ratio is where you can tell how long the injectors are open and how much fuel they are dumping into the engine.
As has been said, measuring the frequency would tell you how often the injector fires, but now how long it stayed open and therefor how much fuel it injected.
What you're looking for is something to measure duty cycle at a relatively quick pace. Many automotive multimeters have this function. Just check the package to make sure it will register values from 1-2% on up to 80-90%.
almost all engines base the injector opening time on rpm. you need pulsewidth AND frequency. frequency is rpm (usually not /2) usualyl based off the crank angle sensor (cam position sensor (located in the distributor in non-coilpack ignition) in older cars) pulsewidth is based on rpm, airflow/temp, and load (throttle position)
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1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
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A simple low-tech way to measure relative consumption would be to build a circuit that drives a meter or a lamp off of a capacitively charged circuit that gets it's input off of one of the injectors. Obviously faster or longer pulses will convert to more throw or lighting of the meter.
It would be relatively easy to design using a buffer driver and an LED bar graph IC or other digital display. It would be more of a challenge to get real world numbers out of it, but calibrated to read a 1 at lowest load and 10 at the highest, one could certainly make some reasonable assumptions about efficiency.