Frequency Counter as FE Meter?

[FritzR]

I'm thinking about trying something like this for a FE meter

http://cgi.ebay.com/9999Hz-LED-Digit...QQcmdZViewItem

It seems like it would be handy for counting injector pulses to see what gear would be best for driving to see if it's better at 1500 rpm in one gear or 2000 rpm in another etc

[CoyoteX]

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

[cfg83]

FritzR -

Sorry, can't say anything intelligent. This just looks plain cool! If not for an FE meter, why not for another type of gauge? What else could be called a "frequency sensor"? An A/F ratio meter?

CarloSW2

[Rick Rae]

Originally Posted by Coyote X

I am not sure if the injector frequency changes at all...

Erm... injector firing frequency would be directly related to RPM, wouldn't it? As in, RPM/2 on any given injector for a four-stroke?

Rick

[bobc455]

Originally Posted by Rick Rae

Erm... injector firing frequency would be directly related to RPM, wouldn't it? As in, RPM/2 on any given injector for a four-stroke?

Rick

I think some TBI systems don't correspond exactly to RPM. But even there, without measuring pulsewidth, there is no way to tell how much fuel is being used.

[FritzR]

Oh well just a thought. I thought the injectors put out a certain amount of fuel for each pulse

[Rick Rae]

Originally Posted by bobc455

I think some TBI systems don't correspond exactly to RPM.

Ah... I didn't even think about throttle body injection. Thanks.

But even there, without measuring pulsewidth, there is no way to tell how much fuel is being used.

Sure. I was just commenting on whether the injection rate changed or not.

Rick

[GasSavers_bobski]

Originally Posted by Coyote X

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.

Exactly.
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%.

[kamesama980]

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)

[Snax]

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.