What is the voltage of your "clamp" diode ?

 

I used IRF540n Mosfet.
https://media.digikey.com/pdf/Data%2...Fs/IRF540N.pdf

For the current test, the clamp diode was not in play. Mosfet was on solid. The graph may look like it's pulsed, but that's just how the graph came out.

 

The use of a Zener Diode "clamp" , a 1N5366B, will stop the inductive kickback created by a fuel injector and close the injector faster.

 

You know of course that the chart above does not include closing time.

But funny you should mention that, my buddy Steve believes that is true also. I don't, but we're going to test it.

Why zener, why not Schottky?

 

If anybody wants to build one of these, PM me and I'll send you my test version code (no liabilities, only a test version) and draw up a schematic.

 

I received 2 of my 4 load cells and started checking out their accuracy.

Load cell needs some way of supporting a graduated cylinder or plastic bottle, so I freeCADed and 3D printed some. They can hold a graduated cylinder or a regular 500ml plastic water bottle or a 1 liter bottle. I'm planning on using the 1 liter bottle to avoid having to empty it so often.




I then started testing. You need to calibrate these load cells the first time you use them. You get a base reading with the bottle empty and then get a second reading with the bottle filled with a known quantity of fluid. I used 100ml since the graduated cylinders are 100ml.

I was amazed how accurate the reading were. Accurate to about .05ml. That's over 10 times better than I can do by eye with the graduated cylinder. Load cells use an amplifier and analog to digital converter chip (hx711) which reads 24 bit accuracy.

The load cells I chose can measure up to 1 kilo or 1000 grams. A one liter bottle of water weighs 1 kilo. A one liter bottle of gas, diesel or mineral spirits weighs less than 1 kilo so I can use the 1 liter bottle and it's within the range of the load cell.

To get a higher accuracy with the load cells, you can read them multiple times. I did 60 readings and averaging, still quicker than me eyeballing the graduated cylinder.

So once I get the final set of load cells, I'm going to change the software. For each injector, I'm going to run a series of tests, reading the volume in the bottle before and after each test. So for a high impedance 1000cc injector, I might do a 1.5ms run, a 1.7ms, a 1.9ms, a 7ms, a 90% and a 100% run, and a injector startup current run all without having to empty the bottle. Just walk away and let it do it's thing. The results get sent to the serial port and then get copied to excel where it can be charted and saved.

For low impedance ones, I'd start lower. I'm open to suggestions about what tests to run, What is the industry standard for characterizing injectors?

 

Got all 4 load cells. Added a bunch of new screens to the touchscreen. I can run bulk tests now, The load cells are calibrated to spit out the difference in milliliters before and after each step single or bulk runs.

The 1 Liter bottles work much better than the graduated cylinders. I can run many tests without having to empty the bottle each time. And since the 1 liter bottle is wider than the graduated cylinder, there is no splashing and I can see the spray pattern of the injectors much better.

Results of bulk test are in CSV format so I can import them or direct stream them to Excel.

 

im following along, good stuff.
i put together a basic arduino controller to do this for a friend but nothing came of it. i finished the code and 3d printed enclosure and all that, just never handed it off and we both kinda lost interest i guess.

 

If I had to do it over, I would not use a fuel rail mounted regulator. This makes it much harder to empty the fuel rail before changing injectors.

 

Test of 3 different injectors varying pulsewidth from .7 to 3 milliseconds.
Injector 1 is siemans dekka 80 lb
2 is turbo dodge 2.5L stock low impedence
3 and 4 are 1000cc injectors.

y axis is milliliters

 

this project has lab view and one card chassis all over it.....

I love this though i had a similar idea a few months ago when I ran into an issue with sticky injectors and the money it woud cost to get them tested vs buying a new set...... I bought a new set.

the swap to the load cells is smart as long as weight of container and weight of fluid other then gasoline is accounted for assuming they differ.

 

I also bought a new set. I paid a little extra because they said they were matched. The matching wasn't that great, especially at the lower end. Let's face it, do we really trust stuff in ads? With all the work I put into the car, I'd rather not risk it while under boost. Also, I can compensate for each individual cylinder, so matching isn't as critical if you know what the injectors do.

It's all accounted for. To calibrate, I bought a 500ml graduated cylinder. Then filled that 500ml of the test fluid into one of the empty bottles. My calibration routines first weighs the empty bottle and then the 500ml identical bottle. The fluid I used is mineral spirits, which has a viscosity close to gasoline.

The load cells was the best thing I changed. The small size of the 100 ml graduated cylinders caused a lot of spray and mist as well as having to empty them and read them by eye. And you could see the spray pattern nearly as well. Now I push one button and it goes through an entire series of tests while I walk away.

 

I made 2 more changes and I think I'm pretty much done changing stuff for now.

I changed the fuel rail to one without a built in regulator and mounted a standalone regulator instead.
Now that the regulator is not attached to the fuel rail, I added a small air pump with a check valve so that I can empty all the fluid in the rail and hoses when I want to swap injectors. Changing injectors is a breeze now, no more fluid spills. I'll get a photo if the updated version.

 

Here are some more charts.

This one is in 1 ms increments to 93% duty cycle for the deka80 turbo dodge low impedance, and the two 1000cc injectors. Notice how the two 1000cc injectors are not matched.


This one is for the same 4 injectors and shows the current every 25 micro seconds. The low impedance one was scaled down by a factor of just so you can see the timing of it relative to the high impedance ones.

 

I AM impressed! You have mad capabilities with electronics and all associated with it.
First with your PWM Arduino fan controller, and now this.
I'm a fan.

 

Very impressive. If you ever make a version to sell let me know. I have been looking at the AUtool ones to buy, but would rather support a real person.
I have to clean and flow a couple times a year.

 

Appreciate that you want to support a real person. Sorry to disappoint, but I have no intentions of going into business. I offer the software to anyone interested in building one for free and might possibly make up a circuit board if there is enough interest, but don't plan to make money off this.

I've only seen the AUtool one in ads. Don't know how it works, I don't believe it has the automation and reporting that this one has. I've also heard that the fuel pump is marginal.

On my current version, literally, push a button, walk away and get a detailed view of 4 injectors operation and characteristics, at every pulsewidth as well as opening current characteristics. Only trouble is that you gotta build it.

 

I added an air pump the empty all the fluid out of the lines and injectors so there is no fluid mess when swapping injectors. The injectors are bled dry before removal.

I also added a bunch of bulk tests so you run it, walk away, and all the characteristics are printed out.

BTW, in the video below, the injectors are not all firing at the same time. They are firing 180 degrees apart, just like in a real engine.

 

Hi If you still open to share build details I would love to build one of these

 

I'm going to draw up a diagram and a rough parts list.


The connector on the left goes to all the load cells. 4 wires go to the touchscreen(+5, GND, rx, tx). I wire for each of the injectors and one for the fuel pump. and of course power supply and grounds.







Basically, 5 IRF540 mosfets, a .1ohm resistor for measuring injector current, a few more resistors, an arduino mega, a 2.3" nextion intelligent touchscreen display, 4 1kg load cells and A/d boards. I'll provide more details and 3d print files for the bottle holders and load cell mounts.

I'll load the software somewhere so it can be downloaded. Too long for inline code on here.