how to test fuel injector?

[Valkyrie]

going to get some second hand fuel injector from TM? How do I test them if they works? can I just feed 12V DC to the terminal?

[Guest boostcut]

no because the solenoid could still click and it may have a poor spray pattern/ flow.. tbh id go thru a wrecker as they give a warrenty

[suubyduuby]

 Valkyrie said:

going to get some second hand fuel injector from TM? How do I test them if they works? can I just feed 12V DC to the terminal?

From memory, injector flow is determined by a contunuous stream of pulses from the ECU. The duty cycle ('on time') is varied to increase the flow of the injection spray.

To test spray, you'd need to pulse the thing in a similiar way to how the ECU does it. Feeding 12V into it will put it fully on, but I guess you won't be able to test varying the injection as a normal ECU does.

I could probably sort you out with a controller circuit to test it if you'd be interested?

[Joker]

is that how they "flow test" injectors? (try google I know some Venom injectors were bad news)

[Valkyrie]

 suubyduuby']

[quote name='Valkyrie said:

going to get some second hand fuel injector from TM? How do I test them if they works? can I just feed 12V DC to the terminal?

/quote]

From memory, injector flow is determined by a contunuous stream of pulses from the ECU. The duty cycle ('on time') is varied to increase the flow of the injection spray.

To test spray, you'd need to pulse the thing in a similiar way to how the ECU does it. Feeding 12V into it will put it fully on, but I guess you won't be able to test varying the injection as a normal ECU does.

I could probably sort you out with a controller circuit to test it if you'd be interested?

Is it truth that as long as the injector pump fuel, they works fine? So if I apply a 12V and it runs they it is fine? Varying the injection strength would be the job for the ECU which is not I worry about.

[Durty-Sanchez]

Get a bucket or container (ie kitchen ones) that have litres/milli litres marked on them, you'll need this as an indication that the injector is flowing near it's rated value. You'll then need to rig the injector up to a fuel pump/regulator that matches that in your cars setup. Apply 12v (100% on) to the solenoid for a given period of time and compare how much gas ends up in the container to how much you would expect. i.e. 440cc injectors are supposed to flow 440cc (440mL) a minute. If you let it run for 2-3 minutes you'd then expect 1.32 litres of gas in your container (the longer you leave it running the more you can average out the flow over the time period to get a more accurate idea of the injectors actual flow rate).

Some warn about placing an injector on at 100% (using DC 12v) though incase the injector sticks/shorts out, so it may be an idea to create a pulse circuit to drive the injectors at 90-95%, as your ECU would be unwise to push much past this anyway.

If you can't be bothered rigging up the above test-setup with fuelpump, petrol supply, fuel line. regulator, pulse circuit, etc. then i'm sure there are folks around who flow-test injectors all the time who could do this no worries.

[Pappu1]

think nz efi do testing - 80 of so for a full test and report from memory

why u wana test injectors lol.. ur s202 already have the 575 sti pink ones..

[Koom]

Just as a note, the 440cc Yellows will flow ~520cc's at 100% Duty cycle and the 380cc Grey's flow ~460cc at 100%.

Injectors are generally rated at 80% duty cycle (I'm guessing there's a standard to follow) but as far as testing at home goes its just simple to hook up at 100% duty cycle. There's calculators available on the intarwebs that will then let you figure out how much they flow at various duty cycles (i.e. at 80% to check against their rating).

If you read up the American stuff (often from RC Engineering) their stuff is rated at 100% as the Yanks will refer to the early Yellow STI injectors as 550's and the Grey's as 440's.

[Valkyrie]

 pappu said:

think nz efi do testing - 80 of so for a full test and report from memory

why u wana test injectors lol.. ur s202 already have the 575 sti pink ones..

not for the S202, asking for my mate who want to do upgrade. ;D

[suubyduuby]

 Valkyrie said:

Is it truth that as long as the injector pump fuel, they works fine? So if I apply a 12V and it runs they it is fine? Varying the injection strength would be the job for the ECU which is not I worry about.

Yeah as Durty-Sanchez wrote though, dunno if its a good idea to give the poor injector a full blow of 12V. Because the ECU is always pulsing them, they are very rarely if ever fully-on. However, I'm sure they would survive for a quick test.

In order to 'flow-test' them, I believe you would want to vary the 'on time' of the injector and check whether it is delivering its rated flow at that duty-cycle. THat way you can accurately test their performance over a range of duty cycles (as would normally happen when controlled by the ECU).

Duty-cycle is measured between 0-100% - where 0% is OFF and 100% is fully on (ie. 12VDC). In between, the 'width' of the injector pulse is varied. If the injector is on a 75% duty cycle, then your injector basically sees an average voltage of 75% of 12V = 9V. Cos the voltage is lower, the injector doesn't open fully and so-on. Same way electric water pumps and solenoids are controlled.

Some diagrams:

What the injector pulse timings look like

A control circuit which you could use, if you're game

[Koom]

One issue I'd have with getting reasonably reliable results from a homebuilt setup that incorporated a PWM device, is measuring what the exact percentage is that you are rating the injectors at. i.e. needing an oscilloscope to show you if you have 80% - 81% - 82% and so on. Whats the uncertainty in the width of the pulses etc? As this will effect the accuracy of your results and the effect could be quite large.

With the setup I had, we calculated an uncertainty of only +/- 0.5% for the smaller injectors and +/- 1.0% for some 740cc injectors that I also tested.

[suubyduuby]

 Koom said:

One issue I'd have with getting reasonably reliable results from a homebuilt setup that incorporated a PWM device, is measuring what the exact percentage is that you are rating the injectors at. i.e. needing an oscilloscope to show you if you have 80% - 81% - 82% and so on. Whats the uncertainty in the width of the pulses etc? As this will effect the accuracy of your results and the effect could be quite large.

With the setup I had, we calculated an uncertainty of only +/- 0.5% for the smaller injectors and +/- 1.0% for some 740cc injectors that I also tested.

You're right - with this setup you can vary the pulse width BUT the degree of accuracy in relation to the potentiometer is an uncertainty. This is a very simple circuit I found to easily generate PWM without a microcontroller...

What I would do if I was making a proper tester is use a microprocessor to generate the PWM. Have it so you can set it to exactly 50% 75% etc and the micro WILL produce exactly that on the pulse output pin. A little tool in a black box with a screen and couple of buttons would do the trick nicely.

If there was a demand for something like this, would do a run of 10 boards or so. You could also adapt it to pulse solenoids and other stuff for a timed intercooler water spray unit ;D Nice and easy-to-use general controller unit. Who knows?

[Valkyrie]

 suubyduuby']

[quote name='Valkyrie said:

Is it truth that as long as the injector pump fuel, they works fine? So if I apply a 12V and it runs they it is fine? Varying the injection strength would be the job for the ECU which is not I worry about.

/quote]

Yeah as Durty-Sanchez wrote though, dunno if its a good idea to give the poor injector a full blow of 12V. Because the ECU is always pulsing them, they are very rarely if ever fully-on. However, I'm sure they would survive for a quick test.

In order to 'flow-test' them, I believe you would want to vary the 'on time' of the injector and check whether it is delivering its rated flow at that duty-cycle. THat way you can accurately test their performance over a range of duty cycles (as would normally happen when controlled by the ECU).

Duty-cycle is measured between 0-100% - where 0% is OFF and 100% is fully on (ie. 12VDC). In between, the 'width' of the injector pulse is varied. If the injector is on a 75% duty cycle, then your injector basically sees an average voltage of 75% of 12V = 9V. Cos the voltage is lower, the injector doesn't open fully and so-on. Same way electric water pumps and solenoids are controlled.

Some diagrams:

What the injector pulse timings look like

A control circuit which you could use, if you're game

???too technical ??? I think I will just believe they are working fine hahaha

Can I clean them with degreaser to clean them by the way?

[Guest boostcut]

no you ultra sonically clean them.

[Valkyrie]

 boostcut said:

no you ultra sonically clean them.

woooo then I will need to use my toothbursh.

[Guest boostcut]

haha well your teeth would be clean in the morning..... na if you send them to petroject they will test and clean them for you and provide before and after flow rates too... for around 80 bux