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Injector Testing Fred/FreeEMS Style - COMMENTS 
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Fred since you locked your topic about this, ill do it this way.
Have been testing injectors myself at the 0.8 to 2.0 msec. and used a kitchen scale to measure the injector output.
weight x constance = volume


Fri Feb 14, 2014 6:25 pm
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The thing is, finding accurate and reliable weight or volume measuring devices is not easy, however finding accurate linear measuring devices is trivial as is the math. Hence I feel I'll get better results this way. I can try some alternatives and compare accuracy too, though, I guess.

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Fri Feb 14, 2014 9:54 pm
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FWIW, I bought some of these cylinders to test injectors with. $13 shipped and the quality seems more than fine for what we are trying to accomplish. I wanted 6 of them, but decided I could get by with just two for now. Eventually, I'd like to build a nice dedicated test/flow bench & these should be perfect for that.

http://www.ebay.com/itm/Graduated-Cylin ... 1c31b896c0

Len


Fri Feb 28, 2014 4:24 am
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Thanks for the link :-) The beer making tin was completely free, though, and fits with my current budget (zero) a lot better. A graduated cylinder of some type would make it easier to test the dead time and pulsed flow, though, that's for sure. I think I'd want a 1000ml cylinder because to do a sufficiently long flow test will fill that much with any reasonably big injector (and who cares about small stuff?). A smaller set in conjunction would allow the smaller pulsewidths to be more accurately determined, though. Unless the big one was just so much longer as to contain the liquid and provide the same precision.

In any case, I'm getting GREAT data and learning various things as I go. For example, to test a spray pattern it's nice to spray the injector into an open clear vessel of a larger diameter. However to test flow it's better to fit a hose over the end of it and let it spray contained fuel and reduce vapourisation (both for accuracy and safety).

Fred.

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Fri Feb 28, 2014 6:56 am
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If the can works, it's tough to beat free. :D

You're timing on this post is great, BTW. I'm just now gearing up to do some similar testing & it would be interesting to have both setups test the exact same injector (under same set of conditions of course) to see what differences occur between the output stages of the different ECUS.

My assumption is that when using dropping resistors, most all fet driven output stages will behave extremely close to one another & thus deliver the same correspondingly similar amount of fuel. But it would be nice to have some data to prove/disprove that. I just don't have any feel for how output drive strength (of the fet, not the dropping resistor ) affects the opening time. Driving them P&H I think really opens it up though because now software difference come into play.

Len


Fri Feb 28, 2014 1:21 pm
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superlen wrote:
My assumption is that when using dropping resistors, most all fet driven output stages will behave extremely close to one another & thus deliver the same correspondingly similar amount of fuel.

Yes, and this applies to high-Z too. The percentage difference in voltage or current at the injector due to 5-100mOhm of FET is going to be very insignificant.

superlen wrote:
But it would be nice to have some data to prove/disprove that. I just don't have any feel for how output drive strength (of the fet, not the dropping resistor ) affects the opening time.

I don't think that's necessary, really. If you treat the injector separately then it's easy to see what effect a particular resistance change will have on it.

superlen wrote:
Driving them P&H I think really opens it up though because now software difference come into play.

Absolutely, yes. :-) Not just software, though, hardware details, too.

Fred.

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FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
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Mon Mar 03, 2014 2:16 am
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