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Thread: General Info: How Injectors Work

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    Lifetime Member SSpdDmon's Avatar
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    Default General Info: How Injectors Work

    Due to some recent conversations about injector sizes, calibrations, etc., I did a quick Google search and found some pretty interesting (free) info that, IMO, is worth sharing for those who want to learn more about what's happening under the hood. They seem to do a fairly decent job explaining the basics.

    FYI - I'm including their whole zip file only because the text/PDF document I speak of references their Excel file quite a bit and I didn't know if anyone wanted to play around with it. As for the company, they do offer injector services for a fee. But, I can't speak to their work.
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    Last edited by SSpdDmon; August 19th, 2009 at 05:41 AM.

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    Paul Yaw is very knowledgable on injector behavior and is one of the very few people in the industry who actually recognize how to properly test the nonlinear flow region of the injector. You'll see a similar discussion in an article I wrote (hey this one is free too!) a while ago before reading Paul's work. The important point is that calibrators (or "tuners", if you will...) should recognize the facts that 1) injectors are not linear, and 2) not all injectors are non-linear by the same amounts.

    <LINK TO MY ARTICLE HERE>
    ~Greg
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    Lifetime Member Aloicious's Avatar
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    Quote Originally Posted by SSpdDmon View Post
    Due to some recent conversations about injector sizes, calibrations, etc., I did a quick Google search and found some pretty interesting (free) info that, IMO, is worth sharing for those who want to learn more about what's happening under the hood. They seem to do a fairly decent job explaining the basics.

    FYI - I'm including their whole zip file only because the text/PDF document I speak of references their Excel file quite a bit and I didn't know if anyone wanted to play around with it. As for the company, they do offer injector services for a fee. But, I can't speak to their work.
    Paul is a good guy, I've had a chance to talk to him quite extensively when I did my MPFI swap, I got my 24# injectors from him and had him do his dynamic testing on them. he provides alot of good info for them, its general scientific data for them, not specific to EFILive, but from his data I was able to extrapolate the oft unknown tables like variable voltage offsets {B3701}, small pulse adjust {B4005}, Small pulse threshold {B4006}, etc. basically most of the injector data tables that alot of us either use stock tables, or guess on since the data isn't widely available from the manufacturer. and its great because not only does he test these variables but other good info as well above and beyond the standard flow testing that injector testing usually provides. if I wasn't so poor I'd have him test my new 39# injectors too, but alas my wallet is on the light side from my whole 24x/whipple/T56 project. I can speak of his work from experience though and he does a very quality job.

    I have however recently acquired a quality high resolution oscilloscope, and when I have the time I've been looking into building a rig to test various injector dynamics, mainly out of curiosity. injectors fascinate me, they're simple, yet elegantly complex.

    for anyone interested I am selling the 24# injectors with all the info I have for them. some info on them can be foundhere
    however if anyone is interested in them please PM me so we don't derail this thread.
    Last edited by Aloicious; August 19th, 2009 at 07:50 AM.
    1996 c1500 gen1e 5.7L - the "LS31", 24x CNP, LS2 coils, modified T56, 12200411PCM running COS3, zz4 cam, custom MPFI, etc. coming soon: Twin Turbos

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    Lifetime Member SSpdDmon's Avatar
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    Quote Originally Posted by eficalibrator View Post
    Paul Yaw is very knowledgable on injector behavior and is one of the very few people in the industry who actually recognize how to properly test the nonlinear flow region of the injector. You'll see a similar discussion in an article I wrote (hey this one is free too!) a while ago before reading Paul's work. The important point is that calibrators (or "tuners", if you will...) should recognize the facts that 1) injectors are not linear, and 2) not all injectors are non-linear by the same amounts.

    <LINK TO MY ARTICLE HERE>
    I remember reading this a while back, but didn't remember who wrote it or where to find it. Thanks for posting...some good theory/observations there too.

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    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Aloicious View Post
    ...

    I have however recently acquired a quality high resolution oscilloscope, and when I have the time I've been looking into building a rig to test various injector dynamics, mainly out of curiosity. injectors fascinate me, they're simple, yet elegantly complex.

    ...
    Cool......scopes teach you a lot, what scope did you get...?

    I got a Picoscope from Autonerdz, see my waveform (see image, see the open dip and the close hump)... I haven't had much time to explore this further, but I intend to...

    I'm trying to figure out how to measure the amount sprayed...



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    Lifetime Member SSpdDmon's Avatar
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    I guess the one thing I'd like to see more of after reading this stuff is, how MANVAC affects the injector's flow in the time between full open and full close. I see mention of dead time and compensating for that based on commanded pulse widths and battery voltage. But looking that the tables we have available, GM thought it was relevant enough to add in this one more variant - vacuum - and it doesn't seem to be a part of the discussions above (unless I missed it).

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    Lifetime Member 5.7ute's Avatar
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    Quote Originally Posted by SSpdDmon View Post
    I guess the one thing I'd like to see more of after reading this stuff is, how MANVAC affects the injector's flow in the time between full open and full close. I see mention of dead time and compensating for that based on commanded pulse widths and battery voltage. But looking that the tables we have available, GM thought it was relevant enough to add in this one more variant - vacuum - and it doesn't seem to be a part of the discussions above (unless I missed it).
    Which tables are you talking about Jeff?
    The Tremor at AIR

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    Lifetime Member SSpdDmon's Avatar
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    Quote Originally Posted by 5.7ute View Post
    Which tables are you talking about Jeff?
    The battery voltage offset table is 3D and allows for MANVAC. That's what I'm getting at...and when we switch to bigger, slower injectors...I'm wondering if the effects of MANVAC are more pronounced.

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    Lifetime Member 5.7ute's Avatar
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    No worries, just making sure we are on the same page.
    The Tremor at AIR

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    Lifetime Member Aloicious's Avatar
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    Quote Originally Posted by joecar View Post
    Cool......scopes teach you a lot, what scope did you get...?

    I got a Picoscope from Autonerdz, see my waveform (see image, see the open dip and the close hump)... I haven't had much time to explore this further, but I intend to...

    I'm trying to figure out how to measure the amount sprayed...
    yeah its a Picoscope. I scored it used but in great condition for a steal of a price. but its also not their newest model but should work just fine for pretty much everything I would use it for though, including injector dynamics. thats a great image, I'm looking at the same thing, but I wanna build a flow bench type rig that I can adjust the voltage and pressure on to get a full range of injector characteristics over varying circumstances. SSpdDmon brings up a good point about Manifold vacuum too. I bet I could rig up something to account for that as well. interesting stuff, too bad it'll be a while before I can work on it due to work, school, and research that I have going on....
    1996 c1500 gen1e 5.7L - the "LS31", 24x CNP, LS2 coils, modified T56, 12200411PCM running COS3, zz4 cam, custom MPFI, etc. coming soon: Twin Turbos

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