Fuel injector replacement

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Olscratch, Sep 6, 2019.

  1. ASRDogman

    ASRDogman Senior Member

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    I couldn't see anything coming out. But I will take your word for it. :)
     
  2. spiralhelix

    spiralhelix Active Member

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    Yeah, it was harder to see in that vid. probably camera position. If you watch it on full screen on a big monitor it’s more visible. The first couple pulses are easier to see as well.


    -Spiral
     
  3. ASRDogman

    ASRDogman Senior Member

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    I went full screen on my 15 inch MBPro, and slowed the video down to .5.
    Then I could see it, barely. A darker background and it would have been easy to see.
    Looked clear to me though.
     
  4. ChapmanF

    ChapmanF Senior Member

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    The point isn't the current it draws though. These things are engineered, meaning somebody did calculations around how much V²/R heating takes place during each injection pulse, and made sure that much heat can be carried away (by conduction, convection, radiation from the injector, and by the fuel flowing through it) before the next pulse, with the peak temperature attained in that process being within what the device can stand. Keeping them compact and cheap is among the objectives, so they're not super-over-engineered for being operated in ways that weren't assumed in the calculations.

    Similar cautions apply to other small solenoid valves in similar applications, like the ones in the brake actuator.

    Rich's suggestion is a good way of dialing back the damage risk, because backing voltage from 12 to 9 (a 25% reduction) is a 44% reduction in heating (because of that ² in V²/R). If a task calls for getting the thing to open enough to pass some fluid through, and some voltage lower than 12 is enough to do the task, it helps with the safety margin.

    Maybe a literal 9 volts can be too low. Looking back, I remember I was using an "Imedion" rechargeable 9 volt. Most rechargeable "9 volt" batteries have an even lower output voltage than a plain-Jane 9 volt, because they are just built by swapping NiMH (at 1.2 volts each) for the six 1.5 V cells in the plain-Jane one, and end up with 7.2. Imedion shoehorns two more cells in, ending up at 9.6. (I don't know if anybody out there splits the difference and sells a seven-cell, 8.4 volt "9 volt".)
     
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  5. ASRDogman

    ASRDogman Senior Member

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    Usually it's 8.4v. A 1.5 v battery is 1.25v
    I don't remember exactly how it was explained but simply a "device" that calls for 9 volts
    needs a constant 8.? volts, can't remember if it's 1,2, or 3. And a rechargeable battery holds
    a constants voltage, then dies. A none rechargeable will slowly loose voltage.

    I don't know all the math and science to it, and it doesn't matter to me, as long as it works! :)
     
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  6. ChapmanF

    ChapmanF Senior Member

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    The 'it' has to be specified, because different battery chemistries produce different voltages. The super-familiar alkaline cell's nominal voltage is 1.5, which a spanking-fresh one can exceed a bit when under no load. A standard alkaline "9 volt" is a little stack of six of those, so its voltage is 1.5 ✕ 6, or 9 volts, to no one's great surprise.

    Both NiMH and, earlier, NiCd have slightly lower nominal cell voltages, both 1.2 volts. Early rechargeable versions of the "9 volt" still stacked only 6 cells, so the voltage was way lower than an alkaline 9 volt, down at 7.2. It would run some devices but not others, Back in the NiCd days, apparently "some manufacturers such as Varta" made seven-cell stacks, getting closer to the 9 volt target by adding up to 8.4.

    That seven-cell, 8.4 volt stack may be the most common flavor of NiMH "9 volt" these days, while also some, like Imedion, cram in an eighth 1.2 V cell so they end up at 9.6.
     
  7. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I measured a fresh alkaline 9 volt: 9.29 volts.
     
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  8. ASRDogman

    ASRDogman Senior Member

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    It's just a battery.
     
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