What is this cover/compartment?

Discussion in 'Gen 3 Prius Main Forum' started by 10PriusIV, Sep 17, 2020.

  1. 10PriusIV

    10PriusIV Junior Member

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    Probably a very easy question, but before I take it off to see and attempt to clean it, I'd like to know. I'm tying to track down the 35 MPG cause. We have 143k on this 2010.... and is using a small bit of oil now.
    TIA!!

    Prius cover.jpg
     
    #1 10PriusIV, Sep 17, 2020
    Last edited by a moderator: Sep 17, 2020
  2. Raytheeagle

    Raytheeagle Senior Member

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    It's part of the air intake system;).

    Resonator I believe it is called(y).
     
  3. ChapmanF

    ChapmanF Senior Member

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    That there is more or less a Helmholtz resonator. It is very unlikely to be a source of intake obstruction, because the airflow does not go through it. If you look closely, it attaches to the side of the air passage; the air flows past it, like playing a flute. That also means probably nothing is likely to get randomly sucked into it.

    It allows air to flow through the intake ducting smoothly, even though the engine sucks in short pulses. At key engine rpms that the resonators are tuned to (there's another smaller one too, you'll see it if you look), the inside of the resonator will be at a pressure low and suck some air when the engine isn't, and when the engine intake valves do open, the resonator will be at a pressure peak and help to force air in.
     
  4. Maarten28

    Maarten28 Active Member

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    Wow, dusty environment much? :eek:
     
  5. Mendel Leisk

    Mendel Leisk Senior Member

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  6. ChapmanF

    ChapmanF Senior Member

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    It's a resonator, honest. At the right frequencies it will contain a standing pressure wave that sucks air when the engine isn't, and helps blow it into the engine when the engine is.
     
  7. jerrymildred

    jerrymildred Senior Member

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    What @ChapmanF said. I think of it as a shock absorber that dampens the pulses of incoming air. The engine doesn't draw a steady flow of air, so the air would have to stop and start. The intake pressures at the intake valves would be constantly fluctuating. The resonator helps give the engine a more consistent intake air pressure.
     
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  8. Mendel Leisk

    Mendel Leisk Senior Member

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    @mjoo might be interested; IIRC he's removed everything before the air box?
     
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  9. mjoo

    mjoo Senior Member

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    IMHO, all it does is add time to the book hours rate for various repairs. I notice no elevated noise level taking it off and I have pretty good hearing. Maybe it's at a frequency I can't hear...

    It may make a difference later when my engine has more wear. Maybe.
     
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  10. ChapmanF

    ChapmanF Senior Member

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    It's better to think of it as a spring with no shock absorber.

    If your suspension were built with just springs and no shock absorbers, the ride could get very bouncy. The springs would give back all the energy they took up. There would be a resonant frequency and if you happened to drive the right speed over a bunch of moguls at that resonance, the car would bounce like crazy. The shock absorber is there to make that energy go away, by using it to heat up oil by squishing it through little holes.

    The purpose of a shock absorber is to kill resonance. The function of a resonator is to have resonance. It's a big empty chamber, nothing in there trying to make the energy go away.

    When the engine intake valves close, air is flowing. It keeps flowing (inertia), storing that energy in the resonator. When the next valves open, the air-pressure 'spring' gives the energy back, shoving the air into the engine.

    At whatever resonant frequency it is tuned to, its pressure is a repeating wave: its pressure lows are sucking air in from the snorkel when the engine isn't, and its pressure highs are feeding the engine.
     
  11. jerrymildred

    jerrymildred Senior Member

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    That's a much better way to say it. Thanks. And good explanation.
     
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  12. 10PriusIV

    10PriusIV Junior Member

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    Yes.... 10 years+ of California desert! I am a Dutch-American and lived in Apeldoorn en Fochteloo, so I know where you're coming from lol...
     
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