57MPH Hum

Discussion in 'Prime Main Forum (2017-Current)' started by mr88cet, Nov 16, 2021.

  1. mr88cet

    mr88cet Senior Member

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    Wondering if anybody else has seen this too — well, heard it, actually:

    Over the past couple months or so, on my 2017 ‘Prime Advanced, with 66,741 miles, as I accelerate through 57MPH, at around 54MPH, I start hearing a … hum? As my speed increases, it peaks at around 57MPH, and then trails off, until at 60MPH or so, it’s pretty quiet again.

    Observed qualities:
    — Even at its 57MPH peak, it’s not overbearingly loud, but only slightly annoying.
    — It’s much quieter in hybrid mode than in EV mode, so it’s presumably some sort of resonance in the electric drive train.
    — It’s probably pitched at roughly the Eb above middle-C on the piano.
    — Its probably fairly sinusoidal-ish.

    Anybody heard anything like that?
     
  2. bisco

    bisco cookie crumbler

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    definitely not tires?
     
  3. Trollbait

    Trollbait It's a D&D thing

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    Tires would be my first guess; they can change noise with wear.

    Being louder in EV could just mean the engine noise covers some of the sound up.
     
  4. bisco

    bisco cookie crumbler

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    sometimes rotation can prove it
     
  5. mr88cet

    mr88cet Senior Member

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    Reasonable question, but no, definitely not tires:

    When I ease off the accelerator so as to hold at 57MPH, rather than accelerate through 57MPH, the volume of the sound goes down.

    Also, as I mentioned, it’s quieter at the same speeds in hybrid mode than in EV mode.

    It seems to be related to how much power the MGs are producing in the speed range.
     
  6. mr88cet

    mr88cet Senior Member

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    Oh, I also haven’t been able to isolate the direction the sound is coming from, so far at least.