New car, whirring sound when accelerating from low speed

Discussion in 'Clarity' started by DC2, Apr 14, 2018.

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  1. DC2

    DC2 Member


    I just recently purchased a 2018 plug-in Clarity yesterday. On the drive home (in I presume normal EV mode with no buttons pressed), I noticed that there's a whirring engine/generator when I step on the accelerator between 25% to 50% speed going from 25 to 40 mph (shown in orange in the picture). Is this normal behavior for the clarity?

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  3. DC2

    DC2 Member

    Last edited: Apr 14, 2018
  4. DC2

    DC2 Member

  5. KentuckyKen

    KentuckyKen Well-Known Member

    That is indeed the trigger. The ICE is trying to put some charge in your depleted (2 bars on guage is full useful capacity depleted) battery so that it can switch between all of its power modes and give you the best mpg. I have found that I can avoid the high reving/angry bees by manually selecting HV mode (not HV charge) before full usable battery depletion at 2 bars remaining. Then I only get a barely noticeable “fast idle” kind of sound unless I hit a steep hill or call for maximum acceleration.
    Sounds like your car is acting normally. Try charging the battery and I bet your “problem” will go away. Please try and post what happens. We need all the data points we can get to figure the Clarity out.

    Other posts have mentioned that the dealers don’t understand this and will give test drives with the battery depleted and the high reving/angry bees will make potential buyers think it’s a noisy car when almost always it’s the quietest car out there.
  6. barnesgj

    barnesgj Active Member

    I concur with KentuckyKen. Only occurs when the battery is depleted. I had an appointment to get it looked at, too, but canceled it after the input from this forum. Am not ready to have the mechanics poking around under my hood.
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  8. DC2

    DC2 Member

    I was able to take a video on my way to charging. Here it is on Google Drive:
    The sound becomes very apparent around 16 seconds in. ALthough I was driving under 30 mph, it sounds like the engine was running super hard. This was running with HV mode on I believe, but the same sound occurs without HV mode.

    After charging ~1h20min to ~60/70%, the car ran super quiet and was normal.
  9. kkiran

    kkiran Member

    I see random engine revs but it only happens when I like some fun on the road!

    It is so eerily quiet for a Honda, never experienced this before (Tesla is an exception). Can’t wait for enhancements in the next generations of the Clarity.

    Sent from my iPhone using Inside EVs
  10. Once your battery is down like that the car operates the same as in HV mode, as you discovered.
    For the Chevy Volt this is described as Charge Sustainment (CS) mode.
  11. DC2

    DC2 Member

    Is it supposed to be that loud in HV mode? I was around 33% battery this morning and when I turned on HV, a lot of reving occured. Is there a way to switch to only gas powered?
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  13. I think you'll find that the car initially "falls behind" in battery charge while the engine is initially warming up then races to catch up if you switch over at highway speed. Try pushing the button a minute or two before you get on the highway so that the engine can warm up a little before it has to get to work.
    Let us know if that helps.
    Johnhaydev and KentuckyKen like this.
  14. DC2

    DC2 Member

    Hmmm, I've been switching to HV on local roads so I don't think it's highway speed's that's causing the revving. After service today, the technicians mentioned that it's normal.

    I'm going to try this tomorrow and place the Clarity into HV Charge Mode (29s in the youtube video) and turn EV off just for instances where my power is low but I want to drive without the revving sound.

  15. DC2

    DC2 Member

    Drove local, pushed car into HV charge mode at about 35% power. There was a different hum from the engine and a slightly different by similar revving/rumbling from the engine. I guess these engine sounds are just from the EV charging. Is there a way to go into a no charge, gas-only mode?
  16. That's what short press HV mode is (in a hybrid sort of way).
  17. DC2

    DC2 Member

    It seems that short press HV is still charging when power is low. Given that I don't have a charger at home, when I'm low on power (~33%) revving occurs:
    1. When I'm in EV mode
    2. When I'm in HV mode
    3. When I'm in HV Charge Mode
    4. When I'm in sport mode
  18. Now I understand. Use HV charge mode to get the battery up a bit (say, 50% or so) then HV mode should be less noisy when you use it.
    Purely gas mode isn't practical because it's a small Atkinson cycle engine and would be really gutless without the battery to help at times.
    Johnhaydev and loomis2 like this.
  19. Lash

    Lash New Member

    Hello, I too am having a high uncontrolled revving and rpm issue and loss of acceleration with my clarity. It has 1800 miles on it and has happened four times with two trips to the dealer. The dealer and service has been very helpful but they are learning about this car as I am so are clueless at this point. The first three times the high, uncontrolled rpm and loss of acceleration occurred at low speeds, 25-35 and with battery depleted and car was in auto hv mode to charge battery. The mode it faults to when you are driving in ev mode and you deplete your battery pack. The dealer could not find anything wrong nor could they find any codes and said this is normal. I called Honda to open a case file because this did not seem right nor was it what I consider a normal mode of car as I know it. I did discover from a very helpful sales rep at dealer that if you hold down the hv button for five seconds or longer, it will put the auto into hv charge mode and this will charge battery pack up to 53% or so. I decided to do this and try not to deplete battery thinking this high uncontrolled rpm rev from gas motor (ICE) was a quirky thing it does when charging depleted battery. Degenerately worked for a month or so until last week I was cruising at highway speed, 68, in hv charge mode with 6 bars on battery gage the ICE suddenly, with no change in my driving, just traveling with traffic, revved so loud and a high rpm I heard it over the radio. I also lost acceleration and cars began to beep behind me. I pulled over to right lane and put my foot on the gas again and it revved uncontrollably to the point I thought it would damage engine. I then pushed the sport mode button, this seemed to help gain some acceleration back when it happened at slower speeds but did nothing at this point so I immediately pushed the hv button which switched the vehicle into ev mode, cutting the ICE, as it should, and getting me to the hotel in ev mode. Immediately called the dealer and Honda to report the potentially dangerous glitch and it is sitting at the dealers as I write this. Service first thought it might be a transmission issue but now hearing of other folks having this problem, they think its a software issue. Love the car but do not feel comfortable traveling on the highway with my family in the car especially with this looming glitch.
  20. bfd

    bfd Active Member

    It's an undocumented feature. Too bad it's not documented, but I can see why Honda would want to bury it. Doesn't happen often, happens under pretty predictable circumstances, and doesn't last long.

    However, enough of us have experienced the phenomena that it probably should be documented somewhere else besides here.
  21. loomis2

    loomis2 Well-Known Member

    His story sounds like all the others except for the loss of acceleration. It has only happened once to me a few months ago but I don't remember the car driving any differently, just that the engine was revving fast.
  22. KentuckyKen

    KentuckyKen Well-Known Member

    And then some of us are reporting no high revs. Mine is just a barely noticeable medium rev (no hard accel, no steep hill, no extreme temps). The loss of accel points to a problem that needs warranty repair.
    Posts on this forum seem to indicate that there is a somewhat large variation in behavior among our Claritys. I have no idea why and no idea why it occurs with no error codes generated.
  23. Lash

    Lash New Member

    Hey folks, yes, I find it strange there are no codes thrown but makes me think the computer thinks it’s operating normally when this happens. I have to explain, normally the car runs great and it too has that medium rev but when this glitch happens, It’s not total loss of acceleration but very different gas pedal response. Normally in all conditions the car accelerates as you press the gas pedal and reacts accordingly, during the glitch, the car does not accelerate or is not as responsive to the gas pedal being depressed and in addition to the slow acceleration response the more you step on gas the higher the rpm of the ICE to the point it will kill the motor or sound that way. The last time it happened on the highway it was as if you were cruising in your regular car, cruising along and just threw it into neutral, the ICE suddenly revs to a high rpm to the point you need to take your foot off the gas or it will blow. Crazy stuff. I am trying to be patient and take as many detailed notes to help Honda figure out the issue, it’s an important and dangerous issue but I have two young kids and need a safe functioning vehicle. I will hold out as long as I can and hope I or Honda can shed some light on the matter, cheers and thanks for the support. I will keep you posted!!!
    Louis Nisenbaum likes this.

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