Does the gasoline engine start and stop while driving in Hybrid mode

Discussion in 'Prime Main Forum (2017-Current)' started by leaftoprius, Jul 2, 2018.

  1. leaftoprius

    leaftoprius Junior Member

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    While in Hybrid mode (either because I have used up all the battery for EV only driving or because I select Hybrid mode manually to preserve the EV only battery for later use), I notice the green "car" icon in the display (on the screen where you see the driving guidance for better fuel economy) occasionally turns on (fills in with green color, instead of just the outline of a car) when I lift my foot from the accelerator slightly or simply coasting on flat road. I thought that means the traction motor (not the gasoline engineer) is moving the car.

    So does that mean the gasoline engineer starts and stops as needed to save gas even while I am cruising on the highway?

    I know some newer cars (regular ICE) can shut the engine when waiting at red light and start the engine when you hit the accelerator. But I am not sure if the Prius Prime can even shut the engine while driving and simply use the momentum or traction motor to keep the car at speed.

    Anyone know more about this?
     
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  2. jaqueh

    jaqueh Active Member

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    Check this out.
     
  3. Spidey71

    Spidey71 Member

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    I've only got about 500 miles on my PP but I believe the Hybrid system does charge while driving in order to run in EV mode even after the main battery is depleted. This typically happens down hills or at lower speeds when the ICE isn't required to maintain speed. The difference I noticed is that while driving on an actual charged battery, the green car icon is approx. 20% larger, and when going into EV on the HV system, the icon is smaller.

    Other more experienced users - please correct me if I'm wrong!
     
  4. PT Guy

    PT Guy Senior Member

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    Yep.

    Every time the brakes are used or the car coasts in D or B some power is being put into the battery. The system knows when it can use electric drive and shut off the engine. The battery capacity indicator will show nothing, ----%, but there's enough power in there for some limited driving. I'm not sure if the engine does any charging of the battery in normal HV mode.
     
  5. Witness

    Witness Active Member

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    If I understood you correctly, the answer is YES. It happens often during my drive, usually cruising on a slight downgrade and I'm not trying to go any faster. This is noted by the EV indicator while I'm in HV and I'm within the EV brackets. The gears for the engine (for a lack of better description) are still engaged since you're in HV and you'll feel the switch from EV to ICE when you accelerate beyond the EV threshold/rate of acceleration. Most of the time I just let it do its thing, but sometimes I'll negate the switch simply because I'm trying to conserve some battery for future use.

    On a related note as you are learning about the Prime, you get less coasting resistance going down a long downhill when you switch to EV and in both cases adjust the throttle to keep the EV/Charge indicator at zero - neither using EV or regen. Basically, Neutral without being in neutral. That's because those aforementioned gears for HV have been disengaged.

    There are many others here with a lot more technical knowledge, so please correct me if I'm wrong. This is how I understand it after driving my PiP for the last five years.
     
  6. bisco

    bisco cookie crumbler

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    momentum won't keep a car at speed, unless the grade is steep enough. and if you're driving hv, you've told it not to use too much battery. the engine will come on as necessary to your accelerator pedal requirements.
    that's why it has an engine, there is no such thing as all engine driving(except for short durations) however, there are times when it neither uses the engine or battery.:)
     
  7. heiwa

    heiwa Active Member

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    Even at HW speed, Prime shuts off ICE when loard is low enough such as flat terrain with tail wind, almost undetectible slight decline, etc. When you are in HV mode with some EV range left, Prime is in charge sustain mode, maintaining the EV range you had it left. However, Prime often uses part of the EV range (about half a mile or a mile of the remaining EV range) to run on EV when the situation permits. It will charge back up to the range automatically and repeat this cycle as it sees fit. Set your DRCC at your desired speed and let it do the driving. It hypermiles better than I do.

    Posted via the PriusChat mobile app.
     
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  8. leaftoprius

    leaftoprius Junior Member

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    Great to know. Then can I infer that the system knows to take into account the optimal operating temperature of the engine? i.e. it will not shut it off prematurely or for too long that it goes below the optimal temperature? If so, that is pretty smart and sophisticated.
     
  9. huskers

    huskers Senior Member

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    It is the beauty of this car.
     
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  10. bisco

    bisco cookie crumbler

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    yes, while not perfect, the system takes most everything into account, and operates to produce the least amount of pollution possible. mpg's are just a side benefit.
     
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  11. john1701a

    john1701a Prius Guru

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    Watch the following video for some extreme detail about what really happens behind the scenes...



    On the left what we all see when driving a Prius Prime. That % value for the battery shows you the range available for EV driving.

    On the right is a phone-app I used to capture info you don't normally get to see, like % of the actual capacity for the battery. Keep in mind there's a buffer at the top & bottom for longevity, as well as HV driving.

    To answer the question of this topic, watch the RPM for the gas engine. It does indeed shut off while you are cruising along in hybrid mode.
     
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  12. A Prime Factor

    A Prime Factor Formerly "I want my PHEV"

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    Bring up the energy screen. It has a diagram with colored arrows that shows where the energy comes from and goes to. This will tell what is happening while you drive.
     
  13. Dudley1030

    Dudley1030 Active Member

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    When you run out EV mode there is about +-13% charge left in the battery. It charges as you drive like others have mentioned above. The ICE shuts off intermittently when there is enough charge to run the EV and the load isn't too high to need to ICE. The flatter the road and less need for acceleration, the more likely to run on more EV only when you are in hybrid mode. I've seen mine get down to about 10-11% state of charge before it kicks back to the ICE. I use a Scangauge2 to monitor more than the dashboard allows. It's very interesting.
     
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