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How much gas does it use to warm up the ICE?

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by usbseawolf2000, Dec 7, 2012.

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  1. usbseawolf2000

    usbseawolf2000 HSD PhD

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    I have wondered that before purchasing my PiP and I am sure there are many others in the same boat as me.

    I figured out a way to measure it. PiP provides a summary of the trip every time you turn off the car. It has the number of miles traveled and MPG for that trip. Pure EV trips will show 999 MPG.

    In order to measure gas consumption during my usual 2.0 miles trip, I forced the gas engine to start by turning on the heater. I immediately turned it off and let the ICE complete the warmup process. Once the engine coolant reaches about 130 deg F, ICE turned off. At the end of my 2 miles trip, I got 68 MPG.

    2 miles / 68 MPG = 0.0294 gallons = 111 ml

    Another data point is a 12.9 miles highway trip. I drove 12 EV miles before ICE kicked in. ICE was warming up for the last 0.9 miles and shutdown (reached 130 deg F) before I rolled into my garage. On that trip, I got 369 MPG. I also noticed the battery state of charge raised from 23% to 25%.

    12.9 miles / 369 MPG = 0.035 gallons = 132 ml

    To put the amount of gas used in perspective, I thought of using everyday household items to compare with. Inspired by the picture of the Power Split Device next to a soda can, I came up with this.

    Two jumbo eggs are ~140 ml.

    140ml 2 Jumbo eggs.jpg
     
    #1 usbseawolf2000, Dec 7, 2012
    john1701a, mnml, lensovet and 4 others like this.
  2. usbseawolf2000

    usbseawolf2000 HSD PhD

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    There is a way to reduce the amount of gas used further, by entering the ECO mode. In that mode, ICE should shutdown at 110 deg F.
     
    #2 usbseawolf2000, Dec 7, 2012
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  3. bisco

    bisco cookie crumbler

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    i also have been wondering this. some have said 1/50 of a gallon per mile, but this doen't work on a cold ice. i'll have to give it a try. thanks usb!
     
    #3 bisco, Dec 7, 2012
  4. Big Dude

    Big Dude Member

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    I assume the lower the external temperature, the longer to complete the warmup. The coolant requires more calories and more calories are simultaneously lost through the radiator (unless the thermostat totally blocks circulation). I suspect the real answer to your question will require an ambient temperature factor.
     
    #4 Big Dude, Dec 7, 2012
  5. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Yea, that's a great point. I parked my car in a warm garage so it starts out around 70 deg F. That 12.9 miles trip was driven in low 40's outside temp.

    If you guys have more data, please post. It'll be interesting.
     
    #5 usbseawolf2000, Dec 7, 2012
  6. jmlarence

    jmlarence New Member

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    Great stuff usbseawolf2000. Logged in just to say "thanks!" Have been wondering about that consumption for the past week.
     
    #6 jmlarence, Dec 7, 2012
  7. lensovet

    lensovet former BP Brigade 207

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    Well, that completely removes any qualms i had about flooring the car in EV mode, i guess. lol.
     
    #7 lensovet, Dec 7, 2012
  8. Adam Leibovitch

    Adam Leibovitch Member

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    The car is much more enjoyable to drive in floored EV Boost mode. Its worth every milliliter.
     
    #8 Adam Leibovitch, Dec 7, 2012
  9. bisco

    bisco cookie crumbler

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    i went out for a test drive tonite. fully charged battery, 45 degrees out, light rain/mist. headlites on, no heat, etc.
    drove 7.2 miles on ev, went into store for 10 minutes. came back on ev until the ice kicked at 12.4 miles. ice ran for 2 miles and shut off. got home at 14.4 miles. 326 mpg over 14.4 or 162 mpg over 7.2 on the return when the ice ran. using above calculation, 14.4/326 = .04417 7.2/162 = .0444 so it looks like the ev miles affect gas quantity equation?
     
    #9 bisco, Dec 8, 2012
  10. Adam Leibovitch

    Adam Leibovitch Member

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    Hi. So did you drive while the ICE was warming, or you waited until after the ICE was done warming before you started the trip?
     
    #10 Adam Leibovitch, Dec 8, 2012
  11. usbseawolf2000

    usbseawolf2000 HSD PhD

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    I drove while ICE was warming up for that 2 miles trip. The route has red lights and stop signs.
     
    #11 usbseawolf2000, Dec 8, 2012
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  12. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Bisco, i wouldn't worry about 2 microliter difference.
     
    #12 usbseawolf2000, Dec 8, 2012
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  13. bisco

    bisco cookie crumbler

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    so, .045 is about 1/25th of a gallon or about 50 mpg?
     
    #13 bisco, Dec 8, 2012
  14. retired4999

    retired4999 Prius driver since 2005

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    :D
     
    #14 retired4999, Dec 8, 2012
  15. Adam Leibovitch

    Adam Leibovitch Member

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    Thanks I was wondering if the driving could be what accounted for the differences. But I should have measured my coolant temperature, thats an important input it seems. Probably why I was 0.035 and bisco was 0.044, my car had been parked outside in high 50 to low 60 degree temperature.
     
    #15 Adam Leibovitch, Dec 8, 2012
  16. bisco

    bisco cookie crumbler

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    my ice comes on for 2 miles on my commute, if i don't charge at work. that would be one gallon every 5 weeks!
     
    #16 bisco, Dec 8, 2012
  17. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Bisco, 2 miles / 0.0442 gallons = 45 MPG. Do you know the battery SOC betore you shut it down? EV mode ends at 23% so extra energy might have went into the battery.
     
    #17 usbseawolf2000, Dec 8, 2012
  18. bisco

    bisco cookie crumbler

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    the hv portion was about half full or 5/8. the ice was off when i pulled into my garage.
     
    #18 bisco, Dec 9, 2012
  19. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Ok, so you used some of the HV portion.:)
     
    #19 usbseawolf2000, Dec 10, 2012
  20. SageBrush

    SageBrush Senior Member

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    Bob Wilson figured out the warm-up fuel consumption by the ICE in his G3 Prius; I imagine the same for the PiP. I have always thought the tricky part is taking into account that fraction of ICE energy that ends up in the battery, but I trust that Bob took that into account.

    I suspect USB would end up with a more accurate result if he:
    1. Started a drive from a full charge;
    2. Forced an ICE warm-up after a couple of miles of EV driving (so that there is room);
    3. Drove until EV was depleted and the Prius decides to turn on the ICE
    3a. Stop the car at (3) and calculate.
     
    #20 SageBrush, Dec 10, 2012
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