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Uphill vs. downhill makes the biggest difference

Discussion in 'Gen 3 Prius Fuel Economy' started by PriusRos, Aug 29, 2009.

  1. fuzzy1

    fuzzy1 Senior Member

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    This helps explains much of the difference. A US Gen3 is much heavier than your Gen2 was, and I'm not as skinny as you. Neither is my wife. Including some equipment, my car weight for this trip was probably about 1560 kg.

    This is becoming more solid than my original 1 gal / 10,000 feet rule of thumb. I'll try to take more data on an upcoming vacation with considerable altitude change, but it will be a loop, not an out-and-return trip, so any figures will be harder to interpret.
     
  2. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Prius can climb hills easy due to the huge MG2 torque. See the video below of me climbing with my wife in the passenger seat. Yes, the speed is low but so is the engine RPM (about 1,500). HSD was working like a series hybrid (such as Volt). Gas engine was making power to feed to the electric motor to get a huge torque boost. A step gear car will not be able to do it.


    Below is the slope of the hill in the above video:
    [​IMG]

    In the video below, a friend with 1996 Civic and I (with 2006 Prius) experimented with hill climbing. Although the Civic is much lighter, the engine almost stalled when the RPM gets as low as my Prius.



    To highlight the benefit of the synergy between gas and electric, I am going to compare and contrast the two:

    Column 1 Column 2 Column 3
    0 Prius Civic
    1 ICE Displacement 1.5l 1.6l
    2 ICE Torque 82 lbs-ft 105 lbs-ft
    3 ICE Power 76 hp 106 hp
    4 Total Power 110 hp 106 hp
    5 Car weight 2 900 lbs 2 300 lbs
    6 Passenger Volume 96 cu.ft. 90 cu.ft.
    7 Cargo Volume 16 cu.ft. 12 cu.ft
    8 Combined FE 46 mpg 31 mpg
     

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  3. fuzzy1

    fuzzy1 Senior Member

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    I'm missing something.

    First, a caveat. Normal pictures are terrible for showing me steep slopes, the camera view tends to flatten perceptions.

    The first video claims the hill has a 15-20 degree slope. But the ground lines on two foundations measure out on my display as 16 and 17 %, which convert to between 9 and 10 degrees, much less steep than advertised.

    Your graph appears to have a rise of about 120 feet in 0.2 mile, a slope of only 11%, or 6.5 degrees.

    These numbers are not particularly steep. What am I missing?
     
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  4. usbseawolf2000

    usbseawolf2000 HSD PhD

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    The graph should be more accurate as it came from using this tool.

    The 15-20 degree was my guess when I edited that video and I am surprise I was way off. From what you saw in the video, does it look like 6.5 deg angle hill?
     
  5. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    100_2968_1MinCons.jpg
    Here's a typical Consumption display readout for my area. I took this particular snapshot last night at the end of a 450-mile drive, so the average mpg is higher than my usual commuting average. However, what is typical is the big variations in the 1-minute readings. The 50-plus to 100mpg readings are when I am going downhill while the 35 to under-50 mpg readings are when I am going uphill. It's almost like an inverted pictures of the hills themselves :D !
     
  6. Ceczech8

    Ceczech8 New Member

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    Hi all, First post!

    Anyways, I am still on my first tank of gas (just bought the car 11/9/09) and have a "lifetime" average of 46 mpg. I thin that is somewhat typical for what I drive in a day.

    55 mile commute to work on a 1000 ft difference (Start high and go low, then reverse it back home)... To work I average 51.3 mpg. To home I average about 43. My total average is about 46.6. I think it will get better once the car/motor is broken in more. The hills and mountains on the PA interstates is what kills the mpg.
     
  7. LakePrius

    LakePrius Special member

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    I've done a bunch of round trips in my 2010 of 300-400 miles. The first 70ish miles are pretty much downhill - from 10,000 feet to sea level. Over this first part I tend to get about 92-93 MPG. By the time I hit 150-200 miles, I'm down to about 65 MPG and then into the mid 50's on the return trip before I start back up the hill. By the time I'm home I've averaged 52-53 MPG over the entire distance.

    This is about the same MPG I get just driving around town without a lot of concern about driving style - but still taking opportunities to make the instantaneous gauge hit 100 when possible.

    So my experience is in the end it all just seems to average out to about the same thing.