Double Tank Mileage Contest

Discussion in 'Local Clubs, Events, and Road Trips' started by bwilson4web, May 4, 2014.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Thanks! I wanted something that would have some merit, require no special route or rally staff, and be open to all Prius models. It also has to be achievable but only at significant effort.
    I think I did:
    • true_gallons = indicated_miles / indicated_MPG :: the error is in the tire revs/mile of the tires (*)
    • maximum tank capacity is the limit in the table . . .
      • no need to run out of gas (something I don't care about)
      • no need to overfill a tank (what scares me!)
    Now there is a cheat, to claim a larger diameter tire. But the requirement to document the tire calibration offset with GPS or mile marker vs. tripmeter makes that a harder fake.

    Bob Wilson

    * - I have gone through four distinct tire sets in the 2003 Prius in my 110,000 miles and 9 years and due to an unfortunate pair of punctures, our second set on the 56,000 mile, 2010 Prius, in 5 years. I've also run the tank dry about 30 times in the 2003 Prius and about 6 times in the 2010 Prius so I know their true tank capacity. What I found is the relative 'rev/mile' determines the indicated MPG accuracy and nothing else.
     
  2. SageBrush

    SageBrush Senior Member

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    I was unaware. That is very good to know, and nicely explains the grouped biases in fuel economy inaccuracy reported in the forum. Thanks
     
  3. bwilson4web

    bwilson4web BMW i3 and Model 3

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    2014/09/01

    By example, here is a GPS record along with tripmeter value:
    [​IMG]
    76.1 / 72.3 = 105.26% :: the calibration factor between true and indicated miles.​

    That was several hours before this image when I returned home:[​IMG]
    • 390 miles_indicated / 71.9 MPG_indicated = 5.42 gallons true
    • 105.26% * 390 miles_indicated = 410.5 miles true
    • 410.5 / 5.42 = 75.7 MPG true
    • 11.9 - 5.42 = 6.48 gallons remaining
    • 6.48 gallons * 75.7 MPG = 490.5 miles remaining
    • 410 + 490 = 900 miles total at this rate << 976 miles goal <gerrrr>
    Bob Wilson
     
    #23 bwilson4web, Sep 1, 2014
    Last edited: Sep 1, 2014
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  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    2014/09/02

    [​IMG]
    • 478 miles_indicated / 73.6 MPG_indicated = 6.49 gal true
    • 105.2% * 478 miles_indicated = 502.9 miles true
    • 502.9 miles / 6.49 gal = 77.5 MPG true
    • 11.9 - 6.49 = 5.41 gal remaining
    • 5.41 mi * 77.5 MPG = 419.3 miles remaining
    • 419.3 + 502.9 = 922.2 miles projected
    This is a pattern I saw last year of increasing performance during the endurance test. This leads to a decision point:
    1. Restart the stunt drive using the 'lessons learned'
    2. Continue and see if the improving performance will meet the goal, 2x an EPA tank.
    If I were doing this just for show, I would "restart;" put the trophy on the shelf, and; 'turn the air conditioner back on.' But I am curious to find out how close I can come but also confirm my earlier metrics of 11.9 gallons of usable fuel in the 2001-03 Prius. The only wild-card is I have a pair of Yokohama tires I need to test in the remaining 23 days of their return policy.

    I am very confident the oversized, Yokohamas will work on the front wheels and +90% confident they will work on the rear wheels. The next smaller size will easily fit but the revs/mile is ~2% higher (i.e., less overdrive.) Also, I've got good GPS calibration data on the existing tires and suspect their pressure has fallen off a little. This is a great time to 'tickle the tiger' and measure the effects of tire pressure and rolling drag.

    Bob Wilson
     
  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Not every test is a success and right now:
    mi MPG true G true mi true MPG last MPG trend MPG proj miles
    1 159 68.0 2.34 167.3 71.5 71.5 71.5 851.3
    2 205 69.7 2.94 215.7 73.3 80.3 80.3 934.7
    3 238 70.2 3.39 250.4 73.9 77.3 79.0 922.6
    4 307 70.8 4.34 323.0 74.5 76.7 77.9 912.4
    5 390 71.9 5.42 410.3 75.6 80.3 78.7 920.2
    6 478 73.6 6.49 502.9 77.4 86.5 80.7 939.3
    7 507 73.8 6.87 533.4 77.6 81.3 80.8 939.7

    I will come in ~35 miles short of the target goal, 976 miles. I burned too much gas in the first, 168 mile, segment. Poor technique probably accounted for the rest:
    • Warm-up and hybrid mode - I didn't really start doing it right until the last segment.
    • Better loop - I have a 3.5 mile loop that work very nicely and a Baily Cove Rd segment.
    • Finer speed control
      • 24 mph for cruise control set speed
      • 18 mph, peak range speed, for 1/4 mile sections
      • 15 mph for rolling turns
      • 12 mph to approach red light so it changes to maintain momentum
      • <24 mph cresting a rise so downgrade reaches 24 mph, not exceeds it
    So tonight, I'll run the car far enough to get the indicated miles over 500 for the "Top 20" list and start the Yokohama tire testing tomorrow.
    [​IMG]
    • 507 mi / 73.8 MPG = 6.87 gallons true
    • 105.2% * 507 mi = 533.4 miles true
    • 533.4 / 6.87 = 77.6 MPG true
    Once I'm sure the new Yokohama are working, I'll restart the test paying closer attention to the early segments. The Yokohama's should be slightly slower turning than the worn-out Sumitomo T4s. This should improve MPG along with practice improved, speed management skills in all segments. I would love to do 1,000 miles in the 2003 Prius on one tank but that is in the 'play the lottery' odds of happening.

    Bob Wilson
     
    #25 bwilson4web, Sep 3, 2014
    Last edited: Sep 4, 2014
  6. SageBrush

    SageBrush Senior Member

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    Announcement

    I'm game for the 500 mile stunt
    Stock Prius v(agon) 20 months old, 54k miles on the odometer. OEM tyres at sidewall max pressure

    Geography: SW Colorado, about 6000 ft elevation with gently rolling hills
    Strategy: Either next week or the week thereafter I have a 5 day window I don't have to drive highway speeds. I'll drive ~ 100 miles a day split into two sessions of ~ 50 miles each. The route is mixed residential and rural, 8 miles each way, 95+% below 45 mph and "P&Gable."

    PENDING:
    10 mile drive to calibrate distance meter
    32 mile drive later today to check that my fuel economy is within spitting distance of the double-EPA goal
     
    #26 SageBrush, Sep 3, 2014
    Last edited: Sep 3, 2014
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  7. SageBrush

    SageBrush Senior Member

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    I started out too late in the evening, so I only drove 16 miles.

    Prius.1.png

    I'm reasonably happy with the result, although it includes a couple of items for and against:
    1. 2-3 bars of battery SOC were lost from start to finish (negative)
    2. The car had a bit of warm-up before I took off as I looked for an open door. I zeroed the meter just before I started to roll (negative)
    3. I expect the actual MPG to be about 5% lower after distance calibration (negative)
    4. Headlights were on (positive since I will not use them in daily driving. ~ cancels (3)
    5. My technique was sub-optimal (positive I hope)
    6. 3/4 of my 16 mile routes will be with a pre-warmed engine (positive, more than cancels (2)
    So all in all the trial run confirms that 84 MPG is reachable, and I hope for a bit more. 90 MPG seems out of reach. An aside: I've picked my route because it does not have much traffic and so brake use is minimal and I can coast to STOP signs. OTOH, the roads are rather poorly maintained and bumpy, so fuel economy in the mid- high 80s is I think quite an achievement for a Station Wagon ;)
     
    #27 SageBrush, Sep 3, 2014
    Last edited: Sep 3, 2014
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  8. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I have no problem with the car being throughly warmed up before resetting the trip meter. After 500-1,000 miles spanning multiple days, that first warm-up 'fades into the noise.' <grins>

    Bob Wilson
     
  9. SageBrush

    SageBrush Senior Member

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    I started a run yesterday -- 64 miles. I have a 9 day vacation so I'll likely finish off 600 miles to get into the record book. 1000 miles is too much work for my lazy self. Note that the numbers in this table are PRE correction for display inaccuracy. I'll calibrate by mileage markers at the end of the marathon.


    Date am/pm CUM MPG Odometer Trip MPG Temperature (F) Day MPG
    1 10/2/2014 am 81 16 81.00 63
    2 85 32 89.42
    3 85 48 85.00
    4 86 64 89.15 86
     
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  10. SageBrush

    SageBrush Senior Member

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    After a 2 day hiatus, I sat my butt down and drove for 4 hours. That really is my limit -- T-shirt or not.
    The first 16 miles were (relatively) terrible, so I spent the rest of the afternoon clawing it back. I was worried that today's wind would be my undoing but it either did not matter, or the wind was offset by a warmer day. I tend to think the latter is true.

    Today I parked in a part of my driveway where the sun tomorrow will not be shaded; and I might 'cheat' a bit by opening the hood an hour or two before my drive to 'pre-heat' the engine.

    Date am/pm CUM MPG Odometer Trip MPG Temperature (F) Day MPG
    1 10/2/2014 am 81 16 81.00 63
    2 85 32 89.42
    3 85 48 85.00
    4 86 64 89.15 86
    5 10/5/2014 pm 83.7 80 75.61 68 - 74
    6 84 96 85.53
    7 84.5 112 87.63
    8 85 128 88.67
    9 85.1 144 85.91
    10 85.6 160 90.38
    11 86 176 90.22
    12 86.3 192 89.74 86.4
     
    #30 SageBrush, Oct 5, 2014
    Last edited: Oct 5, 2014
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  11. 2009Prius

    2009Prius A Wimpy DIYer

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    For gen 2 Prius 2X EPA would be 92 MPG. During the 3 summers when I had the leisure to commute via back roads at speeds between 25 and 40 MPH, there was only one tank that by chance (noise) went above 90 MPG (real calculated MPG, not MFD MPG which is too optimistic as shown in the data below). Now I no long have the leisure but even if I did, it would be hard to achieve - for me at least.

    [​IMG]
     
    #31 2009Prius, Oct 5, 2014
    Last edited: Oct 6, 2014
  12. bwilson4web

    bwilson4web BMW i3 and Model 3

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    This is not a trivial challenge but it can be achieved.

    Bob Wilson
     
  13. 2009Prius

    2009Prius A Wimpy DIYer

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    Yes if one could afford the time to drive around at 20 MPH then it is easily achieved. Best wishes to all contestants.
     
  14. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Actually 25 mph will do and the patience to handle warm-up. It was never ment to be easy.

    Bob Wilson
     
  15. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I'm trying to reconcile that with the requirement to drive 1904 kilometers (1190 miles) without refueling. Why not just set a target around 800 km's (500 miles)?
     
  16. SageBrush

    SageBrush Senior Member

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    My average speed starts fresh every time I shut down the engine, but the times I have looked I have seen 29 mph. I'm not saying that is optimum, only that it is ~ consistent with being competitive in the challenge.
     
  17. SageBrush

    SageBrush Senior Member

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    Another day at the wheel; my wife is giving me funny looks.
    Once again, the first 16 miles drops the average quite a bit, and I spend the rest of the day getting it back. Today was warmer than yesterday, the car was in the sun, AND I popped the hood for sun engine sun-bathing two hours before I took off. What can I say -- the warm-up penalty is hard to avoid. Pre-calibrated MPG is now 86.7 after 302 miles, up from 86.3 yesterday.

    Since the inline table is getting too long, here is a link to the table as a Google sheet. Below is the data in a pretty graph.

    Sagebrush 10-6.png
     
    #37 SageBrush, Oct 6, 2014
    Last edited: Oct 6, 2014
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  18. SageBrush

    SageBrush Senior Member

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    Refuel all you want, just do not reset the trip meter.
     
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  19. Mendel Leisk

    Mendel Leisk Sand Pounder

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    The Toyota block heater will help some. With 2 hour use, and ambient temps around 20C you'll start off with coolant temp around 40C, climbing to 50C within a block or two, once it homogenizes. Obviously the engine itself is warming, but the BH does jumpstart the process.
     
  20. SageBrush

    SageBrush Senior Member

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    That would really be cheating, but outside of this competition it is a good idea. And now that I think of it, I probably should have attached my scangauge for temperature monitoring and blocked the engine radiator air intake vents.