The hill from HELL!!!

Discussion in 'Gen 2 Prius Fuel Economy' started by nooaah, Sep 23, 2008.

  1. PaulHS

    PaulHS Member

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    I can't tell whether you're attributing mpg gain from increased tire pressure or alternate routes, or both. But increasing my tire pressure yielded an average increase of 4 mpg, for what it's worth.

    What surprises me the most is how rainy weather negatively affects mpg. Whereas I can usually eke out a couple tenths of an mpg increase per daily round trip to and from work on clear, dry days, with wet roads there's a net loss of a couple tenths.
     
  2. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    well, if you are like me, there is no way to avoid the elevation change, so learn to drive the hill better. go down as SLOW as possible (ya slow, this increases your regen)... you might find another route that is not as steep, but if its longer, you waste gas (you might get better gas mileage, but is that what you really want?) and in real terms, its the elevation change that matters.

    so is it better to get it over with in a shorter period of time? or climb slower over a longer time period. well, elevation is more important, but distance still plays a part.

    look at routes that are not as steep...can you justify that route by businesses that are on that route? if so, it might justify the extra distance...imm, terrain is what you bought into when you decided to live where you live. sure the top of the hill is where everyone wants to be...it always feels better to look down on others, etc...
     
  3. dwreed3rd

    dwreed3rd New Member

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    First off, we don't have our Prius yet. This is from what I read here on PC.

    Since "the pulse and glide" goes against the basic laws of thermo dynamics. I.E. It should be more efficient to power the car directly with the ICE than use the IE to charge the battery to power the MGs to power the car, due to the efficiency loss. In other post I've read that the benefits of the "pulse and glide" technique can vary due to driving conditions. Therefore my assumption is that, while everything that you say is true in normal circumstances, the Prius' regenerating MGs may be more or less efficient depending on the characteristics of the different routes. The only way to know for sure is test the different routes and determine gallons used for each senerio. Like you implied, a lower mpg could be less efficient if the mileage is longer thus ending up using more fuel. If it's not a reading on the MFD, or you do not have an SGII, dividing MPG by miles driven will give you gallons used. What you are looking for is least gallons used for the route. This then can be weighed against travel time and comfort.

    Good Luck.
     
  4. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    efficiency when using gas or batteries or both DEPENDS... and terrain along with speed is the prime determining factor...

    on flat ground, it is more efficient to never use the batteries because there is some conversion losses, but the engine in the Prius is not designed to provide the motivating force in all scenarios thus requiring the battery's help when accelerating and any hill requires continuous acceleration to maintain a constant speed because negative gravity must be overcome.
     
  5. nooaah

    nooaah New Member

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    Well, here's the thing. I climb the awful, steep hill and then I go down a bit. The new route I take runs parallel to the road I need to get to at the top of the hill and I can effectively P&G there. When I hit the new hill, I actually have a shorter distance to go up without and stops to the top. It's the same distance between the two. :)

    Oh, and I was attributing my gains to the better tire pressure and only a little to the new route since it's only about a mile or two of my average commute. The new route also allows for a nice regen and about a mile long, uninterrupted glide on the way home. I haven't done that yet since I haven't gone directly home from work in about a week, but I think it will help my mileage once I do. Again, near-equal distance (perhaps a shorter distance, I'll have to measure) so the gas consumption should be similar, as well.

    I think I've stabilized at 56 mpg now. I'm pretty happy with this car!
     

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  6. C12H23

    C12H23 Junior Member

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    Get out and push :D:D:D:D:D
     
  7. Rxmxsh

    Rxmxsh Member

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    Interesting thread. I also have steep ride home from work. To work, I get about 60-80mpg's, depending on drive style. On the way back, I get about 27-35. I only have one question - someone mentioned using google maps, terrain mode - how does that help? I'd like to find the elevation of my route.

    Great thread!
     
  8. dwreed3rd

    dwreed3rd New Member

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    The terrain may be flat but if there is alot of stop and go bumper to bumper traffic from one stop sign or traffic light to the next, I would think the use of batteries could capture and reuse some of the energy used in the braking.
     
  9. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    stop and go traffic can be more difficult than terrain simply because its uncontrollable and unpredictable. a route with little or no stops, left turns or lights; even if slightly longer would be better for you in most cases.

    now if you can find that route (i use them ALL THE TIME) and its flatter, you have got it made

    stop and go does provide more regen, but remember regen efficiency is like 3 to 10%... so you will lose EVERYTIME
     
  10. dwreed3rd

    dwreed3rd New Member

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    There is no such route, unfortunately, during any of the rush hours in or around metro Atlanta. You can throw in sporting events and convention activities too, Braves, Falcons, Georgia Tech, World Congress Center, ETC.
     
  11. SageBrush

    SageBrush Senior Member

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    This entire story is not making sense to me, and I am no stranger to filling up the battery on downhill driving. More experience is needed to believe the mpg discrepancy. What is the hill's absolute elevation ?

    Anyway, some off the cuff advice:

    Coast up to stop signs on the incline.
    Reach the top of the hill with a depleted battery.

    Good luck !
     
  12. nooaah

    nooaah New Member

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    the hill is 10% grade. You can't really coast at any point besides the 10 feet right before the stop sign. Hell, I'll take a video tomorrow so you guys can appreciate this thing's awfulness.
     
  13. SageBrush

    SageBrush Senior Member

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    Even better, how about an annotated Google map that includes stop signs ? That would be cool !
    How fast are you going when you apply brakes on the uphill ?
     
  14. abq sfr

    abq sfr New Member

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    You need to move someplace where you go downhill in the morning when its cold and your engine is least efficient, and go uphill in the evening when you're engine is warmed up. You think that hill is bad? When I drive to Taos there is a long curvy uphill grade north of Pilar (where the rafters get into the Rio) that sucks my traction battery down to 27%... that's down to a fractional bar you almost can't see on the display. At the top of that hill I see my instaneous mpg go as low as it can go, but you can maintain just about any speed you want even though it's almost 100% gas engine propelling you. Of course coming back down it is something else... 70-80% SOC. Round trip I get 57 mpg so I guess I can't complain though :D
     
  15. nooaah

    nooaah New Member

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    Sheesh, that's some hill you have haha.

    I ended my tank with 56.2mpg. Definitely nothing to complain about, but it gives me realistic hope that I am capable of getting over 60mpg when I move in a year or two (and choose a home that isn't at the bottom of an evil hill)!
     
  16. dwreed3rd

    dwreed3rd New Member

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    Perhaps you could find a parking garage with a car elevator to ride up and a ramp to come back down. :drum:
     
  17. drees

    drees Senior Member

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    Just for everyone to keep in mind - a NiMH battery's charge/discharge efficiency is only about 66%.

    This means that if you put 1000 w/H into a NiMH battery, you will only get about 660 w/H out of it.

    So at best, you can only recover 66% of the energy spent going up the hill when coming back down.
     
  18. dwreed3rd

    dwreed3rd New Member

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    Welcome back to the future. I had airless tires on my first bicycle as did many early cars, before my time. It's just that I tend to get a little suspicious when the performance promises appear to be in the form of hyperboles. I'm not from Missouri but I'll still wait to be shown or here other members confirm the claims.
     
  19. rondodog

    rondodog Junior Member

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    My fuel mileage is awful: most of my driving per day is a mountain pass. Up from the valley to the top of the pass, then down again. I don't gain a lot back from the downside because of L.A. traffic (if you don't keep up with the flow, you get cut-off or otherwise attacked by driving coasting down/driving slowly).
     
  20. JimboK

    JimboK One owner, low mileage

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