Uphill Strategies

Discussion in 'Gen 3 Prius Fuel Economy' started by Erikon, Apr 8, 2010.

  1. Erikon

    Erikon Active Member

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    I have to tackle two hills during my regular commute and I was just curious what strategies PC folks have found that might work best!

    The first hill is a moderately steep one mile climb with a 45mph limit and I usually have traffic behind me, so there's not much I can do here, except when I get stuck behind a truck. I find when allowed to make this climb at 25-30 mph it can boost my mpg for that trip to 70!:D

    The second hill is the killer! It starts after turning left at a light, so no chance to build up speed, and is mild enough to begin with that I can go the first 20 seconds on EV. Then it gets steeper and steeper till I pretty much have to drive more than half the distance red lined! It takes about a minute and a half to get to the top at 30mph.

    Would it be more efficient to just get up this hill as fast as safely possible to cut down on the time I'm spending on it, since the ICE is gonna be running hard anyways?
     
  2. vday

    vday Member

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    I have a big clib of about 5 miles 8 klm. non stop at various degrees.
    Kills my MPG:mad:
     
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  3. qbee42

    qbee42 My other car is a boat

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    No matter how you attack the hills, your ICE is going to provide the power. Given that fact, you want to run your ICE in the most efficient manner, which usually means fairly hard but not wide open throttle (WOT). I don't know the range of the sweet spot for a Gen III, but the best general advice is to put your foot into it and get it over with, but try to avoid WOT.

    Tom
     
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  4. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Minimize accelerator pedal movement. Every time you move the pedal, the computer has to figure out the most efficient ICE RPM (although this happens in split second). Push the pedal and keep it at steady state.
     
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  5. Tom183

    Tom183 New Member

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    The key is keeping the ICE at the most efficient RPM.

    At slow speeds, that means hard acceleration. At high speeds, it means a lot less.

    Your first hill is a classic example - you have to hit the gas pretty hard to keep climbing, so at 30mph you're still in the right RPM zone, but at 45mph you go into the red.

    For your 2nd hill, get on the gas sooner and try to build some speed while it's not as steep, then ease up as you reach speed. Then try to hold it a little lower until you're over the top even if you lose speed in the process.

    Do NOT use EV - that just drains the battery, then the engine has to work harder to replace the charge.
     
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  6. john1701a

    john1701a Prius Guru

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    Take advantage of the engine.

    Get up to the desired speed quickly, brisk not aggressive.

    With the engine at a higher but steady RPM, it will find an efficient operating state and use the excess power created to top off the battery. It may appear that the climb is inefficient, but you'll end up better off overall. That's the beautY (and a big difference) between a FULL hybrid and an ASSIST.
    .
     
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  7. JasonPro

    JasonPro Junior Member

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    I have a few hills and a stretch of highway driving on my commute. My strategy is to plan ahead for areas where I know the ICE will have to run either due to the hill or highway and try to use up the battery as much as possible before these areas. This strategy has yielded the best results for me. I definitely agree with the notion of using the ICE to get up to speed and use the EV for sustaining speed.

    I realize that blindly using EV as much as possible doesn't yield the best mileage and that the prius computers figure out the best instantaneous thing to do for the best MPG. However, the prius is not going to be aware of upcoming driving conditions that will either be great for a long stretch of EV or great for charging either by a long downhill or ICE run.
     
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  8. Erikon

    Erikon Active Member

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    Yeah, the good thing about these hills is going back down them!:p I can glide for a big chunk of my commute, then charge back up when I go downhill. Hmmm, if I could find a route where I can always go downhill, never up, that would be the best solution!:D
     
  9. usbseawolf2000

    usbseawolf2000 HSD PhD

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    If you can glide with ICE off, you will get double the climbing MPG. For example, if you climb at 25 MPG and back down with ICE off, you should average 50 MPG.
     
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  10. spiderman

    spiderman wretched

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    Try different things and report back on the effect. Keep really good records (temp, rates, pedal position, etc). It will help us all.
     
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  11. Erikon

    Erikon Active Member

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    This Sunday is supposed to be around 60 degrees and nice. I'll see if I can take a few runs and try different things. Some baseline facts: Car still has a half tank of winter gas. Tire pressure 42 front, 40 rear. Grill blocked 75%.
     
  12. Erikon

    Erikon Active Member

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    Okay, did three runs and this info covers the distance between the light at the bottom of the hill to the crest. Temp around 60 degrees, sunny and dry. MPG's from display.

    Run #1: Kept the HSI bar a little below the power zone, still in the "sweet spot", speed reached 37 MPH. As speed fell to 30, I depressed the pedal to maintain 30 MPH and spent about 15 seconds in the red till I crested. MPG was 24.9.

    Run #2: Kept the bar below the midpoint so I glided as far as possible, reached 32 MPH, then switched to the technique in run #1. At the crest MPG was 28.9.

    Run #3: Went up the hill at 40 MPH, half the climb was in the red and crested at 19.2 MPG. Shaved maybe 20 seconds off the climb.
     
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  13. gazz

    gazz Member

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    In run 2 what do you mean by "glided"?
     
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  14. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Sorry to break this to you...

    The faster you climb the hill, the less MPG you gonna get. It goes the same to slower climb (higher MPG). You'll need to perform those tests at the same speed if you want to compare.
     
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  15. qbee42

    qbee42 My other car is a boat

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    Remember when comparing techniques that the Prius does *not* factor the battery SOC into mileage calculations. If you start at the bottom of the hill with a full battery and finish with an empty battery your MPG will look better than it really is.

    This is what causes many Prius drivers to obsess about EV mode. It looks like you are getting fantastic mileage, but it's just an artifact of the mileage calculation.

    Tom
     
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  16. Erikon

    Erikon Active Member

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    Oops, meant stealth! I always confuse the two.

    I was more interested in keeping the car in the Eco range for as long as possible. If it briefly gets up to 37 then that's a little momentum to stave off the inevitable trip into the power zone!

    I understand not using the EV to the point where the ICE has to kick in to recharge. I think that's only happened to me once during a long residential area drive with a 25 MPH speed limit! Not much I could do to avoid it. However, I normally get this energy back from riding the brakes on the downhill side of my commute!:D
     
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