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ScangaugeII - uphill xgauge to monitor for best ICE performance

Discussion in 'Gen III 2010+ Prius Fuel Economy' started by walter Lee, May 15, 2011.

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  1. walter Lee

    walter Lee Hypermiling Padawan

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    What ScangaugeII xgauge should I be monitoring for the optimum fuel efficiency from the gasoline engine when I am going up hill?

    Setup: 2010 Toyota Prius III with ScangaugeII ( setting:AVG, GPH, RPM, Soc) . Yokohama Avid S33 tires set at 48 psi front, 44 psi rear .

    Driving environment: +3 miles of crowned Asphalt road with one lane in each direction. The road elevation is continously going uphill and downhill with grades ranging from about 10 to 25 degrees, each downhill and uphill grade is from 0.05 miles to .2 miles in length. There are no stop signs or traffic lights or speed bumps. This section of road is not very busy but the posted speed limit is from 20 mph to 35 mph and it has photo enforced speed cameras. Assume that there are no other cars on the road.

    Hypermiling Task/Challenge -- Doing a Pulse and Glide Cycle in continously hilly terrain with the ScangaugeII: For some of the uphill grades even if I increasing the Prius velocity to 12mph over the speed limit at the bottom of the hill -- if only the Prius electric motors are used I will lose 20mph in speed -- so normally I startup ICE before I reach the bottom of the hill use the ICE to push the prius uphill. I know that accelerating during the uphill grade will cause the Prius MPG to drop and that allowing the Prius to slightly de-accelerate by a few miles per hour will help keep the MPG up. Currently, I am trying to optimize the Prius ICE fuel efficiency during the uphill grade by keeping the ScangaugeII Xgauge GPH to between .80 and 1.20 during the uphill climb. However, this may not be the optimum power setting for going uphill. Is there a way to use the ScangaugeII to extract an optimal power output and fuel efficiency from the Prius ICE during an uphill climb?

    Example of my current technique: The speed limit is 35 mph. There are no other cars on the road at this time. I am in ECO mode. As I get to the middle of downhill grade I apply the accelerator so that the ICE is turned on by the time the Prius is at the bottom of the hill and the Prius is going about 40 mph. As the Prius goes uphill, the GPH is kept between .90 to 1.10. The Prius slows down by from about 40 mph to about 20 mph by the time I am at the top of the hill. If there are other cars on the road - I increase my speed at the bottom of the hill to 45 mph and when I get to the top of the hill I am usually running at 25 mph.


    Thanks

    Walter Lee
    2010 Toyota Prius III, Blue Ribbon, Dk grey, OEM floormats
    Yokohama Avid S33 (48/44)
    scangaugeII (AVG, RPM, GPH, Soc)
    11800 miles/ 58.7 mpg
    dc/md/va
  2. fuzzy1

    fuzzy1 Senior Member

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    Are you stating these slopes accurately, not interchanging degrees with slope-percents? 10 to 25 degrees means 18% to 47% grades, giving elevation changes of 180 to 490 feet in 0.2 mile. The higher slope is double the steepest paved segment I've heard about in this region, and is outright dangerous with any precipitation whatsoever.

    With slopes this steep combined with photo speed cameras, I think hypermiling is out of the question. A lot of energy must be burned off by friction brakes on the downslopes.
  3. mikewithaprius

    mikewithaprius New Member

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    OK, so sometimes we try to minimize engine-on time with a quick, efficient, pulse, then glide of some sort, whether regular or warp stealth.

    In this case, however steep the hill is, it sounds there's no choice but to run the ICE for a given distance, instead of time. This means keeping instant mpgs high as possible during that time. There are basically two choices:

    1. Keep speed up the slope but just maintain speed, don't speeding up. For this, just watch the instant mpgs on either Scangauge or the display. It really doesn't matter, the idea is just to see how little gas you can apply while keeping speed.

    2. For no-traffic situations where the following downhill will give you momentum to speed back up some, drive with load, meaning, again, just use the minimum amount of gas, but this time to slowly bleed speed to a target speed at the crest of the hill.

    Since you're already driving up a hill, it's going to be pretty efficient. Just focus on keeping the max mpg for either of those two options, you can't do much else.

    If I misunderstood the situation let me know, but sometimes you just gotta get up that hill!
  4. walter Lee

    walter Lee Hypermiling Padawan

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    I am not a civil engineer so my description of the downhill and uphill grades may need some tweaking. :rolleyes: The section of the road I am talking about is Muncaster Road in Montgomery County Maryland which starts at Maryland Route 108 (Olney Laytonsville Rd) and end at Muncaster Mill Rd (Md Route 115)/Redland Road. The speed cameras are on a flat section of the road near Granby between Artesian and Sunwood. The elevation changes when going from Rt 108 to Rt 115 ( up 10 feet until about Meredith Dr down 30 feet until Artesian Dr - flat road until about Sunwood Lane then down 40 feet to farm Park Access then up 60 feet until the last 60 feet of the road before it hooks up with Rt 115 - the last 60 feet of road drops about 6 feet in elevation before it connects to the intersection and it joins up with Rt 115 . Most of the section from farm park Access to Rt 115 has a 20 mph speed limit. When going from Rt 115 to Rt 108 after doing the 6 foot climb if I start a glide at 20 mph at the top of this grade by the time I reach the bottom of the grade at the Farm Park access intersection I am going 40 mph if I don't apply the brakes. Even if the Prius is going 40mph by the time it is at the Farm Park access intersection if I dont run the ICE atleast at a 1 gallon per hour burn rate the Prius will slowdown to less than 20 mph as it climbs uphill to Sunwood Lane.
  5. walter Lee

    walter Lee Hypermiling Padawan

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    Don't get me wrong I am not complaining - this particular
    section of road that I've describe is part of one of my
    best fuel efficiency routes (Olney to Germantown, MD)
    where I've been able to achieve about 75 mpg from a
    cold start. It's because this is part of one of my better
    fuel efficient routes that I am interested in optimizing it
    and analyzing it in more detail.

    Your Method 2 sounds like Gerdes' NICE technique.
    I am definitely will get more scangauge readings for this
    section of road.

    I am also thinking maybe I should switch off ECO mode and just run the Prius on Normal or Power mode so I can get better throttle response?

    I wonder if one of those data logging OBDII scanners might help?
  6. mikewithaprius

    mikewithaprius New Member

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    I didn't think you were complaining, just abnormally passionate about your mpgs, kinda like me :)

    I looked at the street view of the road on Google maps - that road looks great for hypermiling. What I'm suggesting is different than a NICE-on, which is just neutral with the engine on. I'm saying that since you have to run the engine anyway, I would just barely keep speed up the hill. It's hard to tell on Google maps, but I have a feeling it's the sort of gradual grade where you can get around 40 mpg while going 20 mph-ish by keeping the foot verrry lightly on the pedal, or 50 mpg at 30 mph.

    This is basically a low-speed super highway mode, since if you watch IGN and TPS when doing it, you'll find it around 14 and 18, respectively, or 13 and 19 - somewhere around there.

    Another way to think of it is the bare minimum pedal needed to keep the engine on - if you let up the slightest bit it would slip into EV...that's the engine-on area I'm thinking of.

    If the hill's a little steeper, just push a little more :)

    Personally I don't find it too useful to watch Scangauge when I'm doing this sort of thing. It's more just maintaining speed with minimal energy, which is all by feel, and maybe a little speedometer watchin'.
  7. fuzzy1

    fuzzy1 Senior Member

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    I am a non-civil engineer.

    Is this (from a Garmin topo) a reasonable representation of the section?
    [​IMG]

    The steepest slopes here, at Annamarie CT and climbing out of Rock Creek, display as just under 4 degrees.

    Toporoute.com shows a generally similar profile, but with more noise. It shows a steeper descent into Rock Creek (45 foot drop at 6 degrees), and a shallower climb out. It also varies between successive mapping attempts. But these computerized topos don't have real elevations for every point on the maps. Rather, they are just estimating elevations from some set of nearby datapoints, and I don't yet have a feel for how accurate they may or may not be along a requested track.

    Personally, I vote with Mike -- ignore the ScanGauge on this kind of road, keep eyes on the road, and go by feel.
  8. Rstaton

    Rstaton New Member

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    Maybe I need some re-educating. My understanding about maximizing MPG is that you want to use the engine at its peak efficiency when it's running. The method I read before is to aim for 1800RPM on the ICE. I had not heard of measuring GPH. Is that a better gauge of efficiency?
  9. JamesBurke

    JamesBurke Active Member

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    I grew up in Burtonsville. I know the roads your talking about. Your drive is so short your barely out of warmup, especially in winter. Since your ICE is running already your pulse and glides are already maxed also. I try to stay within 5 or 6 mph when P&Ging on little hills and valleys . Scanguage has a LOD display that can be useful on short uphills. By trial and error you pick a value that will get you up the hill at a suitable decreasing speed and try to keep it there. It will be different for each grade. Search here or at Cleanmpg for "Driving with load". For the distance your going you are doing quite well.
  10. mikewithaprius

    mikewithaprius New Member

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    My personal feel, especially from the last few days of mixing different types of acceleration into my driving with way better results, is that that RPM area is good for initial acceleration, or anytime you need speed. If you don't, a light acceleration is nice for couple reasons:

    1. It charges the battery more. If you only accelerate at 1800 RPM for pulse and glide, the battery will barely get charged since the engine's on for a short period of time, and more energy is going to the wheels. Each glide then progressively lowers your SOC. When you accelerate lightly the Prius is liable to throw a lot more amps into the battery.

    2. Overall mileage is still about mileage over a distance (well, duh, I guess, let me explain better haha). If you pulse at 25 mpg up a hill because the engine is working efficiently, it sounds good, but in reality if no more speed is needed, and you're going to glide when you reach the top of the hill anyway, and you can get 40 mpg over the same distance, that's definitely preferable. Again, what I mentioned in number one above also happens during this time. Better mileage and better state of charge.

    I've never really watched GPH either, can't comment on that.
  11. walter Lee

    walter Lee Hypermiling Padawan

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    Yeah the topo elevation description is pretty much on the spot.
    The road bottoms out at the tributary stream/creek.

    You have some really nice toys there. :)
  12. walter Lee

    walter Lee Hypermiling Padawan

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    GPH = gallons of gasoline burned by the engine per hour, its an XGAUGE on
    the aftermarket OBDII scanner called ScangaugeII. I found that it
    is a better overall indicator of fuel usage than looking at the
    RPM gauge.

    What I've learn is that the Prius is always running at peak efficiency
    but that driving conditions is a strong factor on the Prius fuel efficiency.
    For example, if the outside driving temperature drops from 70 F to
    below 32 F - the fuel efficiency of my Prius will dropped
    from 64 mpg to 52 mpg.

    Probably to no surprise to anyone, but
    the Prius is more fuel efficient if power is
    applied while going on a downhill grade.
    The Prius get a higher velocity and a faster
    acceleration for the same amount of
    energy when the power is applied while going
    downhill (regardless of whether the power
    being applied is gasoline or electricity).
    If I can synchronize most of the power
    applications with a downhill grade, it
    will have a signficant positive impact on
    the Prius' overall energy efficiency. However,
    with downhill grades come uphill grades. To
    optimize fuel efficiency one needs to
    have driving tactics/skill that will
    minimizing fuel usage for the uphill grades
    -- especially from a dead stop. High
    accelerations and top speeds during
    an uphill grade can kill fuel efficiency.
    hence the question...

    In addition, Gliding is turning out to be trickier
    than I first anticipated because of the
    electrical drain on the traction battery.
    When gliding for an extended time
    period the electric motors can eat up
    too much power and the Traction battery
    state of charge can drop lower than 45%
    which THEN triggers the ICE to automatically
    run aggressively for several minutes to
    recharge the batteries which ends up
    being a -3mpg to -5 mpg penalty which
    takes the driver double time to undo!
    So to get the best fuel efficiency
    on a Prius, the driver should work to keep the
    Traction Battery SoC at above 50%
    which translates to about 4 bars on
    the Hybrid system Indicator display.
  13. fuzzy1

    fuzzy1 Senior Member

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    I must disagree here. On slopes, instant MPG is meaningless without a proper accounting of changing gravitational energy. This is not included on any of the common display tools, and is well beyond the on-the-fly mental computation of most of us.

    On rolling hills, MPG needs to optimized only over the complete up-and-down cycle, not over the ups and downs separately. My best hill results occur with burning fuel at an efficient ICE setting on the climb, then gliding down a shallow descent with no braking, ICE shut down, and no or very little electric propulsion. Not all hills are in the right range of slopes to pull this off well.



    This sounds more like EV or Warp Stealth modes. A true glide puts no power into the electric motor. The reality is that we often add a little electric thrust to extend a glide, tuning it to better fit the situation. But do be aware that if the battery SOC drops sharply, then you aren't really gliding.
  14. mikewithaprius

    mikewithaprius New Member

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    I've taken the liberty of making a paragraph up there haha...not sure why your formatting comes out so weird!

    Back on topic, looks like Fuzzy and I will go back and forth agreeing with each other :) You're not gliding, you're using "stealth" mode, i.e. electric propulsion. This is actually something to be avoided for just the reason you say. 45% sounds "dangerously" low (I use the the word loosely, but basically I would never run the battery so far down...).

    Judicious, sparing use of EV is great, but you're using it all the time without realizing. If you back off ever so slightly on the pedal for your glides, and have the HSI bar barely show at all, if it even does (not sure if it can be completely absent from view since I'm a Gen II driver, but if it can be, that would be ideal), that's what you're looking for - the glide. The more you bring up the HSI bar toward the center, the more in stealth mode you are. When you get the hang of keeping it far left for a good glide I think you'll be pleasantly surprised at the cool little bump up in mpgs you'll get.
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