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hypermiling by coasting in neutral

Discussion in 'Gen 2 Prius Fuel Economy' started by ChrisPR77, Jan 9, 2017.

  1. Kevin_Denver

    Kevin_Denver Active Member

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    This isn't true. When the battery reaches full charge (~80% - all bars green), the regenerative braking disengages, and the car will use the electric motors to spin the gas engine (with no fuel injected, only pumping air) to use up the excess energy. On my Scanguage, it's obvious because I can see the engine RPM change from 960 to about 3000 coming down hills on I-70 in Colorado. The car won't let you exceed ~80% (actual is something like 83%) state of charge on the battery.

    When the battery is full and you're on a steep downhill, it's best to use the B mode to engage engine braking to keep from overheating the brakes. Better yet is to engage B at the top of very long steep downhills, to more gradually charge the batteries and reduce brake use.
     
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  2. valde3

    valde3 Senior Member

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    I did realize that those are just US laws. It’s not illegal here. And I still don’t get why it would be illegal or bad idea anywhere. It’s not beneficial in a Prius but still you do safe fuel by coasting in neutral with most of cars.

    Actually here in driving school they used to teach you to coast downhills in neutral to safe fuel when cars still had carbonators. In carbureted car there’s no fuel cut at engine breaking so you do safe more fuel than you would if you do the same thing with modern car.
     
  3. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    US drivers are not nearly as talented.

    Laws like that are (usually) written in blood, so obviously there was more than one time where somebody became an organ donor because somebody (or somebody else) forgot that when you put a vehicle in Neutral you're no longer able to use compression braking.
    Over time, friction brakes heat up, and lose effectiveness.

    Evidently, either this happened over and over and over again here in the US or lawmakers just sat around making up daffy laws because it's a lot more fun than golfing, chasing interns and accepting graft money.
     
  4. valde3

    valde3 Senior Member

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    Maybe the long and expensive driving school that we have here with multiple phases really helps. Normally people here just complain how expensive it is.

    Second phase (now it’s actually third phase) that you have to complete within two years of getting your license has skid control on a track with own car and economical driving (with their car).
     
    #24 valde3, Jan 9, 2017
    Last edited: Jan 9, 2017
  5. Velo781

    Velo781 Junior Member

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    You lose engine braking when in neutral, even with an automatic. I once was in my auto 92 Corolla and wanted to see how fast it would coast up to down a long hill. Stopping from 80mph on a down grade with no engine braking is bad for the brakes and unsafe.
    I am eager to get my Prius so I can experience no drag coasting while still having full control.
     
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  6. Sam Spade

    Sam Spade Senior Member

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    I think that if you practice more than:
    Slow down
    Anticipate what is coming so you can adjust your speed and lane choice early
    Then it really amounts to distracted driving.
     
  7. Sam Spade

    Sam Spade Senior Member

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    Total BS.
    The car will save itself.
    The driver "needs" to do nothing.
     
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  8. Mendel Leisk

    Mendel Leisk Senior Member

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    Maybe the smouldering brakes will ignite the overcharged, exploding battery? :coffee: (Purely coffee talk)
     
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  9. bisco

    bisco cookie crumbler

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    at 5 o'clock?
     
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  10. AKCoffee

    AKCoffee Junior Member

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    I'm in favor of neutral glides to avoid energy conversion loses. In my PiP downhills some times < 62 mph or in cases where I want to slowly bleed off speed without coming to a full stop: rush hour, stale red lights, roundabouts. I'm relative flat lander in Minnesota so the glides are always less than a mile and not done on low SOC. At least for me, holding a soft glide ... engine off no regen no assist longer than a tenth is difficult. As cars use topographical, traffic and other senor data to maximize FE they will increasing auto n-glide when it's the optimal mode.
     
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  11. fuzzy1

    fuzzy1 Senior Member

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    It is illegal because it has killed many many people, though mostly back in your grandparents' era.

    Back then, brakes (nearly always drum, not disk) were weaker and much more susceptible to fading when hot, allowing the car to begin rolling too fast. Then the lack of any synchronizing mechanism often made it difficult to impossible to re-engage the transmission, resulting in a run-away vehicle and a fatal crash.

    Modern vehicles, with power disc brakes and automatic or synchronized-manual transmissions, are far less susceptible to this catastrophe. So for modern passenger cars, these laws are a bit of an anachronism, a holdover from previous generations.

    But it can still happen in passenger cars, and definitely does still happen in heavy trucks. That is why the long steep mountain grades have runaway truck escape ramps.
     
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  12. ChrisPR77

    ChrisPR77 Junior Member

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    I tried out the feathering the peddle today to trick it into coast without regenerative braking. You can see the screen go blank if you do it right. It works a few had posted on other threads about wishing they could shift to N to avoid this kind of awkward feeling produced from the maneuver. However, since being in N would be against the law I think I will stick to feathering the peddle it gives you more control over charging anyway.

    As far as the towing. I was thinking it wouldn't be different because if you did any kind of towing with all wheels on the ground in N I would assume. This would be very similar to N coast. Maybe the car would perform differently without a driver and the car on? I don't know enough about the car yet to say why.
     
  13. ChrisPR77

    ChrisPR77 Junior Member

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    Coasting the Civic days are over. I did have success today with the feather peddle technique to trick it out of reg braking and I am satisfied with this as an alternative. Thanks.
     
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  14. ChrisPR77

    ChrisPR77 Junior Member

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    You would be surprised with the engine and transmission disengaged the car has way less resistance. You basically turn your car into a bobsled that could go infinitely faster and faster. I am almost 40 and just learned about it. No doubt you could get way over 100mph with no gas.
     
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  15. ChrisPR77

    ChrisPR77 Junior Member

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    tried it and it works happy with the alternative. thanks
     
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  16. ChrisPR77

    ChrisPR77 Junior Member

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    I am new to this but I agree. Hypermiling does consist of over inflating tires for instance. Hypermiling is anything that gets you better mpg beyond or in conjunction with how the car is to be driven.
     
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  17. ChrisPR77

    ChrisPR77 Junior Member

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    Thanks. I was wondering how to look up the law for myself and I couldn't figure it out yesterday morning. Damn youtube trying to get me in trouble. =)
     
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  18. ChrisPR77

    ChrisPR77 Junior Member

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    this is kind of a weird contention about if towing and N coasting are the same. in the manual you aren't even supposed to tow with a chain all 4 wheels down. That limits do-it-yourselfers. So why can't you put it into neutral with the car off like a normal car? Also again why does the prius even allow you to shift into N at speed?
     
  19. ChrisPR77

    ChrisPR77 Junior Member

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    this is my sentiment exactly. i am not sure if it can damage the engine. Some blogs write how it could damage EM1 by over rev'ing it. I am not knowledgeable enough to say. Since it is illegal we may never be told by Prius. probably I am going to stick to peddle feathering myself. it works and doesn't brake the law. I understand the maneuver is less than desirable for me to. As I am sitting here writing I am thinking of holding my foot that way and it is annoying but I will have to get used to it. Wish they had designed it in there a little more comfortably.
     
  20. ChrisPR77

    ChrisPR77 Junior Member

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    Interesting topic. Most of us probably don't know its illegal because the gov doesn't want us to know how to do it. Damn youtube for getting us into trouble. =)