Took me 17,000 miles to work this out....

Discussion in 'Gen 4 Prius Main Forum' started by benlovesgoddess, Feb 2, 2017.

  1. benlovesgoddess

    benlovesgoddess Active Member

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    I often feel like some chump who accidentally bought a Prius, rather than an elite member of the club...
    I'm new to Hybrids after a lifetime of diesels.
    I tried reading various hypermiling essays specific to the Prius, it pointed me in the direction of the stealth pulse and glide technique, etc...
    Ever since I got the car, I used to wish there was a way to force it to use the petrol engine at times when driving at 50-60 mph in traffic it had switched itself to electric due to being within the eco part of the rev counter bar thing.
    Driving diesels, to slow down you take your foot off the accelerator, applying it again at the desired speed, as no throttle pressure means no fuel used.
    In the Prius this meant I would release the accelerator while using petrol, and apply it again in electric mode.
    Quite by accident today, my revs went from above the eco line to below the eco line, but with my foot still on the gas -and the petrol motor stayed on....
    So there's the way to force it to stay in petrol while the petrol motor is most efficient, rather than draining and recharging the battery in a clumsy and inefficient manner while on the highway.
    Don't take your foot off the pedal.
    I take it almost everyone here already knows this, but in case anyone doesn't, I thought I better mention this...it's not information I picked up in the handbook, or forums or hybrid driving tips.
    When I got the car, I drove it really steady, getting high 60s-70 mpg (imperial).
    Over the last few months I have just stuck her in Power mode and put my foot down - low to mid 50s my likely MPGs.
    This morning, just on the last half of my commute (I twigged about 13 miles in), I managed to get an indicated 67 mpg on the screen, rather than 55 by the time I got to work.
     
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  2. RCO

    RCO Senior Member

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    Just remember Ben, the engine will come on if the ECU needs to heat the coolant system or supply optimum power for any of the systems. There is a logic in there, it's not always easy to understand it though.
     
  3. alanclarkeau

    alanclarkeau Senior Member

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    I wouldn't count on it always happening that way - if you start going down a gentle incline after driving on the level with ICE running, but with a little accelerator to hold your speed, generally the ICE will turn off and use just battery, unless the battery hasn't got sufficient charge or it needs to heat the car. Or any of many other reasons why it decides to "do it's thing. Sometimes I've encountered what you said - and I can't fathom why.

    The same as tonight, full battery, hot night so no heater, a/c, been driving about 25km, last 2 km at 70km/hr. Stop at traffic light, pressed EV because there was another light 100metres up the road, and got "EV UNAVAILABLE" with no reason given.

    It's a mystery sometimes.
     
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  4. pakitt

    pakitt Senior Member

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    I can only say one thing: just drive it.
    Reduce sudden and strong accelerations and braking. Predict traffic. Drive "smooth" whenever possible, reasonable and safe. Keep up with traffic. You will have the best fuel consumption.
    This is my second Prius in since 2009, whenever I tried to do anything else and not drive smooth as a result because too worried of how I would accelerate, etc, I had lower MPGs. I drive it smoothly, I get the highest MPGs. I also think that P&G is not necessary anymore with Gen4 to get great MPGs. What gets great MPG is smooth driving, well inflated tires, and lower speed if possible/reasonable.
    Also consider that temperature affects the MPGs, and if the heater is on, the engine will come on to keep warm, or it will stay off because more efficient in that particular situation. Let the engine decide. Toyota has almost 20 years experience in this. Let the computer decide what to do with its hardware.
    Sit back and enjoy the drive, don't think about it.

    PS: the "score" is weird - when it is low, sometimes I get great MPG - when high, I get the opposite in the same or similar conditions - I simply don't look at it anymore.... :D
     
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  5. Prodigyplace

    Prodigyplace Senior Member

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    The Prius tends to keep the petrol motor running at its most efficient, draining & recharging the battery is generally more efficient, especially when regenerative braking is used on downhill portions of the trip.
     
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  6. kithmo

    kithmo Couch Potato

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    It has the mind of a woman :D with a headache.
    I'm waiting for mine to give me the message, "Score: 1, surrender your driving licence to the nearest police station"
     
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  7. Tideland Prius

    Tideland Prius Moderator of the North
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    The Gen 4 definitely has new ways to discover in terms of fuel efficient driving.

    In the Gen 3 with the lower 70km/h engine off threshold (vs. 110km/h on the Gen 4), there is a heretical mode or super highway mode in the Gen 3 where (assuming enough battery charge and a warm engine), you hold the accelerator right such that the Hybrid Eco area is full (so the first half of the Hybrid System Indicator). At 70km/h, if MG1 is disengaged, you'll be holding speed and getting 2.5L/100km-3.0L/100km (94-113 Imperial MPG). If MG1 is engaged, it'll drop to 4.5L/100km, maybe 5L/100km (63-56 Imperial MPG).

    Perhaps that's what you saw in your Gen 4 - the engine went into that mode where it's powering the wheels directly and MG1 was disengaged (so it wasn't charging the battery).
     
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  8. Gen 2 Tom

    Gen 2 Tom Active Member

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    Just drive the car. if your light on the accel your mileage will be fine. I never reset the mpg display an it's at 61.2
     
  9. RCO

    RCO Senior Member

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    Thanks for that. I believe I have seen that happening once or twice now and thought it was a glitch/lag in the display diagram.
     
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  10. benlovesgoddess

    benlovesgoddess Active Member

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    Occasionally just a red arrow to the wheels? Only seen that a few times.
    In cruise control the car does it itself, as the rev counter breaks below the eco line, the petrol engine still runs but the indicated live mpg can break 100-120 mpg (but still shows charging).
    My style of completely removing my foot while above eco bar and reapplying below always meant it would switch from petrol to electric.
    Not removing my foot at the transition means it remains in petrol mode, but substantially more economically.
    I have gone from only caring about economy to enjoying the power and drive of the car, but would still like to get the highest possible mpg (whilst booting it!)
     
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  11. Tideland Prius

    Tideland Prius Moderator of the North
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    I couldn't find one with the Energy Monitor but here's one that shows the HSI and iFE.

    The HSI (sorry for the refresh line across the screen) bar is just to the right of the Eco light (or equivalent in the Gen 4). At this instant, the iFE is showing 3.5L/100km (each bar is 0.5L/100km) even though I was doing 90km/h (56mph). I was loosing speed of course (not enough power to maintain speed so it's like a high speed pulse and glide). As you can see, the average at that time was 3.2L/100km (88 imp. mpg). That day ended up close to 4.1L/100km (68 imp. mpg).

    This works at lower speeds (70-80km/h) where the engine output is enough to maintain speed or at least slow down the drop in speed, allowing you to stay in Super Highway Mode for longer, maximising fuel economy.

    (Note the photo was from the passenger side.... cause it looks like the driver's side from your UK perspective)

    IMG_4269.JPG
     
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  12. Kramah313

    Kramah313 Active Member

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    I have found in my gen 3 that this technique (which I also use at times) is easier in PWR mode. The car seems to be reluctant to turn the engine off in PWR mode if your foot is still on the gas unless the battery state of charge is very high. I drive almost exclusively in PWR mode and you mentioned you have started doing that as well - my theory is that the car wants to remain as responsive as possible in power mode, thus keeping the engine on to avoid the small delay of tuning it back on if it thinks you might want to start it again soon anyways.

    It might be possible to get the same behavior in the other modes, but you'd probably have to press the pedal further down.

    I usually use this technique when I am traveling around the speed where the engine can't shut off and know I have a long shorter stretch coming to conserve battery power.
     
  13. Prodigyplace

    Prodigyplace Senior Member

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    That does not look like Gen 4. At least. Or mine. The OP has a Gen 4. Our HSI looks different.
     
  14. Tideland Prius

    Tideland Prius Moderator of the North
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    I know, I know. That's MY car, a Gen 3 :) I was using my car as an example. I don't get to drive the Gen 4 often :(
     
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  15. Prodigyplace

    Prodigyplace Senior Member

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    I thought perhaps you lost your way and thought you were in a Gen 3 thread.
    Perhaps if you talk nicely, she will let you drive the Gen 4 more?
     
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