'08 - no-arrow glide at 50mph+ - normal or wonky MFD?

Discussion in 'Gen 2 Prius Main Forum' started by brightlights, Sep 6, 2016.

  1. brightlights

    brightlights New Member

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    New-to-me 2008 with 91k miles. I've had it for a week and a half and have diligently read everything my search hit; I apologize if I've missed something.

    I was under the impression that the Prius should only hold a sustained no-arrow glide state at 42mph or below. At higher speeds it may pass through a glide state for a few seconds on its way to throwing arrows around somewhere else but it won't stay there. However, I've been able to replicate a 15sec+ stretch of glide at 52-58mph on a couple of stretches of my commute, most often but not always downhill.

    I've also noticed a pretty substantial difference between average MPG on my last tank of gas per the MFD and average MPG on this one in the same conditions, although the second-gen gas gauge silliness is making that a little hard to calibrate and I know that a discrepancy between actual vs. displayed MPG is normal. 55mpg on a primarily highway commute seems a little too good to be true for someone just learning to drive this machine, although I won't complain if it turns out that all my reading about how to operate it efficiently paid off quickly.

    Since I'm a newbie at this whole hybrid thing, I'd appreciate thoughts on whether the sustained higher-speed glide sounds like an expected result under certain conditions, or whether I should be skeptical about the display.

    Thanks in advance!
     
  2. Kevin_Denver

    Kevin_Denver Active Member

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    No-arrow glides are possible at over 41mph, just require the right conditions and a very precise right foot. The behavior I've observed is no arrow glides are possible when the battery is in a normal to high range (around 5 to 7 bars). If the battery is 4 bars or lower and speed greater than 40 mph, glides aren't possible as it will instead drive the engine at a low rpm and charge the battery when applying gas past the blue charging arrow. If the battery is at 8 bars it tends to drive power to spin the engine to let off excess charge. This is what I've observed, and not definite. No arrow glides also seem to be easier in S4 than in S3 (See warmup stages).

    Below 40 mph in EV mode the range on the gas pedal where no bars are shown is much wider than at higher speeds.

    It should be understood that engine turning glides (so those above 41mph) are generally an inefficient state of the engine to use. If you have a stretch of road you take and hold engine rpm at 1400 for the entire stretch versus doing 2200 rpm pulses and then engine on glides, you'll find that better FE is achieved by holding the engine rpm steady at 1400. In hypermiler terms, on the Prius above 41mph, in general it's better to drive with load than to pulse and glide. Below 41mph, the opposite is true.

    Also the displayed mpg is 4-7% greater than actual. This is well observed on gen 2s. I have my Scanguage calibrated from many tanks of gas and the Prius' displayed mpg is about 5% greater than on my Scanguage.

    This is super fun to play with to understand the HSD: Toyota Prius - Power Split Device

    This is good read too, to understand how to use the Prius' engine most efficiently: Prius throttle control

    Consider getting a Scanguage if you want to be able to dive deeper while you drive (e.g. monitor your engine rpm, trip mpg, water temp, etc.). Using the Scanguage and holding my engine rpm between 1400 to 2200 nets me a lot of 60+ mpg trips.
     
    #2 Kevin_Denver, Sep 6, 2016
    Last edited: Sep 6, 2016
  3. dolj

    dolj Senior Member

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    Hi and welcome to PriusChat.

    This is correct, but needs to be qualified by "(or less) on a flat road–for the most part.
    This will happen when the right circumstances, such as battery charge, battery temperature, slope of the road (down-hill), etc, all line up. I have noticed this too, but it usually does not last for long and also it usually happen of its own accord and not really something I can easily replicate on a regular basis. I will note, that it is easiest to make happen (if it is going to happen at all) on a longish slightly down-hill gradient.
    Notwithstanding the foibles of the (North American) Gen II fuel tank bladder, I have notice that I get more optimistic readings from the onboard MFD consumption screen when I have done a lot of active gliding on a tank.

    Your have made some good observations, I hope you continue to increase your knowledge and more importantly your enjoyment of driving this fun vehicle.

    hope this helps.
     
  4. brightlights

    brightlights New Member

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    Thank you both! I'm trying to learn what's normal to observe on the display. The resources on this forum and elsewhere have been very valuable. I know that a ScanGauge will be the best way to truly calibrate my driving for best efficiency but I'm worried that it will be overly distracting to monitor that and the display on top of the road, so I want to focus on learning the car better before I invest in one.

    Thanks too for the heads up on the MFD's "optimism." I'm experiencing a 15% increase in MPG reported by the MFD versus my calculated average on my last tank, but it's possible that I've learned how to drive it better, so we will see how the display compares to mathematical reality when I fill up next!

    I'm really enjoying this little car. I'm coming off of an 01 Civic, which had a 35MPG year round average that's certainly nothing to sneeze at for a typical vehicle, but it only took me about 2 hours of driving the Prius to find 40MPG terribly unsatisfying. :)
     
  5. 09Prius2

    09Prius2 Member

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    Theres alot of variables to consider besides speed. Ascent/descent as you mentioned, don't forget wind speed, as well as throttle control among other things. I drove through the mountains of west virginia and was astounded by the vehicles capability to control speed and manage energy. Apparently it is smarter than we are.
     
  6. dolj

    dolj Senior Member

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    Who'd a thunk! ;)
     
  7. 09Prius2

    09Prius2 Member

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    All we need now is a Knight Rider version of the prius, perhaps the Prius Outlaw. It could communicate to us through our smart watches and phones while the vehicle is parked, and help us with:

    Casino Gaming
    What to say to women
    Rescue us from those random pesky shootouts

    The only next logical step would be an Airwolf Prius. Noone would ever call a prius slow again.

    Perhaps if I poured this can of Four Loko into the prius gas tank instead of my mouth, these goals would be accomplished. Maybe not. Might be time for bed.
     
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