Short trips? Here's a trick!

Discussion in 'Gen 2 Prius Fuel Economy' started by nooaah, Sep 19, 2008.

  1. nooaah

    nooaah New Member

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    I know, but I get the same issue in warm weather when driving around the city. The problem with Philadelphia is you have to stop at every block, and every block is short. They basically give you no shot to drive for longer than 30 seconds or so without stopping. The trick is to take public transportation when you're downtown and maybe walk a little. :p
     
  2. stellaf

    stellaf New Member

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    Hello everyone.
     
  3. stellaf

    stellaf New Member

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    Wanna be your friend.
     
  4. stellaf

    stellaf New Member

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    Nice article.
     
  5. stellaf

    stellaf New Member

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    Great place for outing.
     
  6. stellaf

    stellaf New Member

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    Please suggest me a good travel agent.
     
  7. GreenJuice

    GreenJuice Member

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    Thanks Donee,
    Can you confirm that the behaviour is really the same? The picture in my previous post#31 shows me in S2 (below 70 C) and gliding with engine-off (RPM = 0) while travelling at 24 mph.

    The most 'FE challenging' urban commute I have to do in London is only 4 miles long, from a cold start, 14 stop lights & in current temperatures just above freezing. Most of this is done below 30 mph and if can minimise engine use by being lucky with my glides and stop lights, engine temp often doesn't even make it to 60 C before the end of the journey.

    Before pushing up tyre pressures, grill blocking, engine block heating & taking other advice from this website, my mpg was in the 30s; now its regularly in the low 60s for this journey, thanks to priuschat.com!
     
  8. timberwolf

    timberwolf New Member

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    GreenJuice did you really have an EBH installed in your Prius for use in London UK?
     
  9. GreenJuice

    GreenJuice Member

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    Not the specific fitted product that you see on sale on this website. I inherited a 'garage-use' electric radiator which I put on a timer and lay it underneath the engine block. I have my front grills completely blocked. Start up temperatures are about 30 C when its 0 - 5 C outside, so I regularly hit S2 (over 40 C) in less than a minute after setting off.

    I'm learning each day - if you are aware of other alternatives that work let me know!
     
  10. timberwolf

    timberwolf New Member

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    Ah. No, I don't know of any alternatives.

    I thought about it for my past non-Prius vehicles and I've always wondered at what temperature you need them. In Canada, my Dad used to have an EBH for his car when he lived in Alberta, but not since he moved back to Ontario - but I am sure the reason for the EBH wasn't fuel economy but just to prevent the engine freezing solid.
     
  11. Rokeby

    Rokeby Member

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    I've been playing around with the EV switch that I installed a month ago. I'm
    slowly figuring how to use it effectively on the very different ends of my
    commute; using it to suppress ICE-ON, and getting access to ICE-OFF (no
    arrows) glide while the ICE hasn't warmed up.

    I find this to be very challenging, even confusing. Sometimes the HSD reacts
    as I expect, sometimes not. Most discussions of the HSD operating states at
    least mention ICE and exhaust catalyst temps.

    I'm beginning to wonder about the temp of the HV battery. Could it too be a
    determinant of when ICE-Off glides are accessible?

    Electrically speaking what benefits would there be to having the HV battery
    warm at start-up?

    What would the desired temp range be?

    This raises the additional question of if you are using an electric block
    heater, EBH, would it be helpful to also use an Electric HV battery Heater,
    "EHH?" (I made that up) -- something like a small heating blanket.

    I have a ScanGauge, but haven't yet programmed the HV battery temp
    XGauges, so I don't have a good feel for what lower HV battery temp might
    be the threshold. As I recall, the XGauge readout is in degC.
     
  12. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    i believe there is a safety feature built into the traction battery to prevent EV operation if internal batt temps is too high to handle high rates of discharge
     
  13. Rokeby

    Rokeby Member

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    I would expect a high temp cut out for the HV battery. In fact once last sumer,
    when I parked the car in an uncovered lot, I experienced not being able to get
    HV battery-only propulsion. Posters pointed out that it was likely that the HV
    battery had been heated to the same ~100 degF temp as the passenger
    compartment.

    What I'm now wondering about is low temp HV battery use limits in S2, S3,
    and S4. In cold temps using the EV switch to get "unnatural," long no arrow
    glides, the ICE temps can fall below 100 degF in stop and go traffic, especially
    on a slightly down sloping roadway.

    It could be a tricky thing to identify as, IIRC, on start-up, S1, the HSD draws
    heavily on the HV battery as the ICE first fires up.
     
  14. Helio

    Helio Member

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    Here's a question: is it possible to not even achieve S4 during highway driving in cold (below 25 F/ -4 C)? I haven't done the grill blocking yet and twice while driving at speeds of 65MPH my MPG were what I consider horrible (<39MPG).
     
  15. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    actually, large temp fluctuations are normal especially if running heat at the same time. in winter, i can take off, get water up to the 175 range. and stop at a light with heat running, by the time i take off again within 90 seconds or so, i can be as low as 140.

    and yes, if cold enough, its very possible. the problem is as stated above, even short periods where the engine shuts off can cause you drop back down to S2. this does kill the mileage
     
  16. Rokeby

    Rokeby Member

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    DaveinOlyWA,

    As you have noted, I have found use of cabin heat makes a big difference in
    low temp, low speed, stop and go driving. In my urban driving situation it
    can be as much as 5 MPG over a 7 mi. commute leg. When I'm alone I can
    get away with no heat, but not with a passenger.

    At the risk of appearing lazy, I admit to hoping that someone else has
    already explored the matter of low temp HV battery usage limits and will
    share the info.

    Using the EV switch in low temp driving has proven to be anything but
    simple and is highly dependent on route selection. It has involved
    intentionally letting, even forcing the ICE to run to keep coolant temps up on
    the theory that S4 is maintained. The ICE running also keeps the SOC up
    which gives extended no arrows glides and yellow arrow propulsion which
    drops the coolant temp downward. It's a real juggling act, with three "balls
    in the air."

    Trying to also monitor HV battery temps and use yellow arrows propulsion
    to keep it above some low threshold would add a "forth ball," and is
    probably beyond my capabilities.

    That said, if there is a low HV battery temp threshold, I would at least try to
    factor it in.
     
  17. diamondlarry

    diamondlarry EPA MPG #'s killer

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    I have found that when the HV temp drops to ~25-30F that EV use is not allowed. When I try to use the EV switch to kill the ICE, I get the friendly 3-beep denial. This also means that if you even breathe on the gas pedal when taking off from a stop that the ICE will run. I wonder if Hobbit knows of a way to hack the HV temp sensor so that the ICE can be shut off?
     
  18. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    you can force EV mode on startup at any temp, but use like this can easily damage batteries if abused.

    to be honest with ya, when i first got my EV switch 4 years ago, i played with it a lot in all kinds of conditions and found its best use only when moving the car a few blocks at a time.

    if driving any distance, i dont really recommend using it at all. i know it seems like the thing to do is to force EV for maybe the last mile of your commute, but i tried that extensively and saw no real benefits to it.

    i used to live on the side of a hill so it was a pretty steep drop for the first 8 blocks so i used to EV it to home, get to 3-4 bars thinking i would get them back when coasting back down the hill. it never really provided any change in my overall mileage.
     
  19. diamondlarry

    diamondlarry EPA MPG #'s killer

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    You bring up a good point about using EV mode and I agree, EV should be used sparingly. This is why the vast majority of the times I use the EV switch is to shut the ICE off when I haven't gotten a chance to come to a stop long enough to do the S4 idle check.
     
  20. Rokeby

    Rokeby Member

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    Dave,

    I have to laugh, I'm still in the playing-with-the-new-toy stage, and I will
    admit that maybe I expect too much.

    Dave and Larry,

    First thing on cold mornings, I have had EV mode refused at MFD indicated
    temps of 28, 30, and 32 degF. I have gotten EV mode at 36 deg.

    My question has to with HV battery temps later on.

    Yesterday I had an incident that I just can't integrate into what I thought I
    "know." The car sat all day in 40 falling to 36 deg temps. I did get EV on
    start up. Shortly into the drive, after EV to get out of the garage and through
    a slow speed section of stop sign and lights, I forced ICE-ON to keep SOC at
    4 bars. After a short while, coolant temps were up to 91 deg. At the next
    light, the ICE went off unexpectedly. In the past I needed coolant temps of
    >110 degF to see auto-ICE-OFF on stopping. I don't know at what temp the
    catalytic converter is "warmed up," but I have to believe that it wasn't.

    Strangely, this got me to thinking about HV battery temps... non-linear
    thinking, ain't it great?
     
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