1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Gas Pip Lines

Discussion in 'Gen 2 Prius Fuel Economy' started by Tassee, Aug 28, 2008.

  1. Tassee

    Tassee New Member

    Joined:
    Aug 16, 2008
    27
    0
    0
    Location:
    Pittsburgh, PA
    Vehicle:
    2008 Prius
    thank you for being so nice Tom :) I went thru my manual today but it really just shows you what's in the car and how to operate stuff like the radio and the bluetooth, but really nothing about technical stuff, like the battery turning purple. etc. Marcia
     
  2. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,075
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    You are welcome.

    The Prius approach to battery management is conceptually fairly simple. It tries to optimize the use of the engine by running the engine at efficient loads and speeds. To do this, it uses the battery as a booster when needed, and to store excess energy when available. For example, when creeping along in stop and go traffic, it doesn't make much sense to run the engine if battery power is available.

    On the other hand, if the Prius finds that it needs to run the engine in this situation, for example due to a low battery or needing heat for the cabin, then it might as well run the engine harder and get it up into a more efficient range. To do this, it runs the engine harder and uses the extra energy to charge the battery. This is one of the reasons that green battery bars are more common in the winter. The engine has to run often to keep the car warm, so while it is running it charges the battery.

    Under heavy acceleration, it's more efficient if the engine doesn't have to run wide open. Before the car will do this, it tries to draw power from the battery and boost the acceleration with the electric motor. If it needs more power, or has to do this too long, it gives up and cranks the engine wide open, making that horrible racing engine sound.

    Just think of the battery management as a balancing act. The controller wants to keep the battery in the blue bars, but will compromise as needed for better efficiency.

    Tom
     
  3. Tickwood

    Tickwood Active Member

    Joined:
    Jul 27, 2004
    334
    101
    0
    Location:
    San Diego
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    Amazing, on my car when I have gone 180-220 miles I am down to two or at most three pips.
     
  4. Tassee

    Tassee New Member

    Joined:
    Aug 16, 2008
    27
    0
    0
    Location:
    Pittsburgh, PA
    Vehicle:
    2008 Prius
    Okay, after reading again I started to read again but I'm still in the dark... My first pip disappeared after 77 miles, the second pip went after another 22 and the 3rd went after another 22. What the heck is going on? Also, I was getting 50 or 51 mpg now down to about 44. Nothing has changed, still going to work the same way, driving the same distance, using the same gas. Any help here? Marcia
     
  5. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,075
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    It's not that hard to understand. You are over-thinking it. The main thing to understand is that the fuel pips are non-linear, or to use non-mathematical language, they are uneven. Don't expect them to disappear at the same rate.

    Almost all automobile fuel gauges stay at the full line for a fairly long time, then fall more rapidly after that. The reason for this is that it's not very important to know that you have a full tank, but it is important to know when your tank is almost empty. Since the fuel gauges are relatively simple and inexpensive devices, the auto makers build the error into the full side of the gauge where it doesn't hurt as much. Also, of course, the miles per pip varies with your miles per gallon.

    As for you mileage variation, that's fairly common too. Some minor change has lowered your mileage. It could be colder weather, one or two short trips, a change in fuel formulation, or any of a dozen other things. Don't worry, it will come back up eventually. Make sure to keep an eye on your tire pressure, as this is one sure way to kill mileage.

    Tom
     
  6. Tassee

    Tassee New Member

    Joined:
    Aug 16, 2008
    27
    0
    0
    Location:
    Pittsburgh, PA
    Vehicle:
    2008 Prius
    Tom, should the tires be inflated to what Toyota says or overinflated slightly? Marcia
     
  7. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,075
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    That's a personal choice. Obviously the manufacturer's recommendation is the safe choice. That said, many drivers on this board use higher pressures. I run mine a few psi higher than the recommended setting, but I don't go up to the max like some. It's important to keep the front tire pressure two psi higher than the back. This helps compensate for the extra weight on the front end.

    If you want to experiment with higher pressure, try going up about four psi and see how it feels. If the ride becomes too noisy or harsh, drop back down.

    Tom
     
  8. NC_Prius

    NC_Prius Member

    Joined:
    Sep 4, 2008
    186
    5
    0
    Location:
    USA
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    I understand what Tom is saying, but still, I'm like Tassee -- her mileage really does seem low for the pips to disappear regardless. My first pip lasts until about 130-145ish and on the way home this evening only the 2nd one was gone and I was around 200 miles since fillup. Could there be something with the bladder that would cause such a discrepancy?
     
  9. Bob64

    Bob64 Sapphire of the Blue Sky

    Joined:
    Apr 9, 2007
    1,540
    93
    0
    Location:
    Virginia
    Vehicle:
    2007 Prius
    Model:
    N/A
    There is more gas at the top of the bladder then the bottom.
     
  10. Jack66

    Jack66 Kinda Jovial Member

    Joined:
    Jan 26, 2008
    766
    6
    0
    Location:
    Stafford, Virginia
    Vehicle:
    2008 Prius
    Tassee, you are asking a lot of good questions. The answers to many of them are in the homegrown Prius owner's manual : John's Stuff - Toyota Prius User-Guide

    and searches of the PC forums. Using the Google search in the search tab up top works well or you can do the same thing by googling a subject and adding priuschat.com to the search phrase. Adding the .com site tells Google you want to concentrate your search to PC or another website. :)
     
  11. NC_Prius

    NC_Prius Member

    Joined:
    Sep 4, 2008
    186
    5
    0
    Location:
    USA
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    Right, but she was speaking about the top -- the first pip would disappear after just 77 miles then the 2nd after another 22, and then was down to half-tank with low mileage. Regardless of how the guess-gauge works ... it seems like something is wrong for the gauge to go down that quickly (?).
     
  12. Bob64

    Bob64 Sapphire of the Blue Sky

    Joined:
    Apr 9, 2007
    1,540
    93
    0
    Location:
    Virginia
    Vehicle:
    2007 Prius
    Model:
    N/A
    Perhaps there wasn't as much gas in the tank that time?


    This is an artists illustration of the gauge.

    [​IMG]
     
  13. NC_Prius

    NC_Prius Member

    Joined:
    Sep 4, 2008
    186
    5
    0
    Location:
    USA
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A

    Ah, thanks for the illustration. I guess that's it then. Maybe she got the shut off early or something. Sounds like she had it happen several times like that too.
     
  14. Tassee

    Tassee New Member

    Joined:
    Aug 16, 2008
    27
    0
    0
    Location:
    Pittsburgh, PA
    Vehicle:
    2008 Prius
    Okay everyone ..here's what happened ... I went and filled up my tank, it took 8.66, I dribbed and drabbled and put in as much as I could. Then I wrote down all my mileage and everything and away I went. I tracked my mileage and my first pip went down at 77 miles, the other two at 20 more miles. Now, I have 220 miles on down to 4 pips. I was averaging 50 mpg and now only 46. Don't know if this has anything to do with anything. Nothing has changed, driving the same distance 38 miles to work round trip. And to make matters worse, I had off on Friday so I didn't use the car all day!!! I had much better mileage before, oh, I have a total of 2255 on my car as of today. I just have to wonder why I'm losing those darn pips so early after the 1st one. I figured that I would have at least 1/2 tank left and now down to just 4 pippies. As far as putting in gas, I have the car since July and haven't been able to pump more than 8.94 into the tank. We have been running it down to 2 pips and then getting gas. The way I go to work, there is no gas stations so I'm trying play it safe. Help me out here? Marcia:)
     
  15. a priori

    a priori Canonus Curiosus

    Joined:
    Aug 14, 2007
    3,083
    407
    23
    Location:
    Chicagoland (West)
    Vehicle:
    2010 Prius
    Model:
    V
    Marcia - No need for concern on your part. It sounds like you are doing very well with a brand new car. Don't worry about what everyone else is getting for MPGs or miles on the first pip. If you were to ask those folks what they were getting for mileage their first 2,000 miles, you'd happily hear that most of them were just where you are today.

    WARNING! Don't push it! You can cause serious damage to the Prius by overfilling. Fill it up slowly (I lock it on the first notch, when possible) and only add a little bit more, if any. I've had only one fill go over 10 gallons, and I wasn't happy to have gone that long with a flashing pip! I'll normally fill up at one or two pips, and I never worry about running out of gas.

    Something may have changed. I've noticed it. If you have an early morning commute, you'll notice the cooler temperatures at the start of the day. This requires a longer warm-up for the car, and I've seen my mileage plummet these past two weeks. This doesn't mean anything for those folks in LA or Florida, but it means quite a bit to those of us in the North. Your mileage will taper off through the Fall, it will drop precipitously during the Winter, it will climb through the Spring, and it will skyrocket during the Summer (depending on your need for A/C).

    I wouldn't worry in the least, Marcia. Enjoy your great car and the fact that you are getting x times the mileage you were getting in your previous car.