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

Gliding in B mode

Discussion in 'Gen 2 Prius Fuel Economy' started by bestmapman, Apr 8, 2007.

  1. bestmapman

    bestmapman 04, 07 ,08, 09, 10, 16, 21 Prime

    Joined:
    Apr 8, 2007
    1,289
    242
    3
    Location:
    Kentucky near Cincinnati, OH
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    Hello, I am a new Prius owner and have read a lot on the different techniques for getting the best fuel economy. These include Pulse and Glide and Warp Stealth. On my first tank I averaged 54.7 MPG using these techniques.

    I have had my Prius for about 2 weeks and have experimented in all the different modes. I have come across something that I have not read about. I will call it B-Glide.

    Above 42 MPH I can achieve "glide" that is no indication on the energy screen at all. Essentially a blank screen. It is easily achieved just as when you are below 42 MPH in the well documented glide mode. I can always get into this "B-Glide" and it will hold it downhill for at least 120 seconds as I have used it on a 2 mile downhill stretch and was able to hold it the whole way down at 60 MPH.

    How I achieve B-Glide:

    On a downhill above 42 MPH retract the Go-Pedal all the way and reapply to enter Warp-Stealth. Once Warp-Stealth is achielved switch to B. Adjust the Go-Pedal (usually slightly more pressure) and all the energy flow indications will go out. Just as in low speed glide (below 42 MPH). The only time this will not work is if the battery is low. It seens to want to charge it one way or another then. I do not retract the Go-Pedal in the B mode as it goes into the high regen mode and slows the vehicle to much.

    My question is:

    Has anyone heard of this before.
     
    #1 bestmapman, Apr 8, 2007
  2. efusco

    efusco Moderator Emeritus
    Staff Member

    Joined:
    Nov 26, 2003
    19,891
    1,192
    9
    Location:
    Nixa, MO
    Vehicle:
    2004 Prius
    Model:
    N/A
    hmmm, no not that exactly. I'll try it out soon with CAN-View and see what's actually going on. If you can get into a warp stealth then what advantage do you feel the B-glide offers.
     
    #2 efusco, Apr 8, 2007
  3. bestmapman

    bestmapman 04, 07 ,08, 09, 10, 16, 21 Prime

    Joined:
    Apr 8, 2007
    1,289
    242
    3
    Location:
    Kentucky near Cincinnati, OH
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    <div class='quotetop'>QUOTE(efusco @ Apr 9 2007, 12:11 AM) [snapback]420074[/snapback]</div>
    In warp stealth is runs the battery down as in this mode it doesn't seem to run down the battery.
     
    #3 bestmapman, Apr 8, 2007
  4. efusco

    efusco Moderator Emeritus
    Staff Member

    Joined:
    Nov 26, 2003
    19,891
    1,192
    9
    Location:
    Nixa, MO
    Vehicle:
    2004 Prius
    Model:
    N/A
    <div class='quotetop'>QUOTE(bestmapman @ Apr 8 2007, 11:14 PM) [snapback]420077[/snapback]</div>
    Ok, I see what you're saying. I'll take a look on CAN-View, but I suspect there's still an equivalent or worse drain from the battery that's just not being displayed on the Energy screen.
     
    #4 efusco, Apr 8, 2007
  5. bestmapman

    bestmapman 04, 07 ,08, 09, 10, 16, 21 Prime

    Joined:
    Apr 8, 2007
    1,289
    242
    3
    Location:
    Kentucky near Cincinnati, OH
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    <div class='quotetop'>QUOTE(efusco @ Apr 9 2007, 12:16 AM) [snapback]420078[/snapback]</div>
    If you don't mind talking to a new guy, What is CAN-VIEW?
     
    #5 bestmapman, Apr 8, 2007
  6. efusco

    efusco Moderator Emeritus
    Staff Member

    Joined:
    Nov 26, 2003
    19,891
    1,192
    9
    Location:
    Nixa, MO
    Vehicle:
    2004 Prius
    Model:
    N/A
    <div class='quotetop'>QUOTE(bestmapman @ Apr 8 2007, 11:20 PM) [snapback]420079[/snapback]</div>
    see http://hybridinterfaces.ca

    Basicly a tool that taps into the CAN system of the car and allows one to read all sorts of data such as fuel flow, ICE rpm, MG1 and MG2 rpm, engine temps, battery voltage, charging, temp, etc.
     
    #6 efusco, Apr 8, 2007
  7. TheForce

    TheForce Stop War! Lets Rave! Make Love!

    Joined:
    May 30, 2005
    3,461
    537
    0
    Location:
    Wheelersburg, Ohio
    Vehicle:
    2006 Prius
    Model:
    N/A
    I did the test on my way home tonight and here is what I found with my Can-View

    Normal warp stealth...
    ~10A drawn from the battery
    0 Gallons per hour fuel flow displayed
    950rpm

    Glide in B mode...
    ~5A drawn from the battery
    .1 Gallons per hour fuel flow displayed
    950rpm

    This was at night with HID lights, 37 degrees and no AC.

    I would still go with warp stealth on a daily basis because its just easier to get to. I doubt that gliding in B mode would be any better. We would have to do some long distance B mode gliding to figure out the real fuel flow if there is any at all because it might actually be less than .1 gallons per hour or none at all.
     
    #7 TheForce, Apr 9, 2007
  8. barbaram

    barbaram Active Member

    Joined:
    Jan 24, 2006
    911
    70
    9
    Location:
    Trenton, NJ
    Vehicle:
    2010 Prius
    Model:
    IV
    B is for dynamic braking and I agree with the manual about not using it for extended periods of time.

    here is an explanation of locomotive dynamic braking:
    Inconjunction with the mechanical brakes, the locomotive has dynamic braking. In this mode, each of the four traction motors acts like a generator, using the wheels of the train to apply torque to the motors and generate electrical current. The torque that the wheels apply to turn the motors slows the train down (instead of the motors turning the wheels, the wheels turn the motors).

    I am certain the prius b mode is similar. The electric motors probaly are not designed for prolonged torque.
     
    #8 barbaram, Apr 9, 2007
  9. brick

    brick Active Member

    Joined:
    Dec 10, 2006
    1,083
    78
    0
    Location:
    Upstate NY
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    <div class='quotetop'>QUOTE(barbaram @ Apr 9 2007, 04:11 AM) [snapback]420164[/snapback]</div>
    Not quite. Regenerative braking is the Prius version of dynamic braking. The only difference between the Prius version and the locomotive version (except for a slight size difference) is that the Prius stores energy in the battery whereas the locomotive bleeds it off as heat via very large resistor banks. The Prius can and does use regenerative braking pretty much every time you step on the brake pedal normally. The mechanical brakes kick in only under high braking loads and at very low speeds. The motors can keep up with it just fine but the current load into the battery is limited.

    B mode is more like engine braking in a regular car. Engine braking spins up the ICE and uses it as an air pump, slowing the car down via internal friction. (The wheels turn the engine which pumps and compresses air which bleeds off energy to slow the car down.) As such, most of the time there's nothing to be gained by using it because it wastes energy that otherwise might have gone toward regeneration.
     
    #9 brick, Apr 9, 2007
  10. bestmapman

    bestmapman 04, 07 ,08, 09, 10, 16, 21 Prime

    Joined:
    Apr 8, 2007
    1,289
    242
    3
    Location:
    Kentucky near Cincinnati, OH
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    Thank you for theses coments, but I undrstand that the extra braking in the B mode only applies when the Go-Pedal is fully retracted. If a glide mode exists in "B" that does not exist in "D" it may be useful. If someone who has the CAN-View could document what is happenning it would be helpful.

    Additionally, alot of people have stated that "B" is for braking and leave it at that. I have not found anywhere where anyone has used the CAN-View to fully document what is happenning in "B" in the complete range of operation. This may be useful also.

    One last thought, I can't seem to find any documentation as to what is happenning in the "N" mode. Maybe it is just my natural curiosity but I would like to know what is disconnected and what happens. I have found several detailed explanations of the PSD. These were very written and well documentated with great graphics. Could someone point me in the right direction here.

    Thanks
     
    #10 bestmapman, Apr 9, 2007
  11. efusco

    efusco Moderator Emeritus
    Staff Member

    Joined:
    Nov 26, 2003
    19,891
    1,192
    9
    Location:
    Nixa, MO
    Vehicle:
    2004 Prius
    Model:
    N/A
    <div class='quotetop'>QUOTE(bestmapman @ Apr 9 2007, 09:46 AM) [snapback]420235[/snapback]</div>
    Look above, TheForce documented your "B-glide" on CAN-View. There is fuel burn even though battery draw is a little lower so it is less efficient than standard hyperstealth.

    N completely disengages the ICE from the PSD...it's well explained in a number of places. The ICE, if it was spinning when you go into N, will continue to spin and burn fuel. If it was not spinning then it will not start spin since it's disengaged from MG1 so it can't be started.
     
    #11 efusco, Apr 9, 2007
  12. bestmapman

    bestmapman 04, 07 ,08, 09, 10, 16, 21 Prime

    Joined:
    Apr 8, 2007
    1,289
    242
    3
    Location:
    Kentucky near Cincinnati, OH
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    Thank you for your patience. I feel like I am back in Freshman chemistry in 1973 asking all the questions that the professor gets every year.
     
    #12 bestmapman, Apr 9, 2007
  13. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,074
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    <div class='quotetop'>QUOTE(bestmapman @ Apr 9 2007, 12:20 AM) [snapback]420079[/snapback]</div>
    Just a point of clarification for new readers: CAN stands for Controller Area Network and is a network used for communicating between computer controllers in automation and automotive applications. It is sort of like Ethernet for automation. CAN-VIEW is a protocol analyzer that taps into the CAN network on the Prius and lets the user eavesdrop on the communication between all of the ECUs, so you can see what the brakes are saying to the engine and so forth.

    Tom
     
    #13 qbee42, Apr 9, 2007
  14. efusco

    efusco Moderator Emeritus
    Staff Member

    Joined:
    Nov 26, 2003
    19,891
    1,192
    9
    Location:
    Nixa, MO
    Vehicle:
    2004 Prius
    Model:
    N/A
    Wanted to add that I've confirmed TheForce's results. I found it easy to get the amperage drop into the "no arrows to/from battery" condition with about a -3-5 amp draw showing on a over-42mph B-glide, but there was clearly ICE running and 0.1 fuel flow.

    I'd conclude that despite being easier to get into a no-arrows condition that the reality is that fuel is being burned more so than in a hyper-stealth glide.

    That said, this may be a good way for those with lots of long downhills who have trouble getting into the hyperstealth glide above 42mph to go...the fuel burn is minimal and it's easy to avoid battery use. So I think this is a good addition to the literature of hypermiling.
     
    #14 efusco, Apr 10, 2007
(You must log in or sign up to post here.)