Do I really get 99.9MPG with engine running?

Discussion in 'Gen 2 Prius Fuel Economy' started by mikepaul, Feb 5, 2004.

  1. mikepaul

    mikepaul Senior Member

    Joined:
    Dec 2, 2003
    1,763
    6
    0
    Location:
    Columbia, SC
    Vehicle:
    2004 Prius
    So I'm driving around, and glance down at the Energy Monitor, and it shows the engine providing power to the wheels and to the electric motor which is sending some to the battery, at 99.9MPG.

    This is rather counter-intuitive. I'd think if the engine is running, odds are I'm using fuel. The two go together. When I'm warming the car up, I see the Consumption MPGs go down, so I know that is working properly.

    I do see MPGs between 50 and 99 all the time, going down the road as fast as 75MPH. A small downhill slope, and the MPGs shoot through the roof for a short duration. What I don't understand is how the engine can be powering the wheels and still I get 99.9MPG...
     
  2. Wolfman

    Wolfman New Member

    Joined:
    Nov 28, 2003
    1,233
    17
    0
    Location:
    Williston, ND.
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Yes, it's possible. The requirements to move the car are at a bare minimum on a downhill run, yet the hill isn't long enough to allow the ICE to shut off. The concept is really no different than coasting downhill in a normal vehicle.
     
  3. olends

    olends New Member

    Joined:
    Jan 1, 2004
    214
    1
    0
    Location:
    Clifton Park, NY (near Albany)
    also at 75 mph, the ice must spin, albeit using no fuel, and under no compression, just to prevent a mechanical overspin of MG2.

    and a mechanical overspin of an electric motor= way way way above redline on an ice, and we all know over red line is BAD
     
  4. mikepaul

    mikepaul Senior Member

    Joined:
    Dec 2, 2003
    1,763
    6
    0
    Location:
    Columbia, SC
    Vehicle:
    2004 Prius
    I'd like an update for the display software, so the little ICE visibly vibrates when it's running. You''d pull up to a light and it'd be vibrating, then you'd feel the ICE cut off and see the display 'shut off' too.

    Just seeing the animated lines isn't quite informative enough for me...
     
  5. xevious

    xevious New Member

    Joined:
    Jan 19, 2004
    187
    2
    0
    Location:
    Oregon
    Another thing to keep in mind is that the display reads "99.9" whenever the calculated mileage is equal to or greater than 99.9 MPG. When in stealth mode, your instantaneous MPG is actually hovering somewhere near the outer reaches of infinity (that is, the "miles" figure is accumulating while the "gallons" stay in the tank), so the 99.9 is way off in this case.

    When the display reads 99.9 with the ICE running, your actual MPG could be 101, 120, 200, or higher. Point is, the impact on fuel consumption is minimal and (according to the ECU) you are indeed getting at least 99.9 MPG.
     
    tanglefoot likes this.
  6. Wolfman

    Wolfman New Member

    Joined:
    Nov 28, 2003
    1,233
    17
    0
    Location:
    Williston, ND.
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I actually got a surprise on the way home yesterday. I was driving a downhill stretch of road that I had always asumed that the engine had cut off due to the maxing out of the graph, and the steepness of the grade. I was surprised to find out when I switched over to the energy monitor to find the engine running, and supplying power, electric motor running, supplying power, AND power being drawn off of the battery. The climate control system was off, as I only run it just enough to clear the windshield in the mornings.
     
  7. jeffrey

    jeffrey New Member

    Joined:
    Jan 12, 2004
    94
    0
    0
    Now that its warming up a bit here in New England, I've noticed that on my consumption screen I've actually received three five minute periods of 99.9mpg in the last couple days. Generally I seem to get five minute intervals of just over or under 50, ranging from a low of 35ish (first five minutes of the run) to fairly steady five minute blocks of 45-55. Then, all of a sudden, I'll get a block of 99.9. I guess I'm wondering why not 85, or 75, or 95. It seems I don't get any blocks of anything much over 55 or so, unless I get one of these (relatively new) 99.9 anomolies.

    Anyone have any thoughts, or observe anyting similar?

    Peace :)
     
  8. cybele

    cybele New Member

    Joined:
    Dec 5, 2003
    406
    1
    0
    Location:
    Los Angeles
    I get intermittant blocks of 60, 75 or something that I figure is 85 or 90. I guess it all depends on the math. Those are usually stretches where I get a lot of 99.9 and then a few brief periods of acceleration to get to cruising or coasting speed (which is why I guess it would average to less than 99.9).

    But it's much warmer here ... my morning commute starts at anywhere between 48 to 55 degrees and then in the evening it's usually around 55 to 70 degrees. I do much better on my evening commute, even though it's pretty much uphill.
     
  9. daniel

    daniel Cat Lovers Against the Bomb

    Joined:
    Feb 25, 2004
    14,487
    1,512
    0
    Location:
    Spokane, WA
    Vehicle:
    2004 Prius
    I was cruising around a parking lot for ten minutes at 6 mph, hoping someone would leave so I could park. As it was a rare warm (35-degree) day and the car was warmed up and the heater was off because the bright sun was keeping the cab warm, the car stayed in stealth mode the entire 10 minutes. By the time I gave up and left, I had two 5-minute segments of 100 mpg and my battery was at about half.

    It was cool because it was the first time I'd been able to turn the heater off, and so was the first time I'd seen extended stealth mode.

    I wonder if pedestrians can tell that the engine is not running. My dealer tells me there are 4 other 2004 Prius in Fargo. I've never seen any of them.
     
  10. USK

    USK New Member

    Joined:
    Mar 10, 2004
    24
    0
    0
    Location:
    Choshi, Japan
    I think ,
    it shows the engine providing power to the wheels and to the electric motor which is sending some to the battery.
    There are the two occasions.
    The One is the full power with bad mpg.
    The next is the high speed (over 42 mph ) motor mode when the engine start to need with no power because the THS System limitation.
    It may be over 150 mpg. in Japanese monitor about over 65 Km/L , so not 99.9.

    _______________________
    USK Bordeaux mica 2001
    20,668.29 miles / 353.55 ga. = avg. 58.5 mpg 3/5/04
     
  11. JasonS

    JasonS Jason Siegel

    Joined:
    Dec 20, 2003
    53
    0
    0
    Vehicle:
    2004 Prius
    Is it possible your screen got "stuck?" On one trip the mileage wouldn't update for a minute or two even when I revved the engine or came to a stop.
     
  12. CrazyLee

    CrazyLee Member

    Joined:
    Aug 3, 2014
    151
    23
    0
    Location:
    Muskegon, MI USA
    Vehicle:
    2004 Prius
    Model:
    II
    Hi Guys.

    The mileage will climb to very high numbers when 99.9 shows. That number is what Toyota chose to limit the display.
    My DynoDash SPD will show the ACTUAL MILEAGE at any time. (DashDyno isn't hybrid capable, standard OBDII only.)
    I got it before I got my 2004 Prius.
    I am going to buy this one. Tachyon H1 OBDII Scan Tool for Toyota Hybrids | Tachyon Technologies
    My Mini VCI won't work anymore, can't connect to ECU.
    I was surprised to see over 7000 mpg showing, momentarily until the calculations showed 6000 mpg + in EV mode.
    The mpg will jump all around like this until the engine resumes power output. Then it goes to a "normal" MPG.

    Over 41 mph , engine spinning, on slow down will get 250 mpg up and down mpg in EV mode, coasting or regenerating, the engine is spinning and not driving the car.

    I don't know what actually happens when the engine does this.
    Maybe the engine valves are cut off making the engine not pump air and not causing pumping losses.
    I haven't seen info this does happen though.

    It is amazing they actually spin the engine like this!

    It doesn't seem to slow the car quicker than when I am in a coasting mode.

    Keep up the GOOD Mileage
     
  13. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    82,237
    35,720
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    what is the actual mileage when your sitting with the engine running? and when your gliding with the engine off? tia!
     
  14. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    11,744
    5,953
    0
    Location:
    Greenwood MS USA
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    (It has been 11 years since anyone typed in this thread)
     
  15. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    82,237
    35,720
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    did we break a record?:cool:
     
  16. Mendel Leisk

    Mendel Leisk Obtuse Angler

    Joined:
    Oct 17, 2010
    35,128
    24,018
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    When did Priuschat start??
     
  17. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    11,744
    5,953
    0
    Location:
    Greenwood MS USA
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    "Founded in 2003, PriusChat has been the go-to spot for Prius, hybrid, and EV discussion for over 10 years."
     
    Mendel Leisk likes this.
  18. Data Daedalus

    Data Daedalus Senior Member

    Joined:
    Jul 6, 2013
    907
    985
    0
    Location:
    Wembley, London
    Vehicle:
    2008 Prius
    Model:
    II
    There's an approximately 2+ mile portion of my 18 mile commute to work every morning, where, coming down a rather very long downward slope at 50mph produces a reading of 99.9mpg on my MFD with the engine running, so, this is entirely possible under similar conditions :)


    Huh?
     
  19. Britprius

    Britprius Senior Member

    Joined:
    Jun 14, 2010
    5,194
    1,826
    0
    Location:
    Herefordshire England
    Vehicle:
    2008 Prius
    There is a section of the M54 motorway that on odd occasions I drive where for over 5 miles at 70 mph in cruise control where I register a continuous 99.9 mpg. The strange thing is some of this distance appears to be up hill, but I think this must be an optical illusion.
    There is a stretch of the M62 where this is readily done for well over 7 miles coming down off the Saddleworth moors towards Manchester. This however is most definitely a down hill run. This motorway is the highest motorway in the UK.

    John
     
    Data Daedalus likes this.
  20. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    82,237
    35,720
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    i have been getting 999 mpg on 65% of my driving.
     
    Data Daedalus likes this.
Loading...