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

is 10% increase on EPA cycle realistic?

Discussion in 'Gen 4 Prius Main Forum' started by cyclopathic, Oct 1, 2015.

  1. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,850
    4,018
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    How many people buy four-door hatchbacks for sex appeal?

    If that's what you want, buy a Vette. I buy this car to haul my stuff and my family, efficiently, at modest cost, and with little or no hassle. Period.

    And Steve's changes didn't get me to buy any Apple stuff - I didn't have any before he came back, and I haven't bought any since.
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,755
    48,969
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    we're talking about glove boxes because toyota hasn't told us much else. but if you look back at the 3rd gen release, the talk was pretty much the same, 'looks don't impress me', 'don't like the bridge', mpg increase isn't as much as expected', 'handling, acceleration, soundproofing, seats aren't much better'. nothing new under the sun, you guys must be newcomers.:cool:
     
  3. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    3,292
    547
    0
    Location:
    2014 Prius c
    Vehicle:
    2010 Prius
    Model:
    II
    Well the aerodynamic resistance in city driving is negligible, and on EPA highway is less than 1/2, so you need to double for this reason. Also take into consideration rolling resistance and other parasitic losses, aero-resistance will be a portion of total on highway too. So x4 times isn't a bad approximation.
    Here is a calculator take a look: Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com
     
  4. dbcassidy

    dbcassidy Toyota Hybrid Nation, 8 Million Strong

    Joined:
    May 13, 2008
    1,581
    290
    3
    Location:
    Middlesex County, MA
    Vehicle:
    2008 Prius
    Model:
    Two
    Battery development will always be evolving newer materials, process, more power, less wgt, size, and recharge time. Costs, reliability, and recycling will also be a never ending process also.

    DBCassidy
     
  5. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    3,292
    547
    0
    Location:
    2014 Prius c
    Vehicle:
    2010 Prius
    Model:
    II
    I think EPA test still uses 55MPH speeds, and for 3200-3300lbs Prius (curb+driver) with Cd=0.25 rolling resistance and aerodrag level up at 45MPH. At 55MPH aerodrag accounts for 59.43%. And highway rating is only 45% of overall combined rating; other 55% come from city driving which is not influenced by aerodynamics. HWFET also emulates acceleration, braking, etc. A/C drag will not get 10% lower just b/c you improved car aerodynamics by 10%.

    If you ignore other aspects (A/C, weight, etc) and only accounting for rolling resistance and aerodrag, to see 1% improvement in combined rating you will need to improve it by 1/0.45 * 1/0.6 = x3 times. Add A/C, other aspect and x4 does not look that far off.

    I do not think we will see new Prius Cd <0.2 needed to achieve this goal. Reducing Cd to 0.2 will reduce aerodrag to 53.95% at 55MPH (6% reduction). Which would have <2% on combined rating.

    So there are only two logical conclusions: 1) they will not get 10% improvement; 2) they found it somewhere else (like duping EPA city rating FTP-75 test via software optimization).
     
    #25 cyclopathic, Oct 2, 2015
    Last edited: Oct 2, 2015
  6. mozdzen

    mozdzen Active Member

    Joined:
    Jan 17, 2011
    719
    295
    0
    Location:
    Phoenix
    Vehicle:
    2015 Tesla Model S
    A. New tire spec: Inflate to 44 psi.
    B. New software spec: enable cheat mode when mpg test track is detected.

    Ooops. Scratch B. VW ruined that one for us.
     
    tpenny67 likes this.
  7. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    3,292
    547
    0
    Location:
    2014 Prius c
    Vehicle:
    2010 Prius
    Model:
    II
    I am not sure that it is a real cheat like in VW, just falls into grey area.

    With CVTs and drive by wire manufacturers are known to "optimize" setting for EPA tests. If you compare many cars with auto and manual on fueleconomy.gov, autos are getting better MPG ratings than MT. Yet, independent real life tests show this is not the case.

    I suspect Toyota could let the battery run lower or use more aggressive settings for short period of time. Not really a cheat, just taking advantage of fixed duration EPA test. Driving Prius C vs Gen3, I can tell that C does better in short stop and go, but if you really get stuck it is not any better than Gen3. Yet it is rated higher in City driving than Gen3.
     
  8. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    3,292
    547
    0
    Location:
    2014 Prius c
    Vehicle:
    2010 Prius
    Model:
    II
    UPDATE: Ken is saying staff manual lists Cd,=0.24. This is a 4% improvement over Gen3, so it will give 1% overall boost to combined MPG.
     
  9. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,850
    4,018
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    Without knowing frontal area, you can't make that claim.
     
  10. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    3,292
    547
    0
    Location:
    2014 Prius c
    Vehicle:
    2010 Prius
    Model:
    II
    2016 Toyota Prius details leak in manual, returns 40 km/L
    0.48% less
     
  11. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,850
    4,018
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
  12. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    3,292
    547
    0
    Location:
    2014 Prius c
    Vehicle:
    2010 Prius
    Model:
    II
    So on JC08 Gen4 is 21.7% better than Gen3? Since JC08 is centered around city cycle, we can expect similar showings on EPA city. Even if highway rating will go up by modest 5% (4% engine efficiency and 1% aerodrag) we can expect close to 14% overall rating improvement.

    62 city/ 50 hwy

    57MPG combined??
     
  13. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    3,292
    547
    0
    Location:
    2014 Prius c
    Vehicle:
    2010 Prius
    Model:
    II
    the profile on Gen3 and Gen4 isn't drastically different, how much more precision on top of 0.5% do you need?
     
  14. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,850
    4,018
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    Your 0.5% is probably +/- 5%, at least.
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,701
    38,239
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Guilty as charged, I just came onto the Prius scene late in the 2010 model year. We managed to snag a 15 month old "new" car, about 10 km's on the odo. Something the salesmen neglected to point out, but hey, it's worked out great, knock-on-wood.

    So I wasn't aware of 2nd to 3rd gen transition, pushback, that sort of thing. But I can imagine it. Was it as vehement as the current debacle, do you think?

    If there is this sorta tearing-and-healing of expectations with each generation, it's debatable that we're actually progressing, that it's becoming a "better" car. It's evolving, that's for sure.

    One thing, that's largely unspoken I think: the Prius is a BIG part of our lives, more so than a regular car. And when Toyota comes along willy-nilly with a new rendition, that just might bomb, there's consternation, justifiable I think. Well, unless we wean ourselves.
     
  16. giora

    giora Senior Member

    Joined:
    Aug 28, 2010
    1,966
    730
    0
    Location:
    Herzliya, Israel. Car: Euro version GLI
    Vehicle:
    2013 Prius Plug-in
    Model:
    N/A
    This proves (again) that you cannot make a reasonable judgment and build theories on partial facts.
    This whole thread should have been titled: What you anticipate (wish/unwish) will be the EPA rating of Gen 4 - place your bet here.
    Not more than a betting game (which is fine - as a game).
     
    bisco likes this.
  17. cyclopathic

    cyclopathic Senior Member

    Joined:
    Apr 15, 2011
    3,292
    547
    0
    Location:
    2014 Prius c
    Vehicle:
    2010 Prius
    Model:
    II
    Well we don't really know until official EPA numbers are out.

    I am not hang up on numbers one way or another, just trying to understand if it is possible, and where it comes from.
     
  18. civicdriver06

    civicdriver06 Active Member

    Joined:
    May 27, 2009
    797
    324
    0
    Location:
    Germany
    Vehicle:
    Other Non-Hybrid

    Those numbers in the manual are definitely wrong !
    Why would they decrease max . system power output ?
    To get better fuel economy?
    The new Toyota Auris Hybrid refresh in Europe allready gets 3.6 Liters on 100 Km which is about 65 mpg,but since European cycle is a bit unrealistic ,it would probably about 54 mpg US rating .
    So if even the "old" HSD with 136 hp is capable of getting quite realistically 54 mpg,,why would it take such a downsize of the power train to squeeze just one more freaking mpg out of the vehicle ?
    We will have to wait and see what happens on Oktober 29.,but I am quite sure I'm right !
     
    #38 civicdriver06, Oct 2, 2015
    Last edited: Oct 2, 2015
  19. giora

    giora Senior Member

    Joined:
    Aug 28, 2010
    1,966
    730
    0
    Location:
    Herzliya, Israel. Car: Euro version GLI
    Vehicle:
    2013 Prius Plug-in
    Model:
    N/A
    The Auris HSD is a smaller and lighter vehicle, isn't it?
     
    #39 giora, Oct 2, 2015
    Last edited: Oct 2, 2015
  20. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,755
    48,969
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    perhaps we're a more passionate bunch, or perhaps it's like this on every car site, idk. but with prius, it's hard to improve on perfection, so expectations may be a bit unrealistic. if you took everything everyone wanted in all these threads, you'd need a gazillion models.
     
    giora and Mendel Leisk like this.