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Honda Accord Hybrid: 50 MPG City - clone Toyota

Discussion in 'Honda/Acura Hybrids and EVs' started by bwilson4web, Sep 8, 2013.

  1. austingreen

    austingreen Senior Member

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    Ford appears in their implementation of the psd, to allow for high speed ice off operation. I would guess toyota would do a similar small design change instead of adding a clutch, unless they have a big battery phev with the same drivetraine. At the low power levels of mg1 in the prius, extra losses from spinning it should be low, but in a more powerful implentation like the hihy a clutch may be helpful.
    The accord hybrid system seems like a fairly elegant solution. At low speeds it is a serial hybrid, which should be extremely smooth like an bev (but noise will be similar to camry hybrid, and disjointed from speed). At higher speeds it will act like a very efficient car in top gear, but with a possible electric boost for power, instead of down shifting. The big question is did they make the gear ratio right. My guess is this thing is geared properly for 50mph-70mph, and should be very efficient here. If someone is primarily at 35mph or 45mph roads this may not be a good fit. YMMV.
     
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I wish I could but I've been in the world of 'observations' too long:
    [​IMG]
    At '20 hp', the 2003 Prius is going to be running about 65 mph, not the speculated 20 mph. I don't fault the model just the assumption of 20 mph is really, really wrong.

    If you would like to rework the model at any speed over 42 mph, I would be happy to provide Graham mini-scanner data for flat, no wind, steady state. But you are going to be at least 8 HP from the engine.

    Below 42 mph, the car will cycle between:
    • engine-ON -> charging battery and sustaining speed
    • engine-OFF, traction battery -> sustaining speed
    Please understand I don't fault your model but it does not include the dual-mode, hybrid laws below the hybrid threshold speed. To even begin to approximate your model, I would have to find a hill of the exact grade to match the assumptions.

    So at 20 mph, the car drag energy requires 3 hp. So what we need is a grade steep enough that a 3,000 lb. car will require 17 hp to sustain the climb . . . and the assumption the hybrid control laws are suspended.

    Rework the model for speed above 42 mph and we can validate the model with field observations.

    Bob Wilson
     
  3. austingreen

    austingreen Senior Member

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    Bob you understand physics, right? Pick your acceleration. 20 hp will accelerate a 3000 lb car like the prius 0-60 in over 30 seconds. I am not sure how fast you accelerate, but to me this feels quite slow;)

    Kenectic energy = 1/2 mass times velocity squared.
    There are losses that requires more energy to get to speed.
    power x time = Energy.

    Now your chart seemed to show steady state, which I rarely go at at 5 mph. At steady 5mph the prius or accord hybrid will be using very little power, and likely drawing from the battery, then cycling the ice to charge it. This uses mainly the electrical path;)

    Please plug in any numbers you read off your scan gage for engine rpm and power, then plug them into the formula, i gave you to convert rpm and torque to power. The power split is dependent on mg1 and ring gear rpm. The power split is not constant.
     
  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I don't use 'feelings', just metrics. In one respect, it makes my 36 year marriage to the same woman confirmation that she is 'brighter than the average bear.' . . . or cougar. <grins>

    Like I said, I don't fault the math model. Just in the range given, it assumes a continuous 'reality.' Sad to say, the example given doesn't conform to real world data and what little I've learned about the Prius control laws.

    I'm not kidding, it took me nearly two years before I finally understood enough to say I understood some of what is going on in the PDS. Debugging Prius control laws requires understanding at least two sets of discontinuous equations and I'm pretty sure no one outside of Toyota (including me) has a solid model . . . yet.

    You have pointed out, correctly, that the Honda Accord requires a larger engine and electrical system than the Prius. But whether this is because they want to meet the 10 second, minimum 0-60 time required but the jerks at Consumer Reports . . . well let's say I'm leaning that way. I don't think it is needed for efficient driving. Worse, it will lead the foolish to finding their "your mileage may differ" is a bitter pill.

    Bob Wilson
     
  5. bisco

    bisco cookie crumbler

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    right, i don't think they were looking for 30k accord at 27k, just a more stripped down camry like version for people who want the hybrid at a lower price point. i don't have any idea how many of each package toy sells. we didn't buy the base because of the lack of power seat.
     
  6. hill

    hill High Fiber Member

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    you could have fooled me because I think I took this picture at work about a month ago ... and maybe posted it here on this forum in another thread the same time frame ;)

    [​IMG]

    I'm just sayin' ...
    BTW, the owner let me test drive and I felt no more comfortable/uncomfortable in its drivers' seat than then I do in the generation II & III Prius. And as I've mentioned before - height wise - I'm about 6'-5" tall. normally I don't argue seat comfort because it's subjective - some will find one seat horrible the other finds it to be just fine. Sothe people who think their comfort situation matches everybody else .... well they just don't get it.
    .
     
  7. austingreen

    austingreen Senior Member

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    Nice I gave the metrics 20hp results in 0-60 at slower than 30 seconds. This feels slow to me, but some on this board seem to trickle acclerate. If you look up the prius bsfc, you will find 20hp (about 15 kw) is at the lower end of the efficient range of the gen III prius. In gen II, you need to add more acceleration than this to be efficient, as it falls bellow the most efficient range. Still I don't want to prejudge your personal preference, use your own numbers read from the scan gauge or other instrumentation. The higher the acceration (power) the higher the engine rpm if the ice is on. The higher the ice rpm the less efficient the hsd transmission will be at low speeds, but this is made up for by having the ice more efficient.

    No assumptions except that frictional losses do not greatly affect the power split. The power split is not constant as the torque split is in the hsd. Again the proportion of power, ignoring differences in frictional losses going to the wheels and mg1 is

    0.72 (rpm ring gear)/ (0.72 (rpm ring gear) + 0.28 (rpm mg1)).

    Control laws decide how much power the ice provides and how much is sourced or sinked from the battery, and this does not matter for this equation, that comes out of the simple physics of the hsd. The rpm of the ring gear is set by the speed of the car. The rpm of the ice is determined by the control software of the prius, and the rpm of mg1 is determined by the speed of the car and speed of the engine. Things are fairly straight forward here, and you can read off the bsfc chart the likely rpm/torque line and determine rpm from power.
     
  8. Trollbait

    Trollbait It's a D&D thing

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    The plug in has been available since the beginning of the year or so in two states, yes. The plain old hybrid isn't out yet, which is what the fuelly entry seems to imply.
     
  9. cycledrum

    cycledrum PSOCSOASP

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    I believe they were referring to Accord Hybrid, not plug-in in response to some dude on Fuelly.com whose got his 28 MPG 2013 conventional Accord listed as the Hybrid.

    The Hybrids are probly on going on rails out of Ohio pretty soon.

    btw, would be interesting to see a pic of you in 2nd gen with dr. seat reasonably upright. How does your head not hit the roof? Several people helped me get stuffed into cwerdna's 2nd gen at a meetup. Was pretty obvious I didn't fit well in it.

    It's all personal though, one person's trash is another's treasure.
     
  10. cycledrum

    cycledrum PSOCSOASP

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    Picture of 2014 Accord Hybrid trunk which loses 3 cu ft off non-hyb Accord. Trunk should have a full span of width since 12V battery is under the hood (Fusion Hybrid trunk narrowed due to side walls).

    Also a good review here -

    2014 Honda Accord Hybrid [w/video] First Drive - Autoblog


    Accord Hybrid trunk pic.jpg
     
  11. cycledrum

    cycledrum PSOCSOASP

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  12. cycledrum

    cycledrum PSOCSOASP

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    Prius seems to thrive in slow and stop and go traffic. In high 60 to 70 F temps, summer fuel, dry, level roads near sea level I routinely get home after 28 mile r/t trip with high 50s mpg, maybe 60 on gage for about 54 or 5 actual. This car loves slow and go, stop and go, stop lights to get higher MPGs

    MPGs are less if sailing at 65 MPH to work. Then it's 'only' 53 or 4 ish on gage. Winter blend fuel and low temps on the way though.

    Hopefully HAH can thrive in stop and go too.
     
  13. cycledrum

    cycledrum PSOCSOASP

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    "In "average" driving with no jackrabbit starts, no last-minute braking and strict adherence to speed limits, the top-of-the-line Accord Hybrid Touring we drove over a 47-mile combination city-country route returned 49.1 mpg overall....

    But in a pair of much shorter drives near the University of Texas San Antonio campus, two other 2014 Honda Accord Hybrid models didn't fare as well. On a 9.2-mile run we attained just 41.8 mpg in a midlevel EX-L, while the lighter base EX over a slightly truncated 8.6-mile version of the same route delivered 42.9 mpg. Fuel efficiency on those drives suffered a little from an abundance of small hills that kept the two-motor hybrid system from really strutting its stuff...


    there is no actual transmission, CVT or otherwise. The electric motors do the job.."

    2014 Honda Accord Hybrid First Drive on Edmunds.com
     
  14. cycledrum

    cycledrum PSOCSOASP

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    "And here's the takeaway from our test-drive: We easily hit that vaunted 50 mpg mark without really even trying. In fact, after spending hours in the new Accord Hybrid and driving on a variety of roads, we averaged fuel economy in the low 50-mpg range. Our initial experience was, like the Accord itself, seamless and natural. We didn't have to "hyper-mile" to achieve 50 mpg by sweltering in the Texas heat with no A/C or by babying the throttle. We just drove normally and the Accord's hybrid powertrain figured out the rest."


    2014 Honda Accord Hybrid First Review: Hitting 50 mpg and Beyond - Kelley Blue Book
     
  15. bisco

    bisco cookie crumbler

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    that trunk looks similar to hycam, but i cannot find hyacc specs anywhere.
     
  16. cycledrum

    cycledrum PSOCSOASP

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    I've seen

    13.1 cu ft. (TCH) vs 12.8 (HAH) listed in a review.
     
  17. telmo744

    telmo744 HSD fanatic

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  18. cycledrum

    cycledrum PSOCSOASP

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    Does the 21.6 cu ft Prius space refer to the area with rear seats upright? If you crammed the area full up to the roof, then it seems you'd be subject to projectiles that could fly into the front seats in a forward collision, unless securely tied down with a cargo net. How many use a cargo net or ropes?

    Any trunk offers secure, always hidden storage space. A hatchback's cargo is only as secure as the tie-down method.

    Also, if you leave your car with something of value in cargo area, how much area is available underneath the tonneau cover?? It doesn't seem to be even 10 cu ft as the load floor is high.
     
  19. cycledrum

    cycledrum PSOCSOASP

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    • "There are some downsides to this latest Prius, however. Most concern the interior, such as too many cheap-feeling plastics, an awkward driving position and the lack of an iPod adapter on most models." -- Edmunds(2011)
     
  20. zhenya

    zhenya Active Member

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    This is true and if Toyota or someone else offered a really good cargo barrier like we have in our Volvo's I'd buy one. That said, not every load is necessarily a projectile. A hatchback can swallow many loads that are entirely not possible in a sedan, yet too large to practically leave the cargo area in a colission.