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Why the BMW i3-REx

Discussion in 'EV (Electric Vehicle) Discussion' started by bwilson4web, May 15, 2016.

  1. Trollbait

    Trollbait It's a D&D thing

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    You got to be careful when quoting a NEDC ICE fuel economy figure for a PHEV. Ease of the test, it includes use of grid electricity during the test. So a PHEV with long EV range will have this figure inflated by having the ICE run for a shorter time.
     
  2. bisco

    bisco cookie crumbler

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    can you imagine what the l.a. police will do with them. they'll probably all be sitting in field after 3 years or so. target practice? tesla is lucky they lost that bid.
     
  3. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I think the mistake was not getting the Range Extended version. LA is so huge that a single 'errand' will deplete the battery. With the range extender, the 150 miles is at least long enough the driver would make at least one donut stop. <grins>

    There is a high-speed, DC charger option that can put 80% of the charge on in 30 minutes. So if they are co-located with Dunkin and Krispy Kreme ...

    BTW, LiON battery and carbon fiber body on aluminum frame:
    [​IMG]

    FYI:


    Source: Tesla News Source

    Bob Wilson
     
    #63 bwilson4web, Jun 9, 2016
    Last edited: Jun 9, 2016
  4. El Dobro

    El Dobro A Member

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  5. bhtooefr

    bhtooefr Senior Member

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    The photo of one I saw on Jalopnik showed two flaps - the charging flap and the fuel flap.
     
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  6. DonDNH

    DonDNH Senior Member

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    Feel the Bern?
     
  7. bwilson4web

    bwilson4web BMW i3 and Model 3

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  8. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Argonne Labs does great work and makes a lot of engineering data available. So I took the best case test file, 61504060.txt:
    • UDDS protocol
    • 24 C, climate control off, hood down, windows down (on a dyno!)
    • 7.48 miles
    • 51.6 MPG (others range from 36. to 50.7, this is the best)
    Now this is just my first analysis plotting dyno kW, battery kW, and REx kW:
    [​IMG]
    • car is driving the dyno - the upper left quadrant, shows how power from the battery and REx provide the energy needed to spin the dyno for acceleration. The brief negative REx power is the car spinning up the engine.
    • car is stopping on the dyno - the lower right quadrant is when the car is braking, actually regenerative braking, and absorbing power from the dyno. This is when the REx is no longer needed so its power drops from ~7 kW to zero.
    Now I have more interesting metrics to analyze including a raw BSFC chart for the REx. I also need to take the other extreme, the worst case, and see what is going on. Finally there is a sub-freezing and +90F set of data. But there are a whole set of tests in EV-only mode. It will keep me busy. <GRINS>

    Bob Wilson
     
  9. bwilson4web

    bwilson4web BMW i3 and Model 3

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    With the Argonne data, I learned the traction battery overhead is about 540W and updated the mph vs mi/kWh chart:
    [​IMG]
    This data begins to show how sensitive the BMW i3-REx is to rolling drag effects. I intend to use the Prius trick of maximum sidewall pressure.

    Bob Wilson
     
    #69 bwilson4web, Jun 11, 2016
    Last edited: Jun 12, 2016
  10. bwilson4web

    bwilson4web BMW i3 and Model 3

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    So here is the former Prius, now owned by our housekeeper, and our replacement, BMW i3-REx:
    [​IMG]
    EPA and Mfg. metrics 2003 Prius 2014 BMW i3-REx
    1 Drive Front-Wheel Rear-Wheel
    2 HP 114 hp 168 hp
    3 Curb lbs 2765 lbs 2899 lbs
    4 Fuel tank gal 11.3 gal 2.0 gal
    5 Traction battery no plug 18.7 kWhr
    6 Passenger volume/seats 89 ft{3}/5 84 ft{3}/4
    7 Luggage 12 ft{3} 15 ft{3}
    8 MPG@65 mph 52 MPG 40 MPG
    9 $Gas to Drive 25 Miles $1.45 $1.81(*1)
    10 $Elect. to Drive 25 Miles no plug $0.94
    11 5 year savings $3000 $4000
    12 Odometer bought 49250 mi. 6440 mi.
    13 Paid $17500 $29900

    *1 - BMW approves of 89 octane, plus, but EPA uses premium. I use plus but Costco only sells regular and premium.

    Bob Wilson
     
    #70 bwilson4web, Jun 15, 2016
    Last edited: Jun 15, 2016
  11. Trollbait

    Trollbait It's a D&D thing

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    If you are willing to juggle the pumps, midgrade gas is a 2 to 10 ratio of regular to premium.
    Cheaper than paying what the stations usually ask for midgrade, but likely not worth the hassle on a car with a 2 gallon fill.

    Have you looked into 'enlarging' the tank? From what I've gleaned is that the i3 REx has the same physical sized tank between markets. For the US the amount is limited electronically, or by different venting points for the tank.
     
  12. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I'm not ready to go for a larger tank, yet:
    Yes, I've looked at it but it is low on my list of priorities. The tank is pressurized and even if a larger tank is fabricated, you need empty volume in the body. I am looking at adding a receiver hitch which would provide a place to add things that don't have to fit in the body.

    Right now, my focus is on efficiency with fully inflating the tires high on my list. This morning I repeated my 30 mph test and got 7.5 mi/kWh, no significant improvement over the pre-alignment and new tires. First at bat, fully inflating the tires. This was especially brought home when I did a 75 mph test, 3.4 - 3.7 mi/kWh. Making a car more efficient is the 'low hanging fruit'.

    In that line, other things to explore:
    1. Aerodynamic mods - the 0.29 Cd is the same as our 2003 Prius. I suspect some areo-tricks might make a significant improvement.
    2. engine efficiency - possibly some form of cooled, EGR into the air intake and; engine oil change to something better than stock BMW practices (0-20W is already approved for the 2017.)
    Bob Wilson
     
    #72 bwilson4web, Jun 16, 2016
    Last edited: Jun 16, 2016
  13. bisco

    bisco cookie crumbler

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    how is the overall interior space compared to gen3? not measurements, but your opinion.
     
  14. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Pretty much the same as the 2003 Prius. I've sat in the back and it is no better or worse than the 03 but with only two seat-belt sets, not three.

    Bob Wilson
     
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  15. bisco

    bisco cookie crumbler

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    is that smaller than 2010? i'm not familiar with 2003 space.
     
  16. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Since I've had to switch between the two:
    • sense of space - feels more open with lots of pockets. It helps to raise seat which is not as easy as Prius. Best done when outside of BMW.
    • foot wells - about the same although the Prius may have more side-to-side. It doesn't feel as narrow as the 2016. Smaller to larger: 2016 < BMW < 2010 Prius
    • rear seats - not great but not torture either. One full-size adult, OK, and two works also. So far, the dogs don't complain. Not the first choice for double-dating with another adult couple but OK for short trip.
    It has the same, short wheelbase as the 03 Prius. This means you can sense the 'wave' of the highways. Also, the steering responds RIGHT NOW SIR!!

    Bob Wilson
     
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  17. bwilson4web

    bwilson4web BMW i3 and Model 3

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    My driving huristic is changing:
    1. Fast and free - go to charging stations for free miles and survey walking area for best value bars and bookstores.
    2. Sheltered and free - again survey walking areas to find a place to enjoy the wait.
    In contrast, this Prius driver never cared about where but quality of the destination. The Prius made destination the highest priority over parking for a free 'power charge.'

    The one exception is if a quality place is along my route, I will still visit. But it is incidental to the Howl search for an EV fix.

    Bob Wilson

    Howl - Alan Ginsberg

    I saw the best minds of my generation destroyed by
    madness, starving hysterical naked,

    dragging themselves through the negro streets at dawn
    looking for an angry fix,

    angelheaded hipsters burning for the ancient heavenly
    connection to the starry dynamo in the machin-
    ery of night,
    . . .
     
    #77 bwilson4web, Jun 18, 2016
    Last edited: Jun 18, 2016
  18. bisco

    bisco cookie crumbler

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    you've gone from 'pulse and glide' to 'free my ride'. :p
     
  19. bwilson4web

    bwilson4web BMW i3 and Model 3

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    More accurately,'beyond'. <grins> I never found 'pulse and glide' to be a practical solution for ordinary traffic. It works in isolation, one car, one road, but utter nonsense when a second car shows up. Maintaining a constant kinetic energy is the simplest and most efficient method that works in all traffic. Still, there is a question of comparing "N" to i3 regeneration.

    So last night, I did a quick sanity test to compare regeneration in the i3 versus coasting in "N". If there is a difference, my very brief ad hoc test did not reveal any. The test was using a short, shallow grade, and not optimum. However, I can clearly see the difference with our 2010 Prius where "N" is significantly better over regeneration.

    My test is also looking at our i3 to see if there is something 'going on' that needs further investigation. Fortunately, I have 10 years of 2003 Prius data and can easily compare the i3.

    Bob Wilson
     
  20. bwilson4web

    bwilson4web BMW i3 and Model 3

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    So this afternoon I used my roll-down hill normally used in freezing weather. In 85F, the BMW i3 was doing 20 mph when I had to stop. Although not definitive because of the temperature, no evidence of a rolling drag problem.

    Bob Wilson