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2016 Toyota Prius unveil expected soon - Lentz Speaks

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by ggood, Jun 17, 2015.

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  1. bisco

    bisco cookie crumbler

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    i'm averaging 76 mpg on the mfd today over a hundred miles or so. yes, there are a lot of prius out here.
     
  2. subjective

    subjective Member

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    A FIRST SHOWING WOULD BE "MORE CREATIVE" IF PRESENTED ON THE MOON, even if it is a simulated view. WE have waited a long time so we need a little more SPIFF than for him to tell us he likes it. IT BETTER BE GOOD!
     
  3. hill

    hill High Fiber Member

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    Pick it pick, slacker

    [​IMG]

    .
     
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  4. hill

    hill High Fiber Member

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    where's the festive barbecue?



    .
     
  5. bisco

    bisco cookie crumbler

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    treasure island?
     
  6. UsedToLoveCars

    UsedToLoveCars Active Member

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    this guy claims 63mpg is probably the upper limit for ICE engines on the highway - assuming .2 cD, diesel-like efficiency and low rolling resistance. If toyota manages say 55mpg, that's pretty impressive.

    100 MPG on Gasoline: Could We Really? | Do the Math
     
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  7. hill

    hill High Fiber Member

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    Diesel is not more efficient - it simply has more BTUs per gallon
     
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  8. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Uh, he left out transmission and rolling drag but I appreciate the model:
    We like cars because we can travel quickly from point A to point B. So let’s evaluate the energy requirements to make that journey at freeway speeds. We will use the somewhat awkward (although appropriate) speed of 67 m.p.h. because it conveniently maps to 30 meters per second. At these speeds, aerodynamic resistance is the dominant energy drain, so we will start by evaluating only this to get a lower bound on fuel efficiency, and find that we do a pretty good job!
    . . .
    How does the Prius today get a fuel economy in the low 50′s? The drag coefficient is on the low side, at 0.25. The area is small-ish—I estimate 2.5 m², and the big trick is that the engine can be optimized for freeway speeds since the battery can assist acceleration at lower speeds. Traditional cars sacrifice freeway efficiency for the get-up-and-go performance that is so important in test drives. If I use 25% engine efficiency with the aforementioned values, I get 56 MPG.

    Compared to my benchmarks:
    [​IMG]
    • 56 MPG measured
    • 56 MPG measured (using 25% engine-to-wheel efficiency)
    He goes on:

    At 30 m/s (67 m.p.h.) in air, factoring in rolling resistance: our 31 MPG sedan becomes 26 MPG; our 56 MPG Prius becomes 45 MPG;

    Now if he had included the rolling resistance, the resulting engine-to-wheel efficiency increases and should approach the higher Prius efficiency like the 31% I used with our NHW11. Regardless, he is taking the right approach. I'll join his blog and share my speed vs MPG charts to give him some data points and positive feedback.

    Thanks,
    Bob Wilson
     
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  9. telmo744

    telmo744 HSD fanatic

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    Both are true, diesel is more efficient (thanks to the high compression ratio and high volumetric efficiency) and has more BTU per gallon.
     
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  10. bwilson4web

    bwilson4web BMW i3 and Model 3

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    We should chat about this over in the diesel forum given the improved efficiency of the Toyota Atkinson cycle . . . the type of technical details I love to chat about. <GRINS>

    Bob Wilson
     
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  11. austingreen

    austingreen Senior Member

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    He did a lot of work for nothing. He could have just looked at what is out there. VW has the XL1 (europe only) with half the cdA and rolling resistance of the gen III prius. We only have nedc figures for it at 261 mpg. Nedc is inflated, because it doesn't test charge sustain mode, how well the car would do after the battery no longer has plug power. Still it can easily exceed 100 mpg with its 2 cylinder diesel.

    We can guess a 3 cylinder atkinson with prius engine efficiency (38%)would get about 100 mpg in that car. I'm sure you would redesign the gearing for the lower torque engine, and change the software as it would not need battery assist as often being higher horsepower.

    +1
    Telmo is quite right here. The typical vw diesel gets 42% peak thermal efficiency while the gen III prius engine gets 38% and the rumored gen IV is 40%. In the lab turbo di gasoine engines get up to 47% efficiency, while real world diesels get 50%, and a proffesor at University of wisconsin has a diesel hybrid engine runing at over 59% efficiency that uses gasoline and diesel at different power levels.

    Still it should not escape us with a hybrid drive both gasoline and diesels can work closer to their peak efficiency, nullifying much of the diesels advantage. Given the added cost and weight, it is likely more economic to add a bigger battery and a plug than a diesel to a hybrid. That is why even vw and bmw, diesel champions choose gasoline engines in their hybrids and plug-ins.
     
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  12. Jeff N

    Jeff N The answer is 0042

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    And it has more BTU per gallon because it has a higher ratio of carbon to hydrogen atoms which in turn means it inherently emits more CO2 per gallon when burned.

    Can a Diesel engine run with a higher enough efficiency versus a gasoline engine to make up for the inherent difference in carbon per gallon of fuel?

    The old answer used to be yes but that not necessarily true anymore with high thermal efficiency Atkinson cycle gasoline engines, eCVTs, and full hybridization.

    On the other hand, it doesn't really matter as long as both Diesel and gasoline engines are made to be efficient. As long as we are using either fuel we need to keep bring up petroleum out of the ground and when it is run through a refinery it's inherently going to distill out roughly 45% gasoline and 45% diesel with a smattering of other products. The product mix can be tuned somewhat but not dramatically without making the refinery a lot less efficient.

    We need to get rid of both diesel and gasoline vehicles together or at least dramatically reduce fuel consumption by rapidly switching towards PHEVs and BEVs running on largely renewable energy. And once we get liquid fuel use down by 85-90% we can realistically switch most of the remaining PHEV and other liquid fuel consumers over to renewable fuels like cellulosic ethanol.
     
  13. Jeff N

    Jeff N The answer is 0042

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    Actually, there are standard NEDC test cycle results that measure charge sustaining fuel use without relying on grid electricity. VW just chose not to release those results because it would hurt their marketing story. For example, the 2011 Volt/Ampera is about 231 mpg on NEDC in British gallons (196 mpg in U.S. gallons) but 47 mpg on the charge sustaining NEDC test. Newer Volt's would be higher than 231/196 because of increasing EV range in later years.

    My guess is that the XL1 would get a bit over 100 mpg in charge sustaining in British gallons and 90+ mpg for US gallons.
     
  14. telmo744

    telmo744 HSD fanatic

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    Yes, agree. But don't count on me polluting the diesel forum with my particles. :rolleyes:
    Better to switch off diesels for good. :p
     
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  15. austingreen

    austingreen Senior Member

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    car and driver got 128 mpg on us gallons of diesel. I'm sure if toyota, ford, or mazda put the right gas engine in there it would get over 100 mpg, but again few would buy it with that compromised space and high cost. VW chose diesel because they wanted the highest number possible, they choosse gas in the phevs vw, audi, and porsche make to sell to the public.

    Diesels are great for reducing operating costs for trucks and buses. For cars and pollution they aren't so good.
     
    #35 austingreen, Sep 2, 2015
    Last edited: Sep 2, 2015
  16. bwilson4web

    bwilson4web BMW i3 and Model 3

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    No problem, another day, another thread, another forum.

    Bob Wilson
     
  17. telmo744

    telmo744 HSD fanatic

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    Name the place, copy the link, I'll join you with the upmost pleasure. I'm very glad to discuss these matters. :coffee:
     
  18. Trollbait

    Trollbait It's a D&D thing

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    Diesel engines are more thermally efficient than gasoline ones. There are less pumping losses by not having a throttle plate. Most diesel cars need a vacuum pump to operate the power brakes designed for a gasoline powered car.
    And Toyota has a new 2.8L diesel for their trucks that is more efficient than their Prius engines.
    Audi has a pilot plant running that turns CO2, water, and electricity into what they call blue crude, which can easily be refined into diesel. In theory, it could be make into gasoline, but they have chosen to go with microbes for renewable gasoline. Likely more efficient that way overall.

    I prefer saving the ethanol for other uses.:cool::LOL::sick::sleep:
     
  19. Sergiospl

    Sergiospl Senior Member

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    Please Mods: move this thread to the diesel section 'cause there is no urea here.
    81 MPG golf TDI! | PriusChat
     
  20. Mendel Leisk

    Mendel Leisk Senior Member

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    I wonder though, are diesels adaptable to stop-start?

    Just yesterday, we were sitting at a loooong red light, shut down, listening to the diesel truck in the lane beside us, rumbling away.
     
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