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Toyota new engines gain 10% fuel efficiency; up to 38% thermal

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by bwilson4web, Apr 10, 2014.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Now this is good news likely to show up in a new model Prius:
    Source: Green Car Congress: Toyota introducing new series of gasoline engines with gain of at least 10% fuel efficiency; up to 38% maximum thermal efficiency
    [​IMG]

    [​IMG]

    Well it looks like I've got to buy some more SAE papers. <GRINS>

    Bob Wilson
     
  2. telmo744

    telmo744 HSD fanatic

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    Great readings, I suppose...

    ;)
     
  3. kbeck

    kbeck Active Member

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    And it's this kind of thing that's going to give Gen IV Priuses 60+ MPG. If not more.

    KBeck
     
  4. spwolf

    spwolf Senior Member

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    this is very interesting, as it is two small engine series going into cheapo cars. It is KR and NR series that are already competitive in their class when it comes to consumption, so to NR to get 15% improvement and KR to get 30%, thats a lot. Toyota estimated "only" 7-8% when they introduced brand new ZR series with Valvematic.

    I guess this VVT-IE with atkinson cycle "on demand" will go into every future engine. They said 14 new engines coming in 2015 with this tech, and they announced RC-F V8 to have it as well.
     
  5. Tideland Prius

    Tideland Prius Moderator of the North
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    Nice. So they'll update engines that are currently in use (which were all introduced recently).

    In addition, VVT-iE is something that was introduced in the current generation LS (2006-present). It's only on the intake side. The exhaust side is still hydraulically actuated according to literature.
     
  6. austingreen

    austingreen Senior Member

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    I hope and expect them to do better than that in the next gen prius. The Gen III is already 38% peak thermal efficiency, and the 2.5L DI atkinson sold in some models outside the US is 38.5% efficient.
     
  7. walter Lee

    walter Lee Hypermiling Padawan

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    It sounds like both the Yaris and Prius c will be getting a boost in their EPA ratings soon:) .
     
  8. GasperG

    GasperG Senior Member

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    I can see how the future Prius engine would benefit from this.
    Today we have 10:1 compression ratio in normal engine and 13:1 expansion ratio in Prius engine, compression ratio is probably the same 10:1 to avoid knock.
    Tomorrow we will have 13.5:1 compression ratio in normal engine and something like 18:1 expansion ratio in Prius engine (compression ratio 13.5:1 knock solved).

    Does this makes sense or it doesn't work like that?
     
  9. telmo744

    telmo744 HSD fanatic

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    Yes, this increasing trend of CR may be also shifted to the Prius ICE, within limits.
    I would not bet on 15+, though.
     
  10. bwilson4web

    bwilson4web BMW i3 and Model 3

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    It is a good question as the 'modified' Atkinson cycle plays a trick:
    The compression stroke ratio is different than the expansion stroke ratio:
    • compression stroke:
      • Intake valve open on first part letting some of the fuel-air charge go back into the intake manifold. Another cylinder has already opened the intake valve and pulls this charge towards it from the intake manifold. This is done with very little energy pushing to compress the charge.
      • Intake valve closes and the piston begins compressing the fuel-air charge, roughly 8-to-1. This low compression ratio is why our Prius uses regular gas, not premium. It also reduces the energy needed to compress the fuel-air before it burns.
    • expansion stroke extracts combustion power - at 13-to-1, the hot, combustion gas pushes the piston all the way to the bottom when the exhaust valve opens. This extracts much more energy than a lower, expansion ratio, Otto engine and comes close to diesel efficiency.
    Now that fractional charge pushed back into the manifold passes by the intake valves twice and this helps homogenize the fuel-air mixture. So on the next intake stroke, this well mixed fuel-air goes in first to help reduce particulates.

    It really is a clever solution that reduces internal engine compression overhead yet lets the engine burn a fuel-air mix optimized to reduce particulate, hydrocarbon and nitrogen-oxides. What remains is handled by the catalytic converter.

    Bob Wilson
     
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  11. GasperG

    GasperG Senior Member

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    I knew the concept, but only 8:1 effective compression ratio and huge 13:1 expansion? I didn't know the difference was so huge.

    Still I would think there would be benefit from raising both this values to something like 10:1 and 16:1, with the tricks in that article, boosting efficiency over 40%.
     
  12. bwilson4web

    bwilson4web BMW i3 and Model 3

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    The expansion ratio is a complex problem. At higher power settings, the hot combustion gasses have more time to form difficult to convert, emissions compounds. Yet even our 1.8L Prius engine uses cooled exhaust gasses to keep the exhaust temperatures low enough to avoid damaging the catalytic converter yet still run a lean mixture. Also the stresses on the engine go up, which might require heavier engine parts.

    In contrast, the compression stroke ratio is limited by fuel octane rating. Too much and we have to start running premium. To get more power, it is probably better to increase the displacement and not switch to premium fuel.

    Bob Wilson
     
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  13. Trollbait

    Trollbait It's a D&D thing

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    The article doesn't mention direct injection, but that would allow higher compression with regular octane. Mazda's SkyActiv-G is 13:1 with US regular(14:1 elsewhere).
     
  14. Jeff F

    Jeff F Member

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    It strikes me that these sorts of developments threaten increased hybrid adoption, in that the fuel consumption difference between comparable hybrid <-> non-hybrid cars is likely to get smaller rather than larger. Of course the technology will benefit hybrids, but it will benefit non-hybrids more.
     
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  15. john1701a

    john1701a Prius Guru

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    It's always a moving target.

    Traditional vehicles are the true competition.

    Don't let the rhetoric convenience you otherwise.
     
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  16. austingreen

    austingreen Senior Member

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    Toyota gas cars get efficient engine from hybrids - Businessweek



    OK what is the main thrust of this new tech? Its valve control that lets them shift from otto valve timing to the timing we have in our prius, plus the very low friction coatings that are in our gen III prius may have slightly advanced and are being used on these less expensive engines.

    What do we get Gen II prius 37%, Gen III 38%, 2.5 L atkinsion with di+pi 38.5% (lexus ISh) is moving to small non-hybrid engines 1.3L up to 38%, 1L up to 37%.

    The advances mentioned that are not yet on the toyota hybrids are better intake valve and chamber design to produce a better fuel air mix, and an improved piston shape to produce a more even heating explosion. Definitely things that mazda talked about in skyactiv to improve compression ratio without detonation, are now in these Toyota engines. Maybe combined this is good for 0.5%, but should provide better torque at low rpm.

    None of this closes the city gap to hybrids. Definitely though these equalizes the playing field when on the highway in cruise control.
    Hybrid-focused Toyota turns to new fuel-efficient engines| Reuters




    The other tech we can expect from toyota in the next gen prius probably is di. They already have done it in the Lexus ISh (not available in US) and got about a 1% improvement in thermal efficiency. Going from 38% to 39.5% (1% di, 0.5% piston and airflow changes) in the next gen prius gets us closer to the theoretical thermal efficiency limit of normally aspirated engines.
     
  17. Troy Heagy

    Troy Heagy Member

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    Oh well. That is already the case in Europe where hybrids sell poorly, since EU citizens have the option of gasoline engines that are nearly-as-good in MPG but cost far less.

    Wouldn't you rather have a non-hybrid direct-injected 13:1 compression Prius C for ~15,000 rather than ~19,000 dollars?

    And yet still get the same highway MPG? I would. (Unless I lived & worked in the city... then I'd want an EV.)
     
  18. austingreen

    austingreen Senior Member

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    For the US, the 2016 small toyota replacement of the yaris (now selling very poorly because people choose the prius c), will be based on a 1.3 L skyactiv ice which should be 13:1 compression otto that can run in Atkinson mode.
    Toyota's new subcompact will use Mazda's Skyactiv engine
    Toyota's new 1.3L appears destined for europe and/or asia but not the US. Part of the lower manufacturing costs is the new mazda2/yaris replacement (don't know if it will be still be sold as yaris) is being built in Mexico and not built with more expensive labor/electricity/transportation in Japan or France.

    That should give american's that choice in Toyota's prius c versus more efficient new yaris. In Japan, with higher gas taxes, we know that the aqua(prius c) greatly outsells all non-hybrids.

    Toyota is working on new turbocharged engines but that is in different announcements for much more powerful engines. VW is the only company that has gotten cylinder deactivation on 2 cylinders to work, going to atkinson mode as mazda and honda do, is likely as efficient in these very small engines. I'm not sure how offset cylinders improves a 4 cylinders efficiency but don't quite understand all of the technique.
     
  19. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I would prefer it costs as much as full tank of gas so like some Oklahoma Native Americans, I can just abandon the car when it runs out of gas.

    Reminds me of the old joke, there are two kinds of people in the world:
    1. Those who divide the world into two kinds of people
    2. Those who don't
    Let me suggest we really want to have our cake and eat it too. We want EV-like efficiency in the City and range of a gas/diesel car on city-to-city trips. As a general rule, one can optimize either and if affordable, own two, purpose specific vehicles. But in reality, there are limits on home parking space and owning more than one vehicle become a significant burden.

    So my Prius cost per mile:
    • ~2x the cost per mile of an EV in the City
    • ~3-4x the EV range on the highway
    I don't have to choose a specific vehicle for each trip. But like any multi-function vehicle, our Prius can achieve significant savings over the wrong vehicle for the particular trip. So if I'm at work and have to go to Nashville, I don't have to spend nearly an hour to drive home to switch to the highway car. Or when I'm in Nashville, I can still drive from appointment-to-appointment without trying to rent or borrow an EV.

    Never let "Perfect be the enemy of good enough." So get a vehicle that will take a vacation but not eat up all your money at the vacation spot on fuel. So we can go to the Gulf or Atlantic and still eat an upgraded meal that otherwise would have to pay for the gas to get the meal. And when we arrive at the vacation spot, we can get a room closer to the beach because we didn't have to spend so much on fuel or stop so often that it eats vacation time on the way.

    Bob Wilson
     
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  20. Troy Heagy

    Troy Heagy Member

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