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Featured Gen 6 Prius engine will be a “game changer,” achieve a 53% thermal efficiency

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by Gokhan, Jun 7, 2024.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Back of the envelope:
    upload_2024-6-14_1-41-2.png
    • 1.43 gal/100 mi = 1.9 * (40% / 53%)
      • ~77 MPG
    • 1.36 gal/100 mi = 1.8 * (40% / 53%)
      • ~74 MPG
    This improvement could be used to extend the range or lighten the vehicle. A lighter vehicle will get slightly higher MPG. Regardless, it will make the Prius more affordable to operate. Meanwhile, this Tesla owner is not tempted:
    • Absence of Full Self Driving - safety first as no hearse has a roof rack.
    • Relative cost to operate:
      • City largest number of miles, 50 weeks per year
        • $2.50 / 100 mile - Tesla (not including ~15% free charging)
        • $4.29 / 100 mile ~=(1.43 gal/100 mile) * $3.00 / gal - best estimated, 77 MPG
      • Highway lower number of miles, 2 weeks per year
        • $7-9 / 100 miles - Tesla
        • $4.29 / 100 miles - best 77 MPG
    Of course your mileage may vary as well as the ratio of City miles to Highway miles. Your money and your requirements.

    Bob Wilson
     
  2. telmo744

    telmo744 HSD fanatic

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    It is not mass related, it is surface area related.
    Because of the cube-square relation, surface area increases slower than volume. Making a cylinder four times larger, it only doubles the cylinder's total surface. Remember, it is one of the biggest heat losses during compression/expansion strokes.
     
  3. Gokhan

    Gokhan Senior Member

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    Does that even work? Neither the IIHS nor CR thinks so. Moreover, I believe it costs $15,000 extra—more than the price of a used car. With the high repair and frequent-tire-replacement costs of BEVs and the $15,000 extra upfront, I think it would cost a lot more to own a Tesla. It's not to mention the low resale value.

    I guess you're thrilled about Elon Musk getting his $56-billion pay package.
     
    #123 Gokhan, Jun 14, 2024
    Last edited: Jun 14, 2024
  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    All good questions, so let me answer from my 5 years, 135,000 mi Tesla and ~60,000 mi BMW i3-REx experience:
    • "Does that even work? Neither the IIHS nor CR thinks so." - did they test Version 12.3.6 that I've been driving for the last 10 days with over 2,000 miles and nearly 30 hours?
    • "I believe it costs $15,000 extra" - Recently Tesla dropped the purchase price to $12,000 and also offers a lease or subscription. Since I bought mine in Oct 2019 for $6,000, I haven't really worried about it.
    • "more than the price of a used car" - feel free to get an estimated cost for my 2019 Tesla Model 3 Standard Range Plus with 135,000 miles and some body scratches.
    • "With the high repair and frequent-tire-replacement costs of BEVs" - the OEM tires were only good for ~36,000 miles. I replaced the rims and run Bridgestone ECOPIA tires for my 3,800 lb car. I've only had one pair of Bridgestones wear out. The second pair is on the rear and still going good. As for repairs, all the warranties are done so I do my own maintenance. So far, only the ordinary car stuff has needed work.
    • "I think it would cost a lot more to own a Tesla" - the same is true with any make or model. For example, a 'non-technical' owner of a 2006 Prius recently approached me about her dealer experience. I had to defer as I've only owned a 2003, 2010, and 2017 Prius. The 2017 Prius Prime was traded in for the Tesla.
    • "low resale value" - Does not apply to me as I run my cars 'until the wheels fall off.' Actually until the repair cost exceeds my interest in the car.
    Teslas and BEVs are not for everyone. Heck, last year I bought a used 2017 BMW i3-REx with 58,000 mi from a Florida Toyota dealer for $15,000. We both think we 'stole' the deal from the other. That BMW now has over 65,000 mi and is my 'going for groceries' car.

    If anyone feels an interest in an EV, I recommend the BMW i3-REx, 2017-2018 model years. Mine benchmarked 106 mi EV and 88 mi gas range. In the $15,000 range, they are a great way to learn how to drive an EV yet still have highway privileges at 70 mph. I don't follow the latest PHEV models and have no opinion about them with one exception, do not get the low trim, 2017 Prius Prime . . . it pissed me off.

    I am happy the stock won't crash: https://ir.tesla.com/press-release/tesla-releases-results-2024-annual-meeting-stockholders

    AUSTIN, TX, June 13, 2024 – At today’s Annual Stockholders’ Meeting, Tesla stockholders overwhelmingly approved the ratification of the 2018 CEO Performance Award and the redomestication of the Company to Texas. Tesla has submitted all filings to effectuate its conversion into a Texas corporation and can confirm that the Company is now incorporated in Texas.

    Full voting results for its 2024 Annual Meeting of Stockholders are below. . . .

    Tesla is no longer incorporated in Delaware so the same Judge won't get another chance. The appeal will likely go forward. I have no problem if Tesla abandon's Delaware.

    Bob Wilson
     
  5. telmo744

    telmo744 HSD fanatic

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    Did you experience the wheel falling off a 2017 Prius Prime? :p
     
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  6. Isaac Zachary

    Isaac Zachary Senior Member

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    You're probably right. Although if you go back in time far enough diesels actually produced less NOx than comparable gasoline powered vehicles from that time period, especially before the invention of the three-way catalytic converter and also on cars with failing three-way catalytic converters and other emissions equipment.

    A +50% efficient engine that gets modern emissions is worthy of appreciation. If only newer cars were more affordable and more engaging to drive. I'm very tempted to go pick up my 1985 VW Golf diesel and start driving it again instead of the Avalon, and I'm not the only one in the family that has those feelings.
     
    #126 Isaac Zachary, Jun 14, 2024
    Last edited: Jun 14, 2024
  7. bwilson4web

    bwilson4web BMW i3 and Model 3

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    • "Does that even work? Neither the IIHS nor CR thinks so." - did they test Version 12.3.6 that I've been driving for the last 10 days with over 2,000 miles and nearly 30 hours?
    The latest version of Tesla software and Full Self Driving is down loading now, June 14, 2024, 8:00 AM. Have IIS or CR already tested it?

    Bob Wilson
     
  8. Trollbait

    Trollbait It's a D&D thing

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    The original Insight had that lean burn in 2000, and it past emissions.

    Figures 2 and 3 of that paper shows Toyota needed hydrogen injection to reach those low NOx levels.

    The paper itself didn't discuss emission levels, but they weren't studying emission controls. Lower cylinder temps of lean burn mean less NOx produced in the engine. That is even the case with 1980s Hondas. The hydrocarbon emissions also drop, and do so faster than the NOx. Which leaves unbalanced reactants for the cat to neutralize even the reduced NOx emissions.

    I'm guessing the injected hydrogen reacts with the excess oxygen in the cylinder before nitrogen does. Thus you get cylinder NOx levels low enough for the cat.

    Still isn't a large engine. Some pick ups here had engines with 1L cylinders.

    Go back far enough, and no car had emission controls, and the majority didn't care.;)

    Lean burn produces less NOx, but then the emission ratios are off for a three-way cat to clean up all the NOx that is made. It's why diesels need extra equipment to meet today's regulations.
     
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  9. austingreen

    austingreen Senior Member

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    First two generations of the civic which went to the early 1980s didn't have cats except a 2 way in the larger 1.5L engine and that bigger 2nd gen engine couldn't be sold in California. By the third generation regulations got rougher and they had 3 way cats. the 3 way cat can't provide reduction of NOx in a lean burn well because there is too much oxygen in the exhaust. A trap or SCR is needed, and if using a trap then periodically you need to provide fuel (sometimes from rich mixtures, sometime directly) to reduce NOx to N2 to clean the trap.

    I am not sure since that lexus has a racing engine and they don't provide specification. The only tji engine to make it to a production car is the phev - amg one, and they had to do some serious work on the f1 engine to meet emissions. That is rumored to go up to lambda 1.3. They use 16 KW from the battery to heat the 3 way catalytic converter and likely have a trap in it that they occasionally need to run rich mixtures to clean. My guess is Toyota must be working on the catalyst side, and its possible to have a NOx trap that will absorb in cold or lean conditions, then reduce when temperatures and a rich mix meet it. Toyota may have worked on NOx traps/regeneration for their hydrogen and diesel engines.

    I have no idea why toyota wants a lambda of 2.5. In a naturally asperated engine going that low would likely hurt instead of help efficiency. I would expect whatever they produce will be fairly low on NOx, but would still need something to reduce it to meet emissions. We will need to wait at lease a couple of years to see if they are really going to put that part in a production car. Going that lean in a turbo charged car when less power is needed makes some sense as some of the energy of pumping the extra air is recovered. In naturally aspirated I would think atkinson valving and using cooled egr like the current prius for that condition would be the most efficient.
     
  10. austingreen

    austingreen Senior Member

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    The excess oxygen means a normal cat won't work. Some of the hydrogen will react with the oxygen but its part of the fuel so should be included in the calculation of lambda. The hydrogen reduces with NOx in these reaction

    4NO + H2 -> 2N2 +2H2O, 2NO2 +H2 -> N2 +2H2O.

    The water vapor produced also cools the cylinder. A water + methanol injection will also do this work. Hydrogen or rich mixtures can also clean a NOx trap and this would require less hydrogen than hydrogen injection to reduce the same amount of NOx.
     
  11. Gokhan

    Gokhan Senior Member

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    Again, no. They are studying much more lean burn. Again, it has nothing to do with hydrogen. Again, emission regulations of 2030 are not the same as that of 2000.
     
  12. Trollbait

    Trollbait It's a D&D thing

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    The paper you posted.
    FlexPaper AdaptiveUI JSP Example

    They targeted a NOx emission limit of 0.1g/kWh. The only engine to reach that limit was using hydrogen addition. They show the test engine getting lower NOx with the directed 2 hole injector vs a homogeneous mixture, but the presented data units does not allow comparison to the 0.1g.kWH target. NOx discussion ends with "The results of combustion properties and low NOx will be described later." Is that in a section cut off for the preview copy, or another paper?
     
  13. Isaac Zachary

    Isaac Zachary Senior Member

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    I have no idea what lambda number is stoichiometric or what 2.5 means (lean or rich???, I understand AFRs although I suppose there's a reason we're talking lambda here.) At any rate, yes, a "perfect" engine (in terms of efficiency) would cram as much oxygen in a cylinder and perfectly mix it with a perfectly stoichiometric mix of fuel and run that at as full throttle as possible in as high of a comrpession ratio as possible. Obviously a perfect engine is impossible.

    Leaning out the fuel mix can get more to burn during the combustion cycle, since it's virtually impossible to mix the air and fuel well enough to create a perfectly homogenous mix. So the result in a stoichiometric mix is you get some rich pockets that don't burn until the hit the catalytic converter (and you also get some because the flame quenches before reaching the edges of the combustion chamber leaving a layer of unburnt air and fuel along the surface of piston top and combustion chamber.

    Leaning out also does the same as the EGR valve, it makes the engine produce less power so you can open up the throttle more, so less pumping losses.

    But in the end, lean burn is also cooler, and the greater the heat difference the more efficient.
     
  14. Gokhan

    Gokhan Senior Member

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    Hydrogen is not studied or used or proposed to be used in this all-new engine in this Toyota paper—period.

    The fuel mixed with hydrogen was used in a conventional engine to study lean mixtures in a conventional engine, as regular fuel wouldn't burn in a conventional engine if the mixture was too lean. The all-new engine uses regular fuel, but they also say that they can use gasoline containing ethanol to further increase the thermal efficiency.

    The abstract summarizes it all:

    It is well known that lean burn is an effective technology to increase thermal efficiency of engine highly. However, since NOₓ emission from lean-burn engine cannot be reduced with three-way catalyst, there have been issues such as complicated system configuration due to the addition of NOₓ reduction catalyst or limiting lean operation to narrow engine speed and load in order to meet emission regulation of each country. This paper introduces super-lean-burn engine with over a stoichiometric ratio λ = 2.5 that achieves both high thermal efficiency and significantly low NOₓ emission in order to solve the issues of conventional lean-burn engine. Key technologies for combustion such as ignition, flame propagation, and unburned HC reduction are described firstly, and then the possibility of further improvement of thermal efficiency and combustion effect by applying ethanol as CN (Carbon neural) fuel to the super-lean-burn engine is indicated.

    This engine is not really a stratified-mixture engine like the Honda engines of the 1980s-1990s. They do use a rich mixture at the plug to achieve ignition, but they then try to make a homogenous mixture. Turbulence and fast flame propagation are among key innovations.
     
  15. Trollbait

    Trollbait It's a D&D thing

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    But the paper only shows it is leaner in comparison to the lean engine using a homogeneous charge.
    Then the NOx being lower does not answer the question of whether a car using it needs additional emission controls beyond the standard three-way cat?
     
  16. Gokhan

    Gokhan Senior Member

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    It does not.

    On page 2, under super-lean-burn concept, they say that they achieved high thermal efficiency and low NOₓ that met the emissions standards without using an NOₓ-reduction catalyst.
     
  17. Trollbait

    Trollbait It's a D&D thing

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    They set that as the challenge there. While they show lowering NOx emissions being produced by the engine, they did not show those emissions being low enough to meet regulations without additional exhaust controls.

    Leaning out the fuel mixture has always lowered the NOx produced by the engine. The unburned oxygen in the exhaust interferes with a 3-way cat's ability to reduce the NOx. Less is made in the engine, but more comes out the tailpipe.
     
  18. Gokhan

    Gokhan Senior Member

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    Ha, if you are a Toyota naysayer, sure. Nevertheless, I read it as they have achieved it. Now, exactly how much the thermal efficiency will be remains to be seen.
     
    #138 Gokhan, Jun 14, 2024
    Last edited: Jun 14, 2024
  19. Trollbait

    Trollbait It's a D&D thing

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    It isn't about Toyota.
     
  20. Andy Pants

    Andy Pants New Member

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    So let me get this straight, they are making the already "too small for Americans" Prius even smaller?! Wth are they thinking??? The gen 5 Prius is already completely useless due to it's size, will gen 6 just be a two seater for people under 5'3"?!
     
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