Did 4th Gen fix 3rd Gen?

Discussion in 'Gen 4 Prius Main Forum' started by AC / DC, Jun 17, 2021.

  1. AC / DC

    AC / DC New Member

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    Hi Everyone! -- I am a gearhead but new to hybrids. I am planning on buying my first hybrid and was thinking buying a Gen3 would be good, but after posting in that 3rd Gen group, reviewing the replies, and researching available data regarding the EGR/OIL/Piston Rings/Head Gasket Failures; I decided to go for a 4th generation.
    Could you guys please help me understand how Toyota addressed those issues in the 4th Gen?

    I appreciate your help!

    Thank you,
     
  2. amos

    amos Active Member

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    Smart choose 4th is much better in many aspects. Not recommending a gen 3 . not reliable for high milage commutes.
     
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  3. bisco

    bisco cookie crumbler

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    i'm not sure gen 4 is out of the woods yet, since it is still mostly older gen 3's having the problems, but as i understand it, they have redesigned the egr, and probably improved the pistons and rings.

    time will tell. i would give it a few more years, maybe 2024

    but for a gear head, what's a head gasket or salvage engine? fun!
     
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  4. AC / DC

    AC / DC New Member

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    [QUOTE="
    but for a gear head, what's a head gasket or salvage engine? fun![/QUOTE]

    I am leaning towards the Prius because I need a daily driver that requires low maintenance. I have a BMW 335 twin turbo that my wife and I enjoy immensely. It keeps me quite busy wrenching and I enjoy that a lot. Not need to add another needy car to my tight weekends ☺️
     
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  5. bisco

    bisco cookie crumbler

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    what's your budget?
     
  6. AC / DC

    AC / DC New Member

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    $22k. I am in MN though.
     
  7. bisco

    bisco cookie crumbler

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    not worth traveling?
     
  8. AC / DC

    AC / DC New Member

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    Not really, but thank you.
     
    #8 AC / DC, Jun 17, 2021
    Last edited: Jun 17, 2021
  9. rjparker

    rjparker Senior Member

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    The piston and piston ring problems were resolved in mid 2014 gen3s. By 2016 Prius had the new global architecture which includes better rear suspension, new large volume egr design, new cylinder cooling strategies, active grill shutters, new intake, new inverter, new transaxle, new hv battery design, better mpg and more.

    Partial from
    4th-Generation Toyota Prius Teardown (Part 1) - MarkLines Automotive Industry Portal

    Stronger airflow in combustion chambers
    [​IMG]
    The re-designed intake port shape (Source: Toyota)
    The first improvement was changing the shape of the intake port based on an analysis of the "tumble flow," which is the vertical swirl of air-fuel mixture entering the combustion chamber. As illustrated in the image on the right, (1) the airflow was made straight and, (2) the inverse tumble component that blocks the tumble flow was reduced. As a result, the tumble ratio was improved from 0.8 to 2.8, the combustion velocity increased, and induction of a large volume of EGR (exhaust gas recirculation) gas became possible.

    The shapes of the combustion chamber and the piston-top surfaces account for the tumble flow described above.

    Large-volume cooled EGR
    The EGR distribution passage in the intake manifold has been restructured to a tournament design. This allows a larger amount of EGR gas to enter evenly into each cylinder.

    [​IMG]
    The intake manifold cross-section (Source: Toyota) [​IMG]
    The aluminum pipe at the left connects to the EGR passage


    [​IMG]
    An external view of the intake manifold [​IMG]

    The throttle valve (center)
    The intake manifold that directs air into the intake port is shaped so that it branches into two passages from the throttle valve, and supplies intake air into the respective ports after converging once at the collector located immediately before the cylinder head. This design ensures a smooth flow of intake air by increasing the cross-sectional area that the incoming air passes through, which minimizes air resistance and interference between cylinders.



    [​IMG]
    The EGR cooler configured at the back of the engine [​IMG]
    The EGR cooler unit


    A newly-designed water jacket spacer optimizes cylinder bore wall temperature
    [​IMG]

    The structure of the water jacket spacer (Source: Toyota)
    In order to achieve optimized cooling by means of the cylinder bore region, a water jacket spacer consisting of stainless steel and foam rubber has been adopted. This involves a foam rubber with a brand name of EXPAD being placed in the coolant passage at the bottom of the cylinder bore. This allows a large amount of coolant to flow over the upper part of the cylinder bore, which becomes very hot, and ameliorates knocking by raising the cooling effect. At the same time, allowing a smaller amount of coolant to flow to the lower half portion of the bore to maintain a high temperature. With these techniques, fuel efficiency is achieved by making the expansion factors of the upper and lower cylinder bore even, and piston action friction is standardized at a low level.

    Plus new inverter and hv battery design.
     
    #9 rjparker, Jun 17, 2021
    Last edited: Jun 17, 2021
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  10. alanclarkeau

    alanclarkeau Senior Member

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    The huge difference between the 2 - is how it drives. It's actually fun to drive, rather than just transport - and pretty ordinary at that.

    The engine is an evolution - with some big improvements in efficiency. Toyota don't release the details of the improvements, though, I suspect many/most parts are not interchangeable.

    Those problems you mention were fairly rare in Gen 3 - Gen 4, there have been almost no mention of problems, apart from one car with very high miles (200k+) which had worked hard in a short time.
     
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  11. Pv5

    Pv5 New Member

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    Thanks to rjparker for the above, very interesting and informative! I'm a fairly new owner of a 2013 v Five with less than 50K miles and thus far pleased with the car (first hybrid for me). My hopes are that the reliability and ownership/maintenance costs are high and low, respectively.
     
  12. AC / DC

    AC / DC New Member

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    RJParker, YOU ROCK! this data is just awesome! Thank you. I can clearly see and follow the system design. - It clear outs many questions I had.

    Alanclarkeau, Thank you. I will be testing some sometime in a week or so.

    Thank you to all,
     
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  13. Mendel Leisk

    Mendel Leisk Resonant Resident

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    I sort-of beg to differ; like the feel of our 2010. That said, it's the Canadian "Touring" model, came with 17" wheels, different steering and maybe some suspension tweaks.
     
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  14. ASRDogman

    ASRDogman Senior Member

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    My 2010 only has 239,300 miles. Head gasket fine, only use about 1.5 qts of oil every 10,000...
    No complaints! Average 48mpg's...

    Also: "This involves a foam rubber with a brand name of EXPAD being placed in the coolant passage at the bottom of the cylinder bore."
    mmmmm Gen3 had egr cooler blockage, Gen 4 has rubber coming apart in the engine...
    What could go wrong???


     
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  15. amos

    amos Active Member

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    Well well. What about that foam rubber inside the engine? Any more info about what its doing and what's it for? Why would it need to be replaced? Sounds like something that might develop to taking engine apart.
     
  16. ASRDogman

    ASRDogman Senior Member

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    From post #9:
    "In order to achieve optimized cooling by means of the cylinder bore region, a water jacket spacer consisting
    of stainless steel and foam rubber has been adopted."

    And a few other things... That "rubber" is going to be under constant heat. How long will it survive?
    If it starts to break down, how will it happen? Will it start breaking apart and blocking coolant passaged?
    will it deform, also blocking coolant flow? Maybe only Toyota knows.
    How long before it starts to become a problem like the Gen3 head gasket failure because the EGR Cooler gets
    clogged?

    I am not saying it will, but it seems like a weak point of the block.
     
  17. Rmay635703

    Rmay635703 Senior Member

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    Brand new prime $19,500 sounds like the best option