Direct Injection or Fuel Injection?

Discussion in 'Gen 4 Prius Technical Discussion' started by Elt31987, Sep 13, 2016.

  1. Elt31987

    Elt31987 Active Member

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    Does anyone know if the 2016/7 Prius uses DI and FI?
     
  2. alanclarkeau

    alanclarkeau Senior Member

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    I would suspect Fuel Injection - I'm still thinking about whether Direct Injection would be any advantage (or even possible??) with an Atkinson Cycle engine?
     
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  3. JDenyer232

    JDenyer232 Member

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    It'sregular multi-port fuel injection. While direct injection can be used in Atkinson cycle engines, i think Toyota didn't use it due to frequent stop starts of the gas engine. This could lead to intake port and valve deposits, as well as emission issues. Direct inject engines tend to produce lots of particulate matter in the form of soot. Hope this helps.
     
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  4. Elt31987

    Elt31987 Active Member

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    Appreciated!
     
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  5. MikeDee

    MikeDee Senior Member

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    Lexus has it. Hyundai Iconiq has it.
     
  6. PRPrius

    PRPrius Active Member

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    Toyota uses multi-port fuel injection on the Prius. However, Toyota doesn't use Direct Injection only engines on any of their vehicles including Lexus. They use a system call D4-S which is a hybrid Port and Direct injection. A normal 6 cylinder engine like the one found in the revised 2017 Toyota Sienna would have 12 injector instead of the 6 found on the 2016 engine. 6 injectors would be low pressure port injector used during initial start-up and under low load conditions. The high pressure injectors are used under normal idle, low load and high load conditions. Under high load conditions only the direct injectors are used in order to cool the intake charge in the combustion chamber. Subaru uses the D4-S system in the engine found on the Subary BRZ/Toyota GT86 formerly Scion FRZ. This system has the added benefit of reducing carbon build up on the back of the intake valves since gasoline still passes through them when the low pressure injectors are in use.
     
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  7. MikeDee

    MikeDee Senior Member

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    An Atkinson engine pushes the fuel/air mixture up past the intake valve into the intake manifold, so doesn't it inherently prevents carbon buildup on the backside of the intake valve?
     
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  8. Trollbait

    Trollbait It's a D&D thing

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    In theory it could, but it could also wait until the intake valves close before injecting fuel.

    Earlier direct injection engines had build up issues, but control of injector pulse timing should reduce them. The real plus of port/direct injection is reduced particulates. When enforced, EU regulations would require DI to have exhaust filters like diesels. Some port injected engines have exceeded the particulate limits in the past.
     
  9. eric1234

    eric1234 Active Member

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    My understanding is that the build up occurs on the backside of intake valves as a result of "dirty" (oil vapor rich) air resulting from PCV. Because there is no gasoline to clean up the valves. Not sure how injector pulse timing would reduce such deposits??
     
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  10. Trollbait

    Trollbait It's a D&D thing

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    Early DI designs had serious deposits. Now they don't. It could be that the PCV system is better at reclaiming oil vapor for the crankcase, or just not letting as much out.

    Guess I'll put an oil catch can on any non turbo DI get though. I've put such of port injected cars in the past, and they do catch a lot of oil.
     
  11. bhtooefr

    bhtooefr Senior Member

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    Another thing that Mazda does is try to get the intake valves as hot as possible to burn off the deposits.
     
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  12. eric1234

    eric1234 Active Member

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    How do they do that? Usually higher temperature(s) accelerates the coking of petroleum distillates...
     
  13. bhtooefr

    bhtooefr Senior Member

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  14. eric1234

    eric1234 Active Member

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  15. MikeDee

    MikeDee Senior Member

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  16. RCO

    RCO Senior Member

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    The expression 'high' is entirely relative. You need a baseline for it to have any real meaning.
     
  17. MikeDee

    MikeDee Senior Member

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  18. jdenenberg

    jdenenberg EE Professor

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    Perhaps when we develop something better that satisfies most needs. EVs, Fuel Cells, and others are not quite there yet for most families.

    JeffD
     
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  19. alanclarkeau

    alanclarkeau Senior Member

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    TOYOTA have said that the new C-HR 1.2 litre Turbo has Direct Injection - with variable valve timing which has "the ability to switch to the fuel-saving Atkinson cycle". I'm not sure if this has any similarity to the valve timing arrangement on PRIUS, or something totally new.

    < New C-HR engine offers more for less >

    But it's still got pistons.
     
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  20. bhtooefr

    bhtooefr Senior Member

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    So, what the 8NR-FTS has is wide-authority variable valve timing. Basically, at times of light load, it retards the intake camshaft (makes it open and close later than normal) to push excess air back out of the cylinder into the intake manifold.

    The Prius's engine does the same thing, except it does it all the time, not just at light load.
     
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