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Variable back pressure exhaust

Discussion in 'Gen 3 Prius Main Forum' started by HTMLSpinnr, Apr 30, 2009.

  1. HTMLSpinnr

    HTMLSpinnr Super Moderator
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    Just one more way the new 2010 Prius improves on efficiency... the new 2010 Prius muffler has a spring loaded bypass valve to improve performance at various speeds.

    For low power operation, the valve flap remains closed guiding exhaust gases through an additional chamber for quieter operation. However, during mid to higher power (flow) operation, the valve progressively opens to bypass one of the chambers for substantially lower back pressure and improved performance.


    [​IMG]


    *1 - Exhaust Gas
    *2 - Control Valve Closed
    *3 - Control Valve Open
    *4 - Low Engine Speed
    *5 - Middle to High Engine Speed

    Yet another tidbit from the 2010 NCF Guide.
     

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    #1 HTMLSpinnr, Apr 30, 2009
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  2. efusco

    efusco Moderator Emeritus
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    Wow! very elegant.
     
    #2 efusco, Apr 30, 2009
  3. cwerdna

    cwerdna Senior Member

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    Interesting... My former 2002 Nissan Maxima had something like that as well. Looking at some FAQs, it looks like they started doing that in the 2000 model year.
     
    #3 cwerdna, May 1, 2009
  4. bedrock8x

    bedrock8x Senior Member

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    This exhaust system already used in the Camry Hybrid since 07.
    This is another improvement carried over from the TCH and so is the PSD.

     
    #4 bedrock8x, May 1, 2009
  5. PriusLewis

    PriusLewis Management Scientist

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    The one in the Corvette is a costly option, has servos and is controlled by the computer. Prius uses a spring to accomplish the same thing. Way to go, Toyota!

    Now to figure out how to put a cable on it to make it louder when cruising through the local Sonic :scared:
     
    #5 PriusLewis, May 1, 2009
  6. EZW1

    EZW1 Active Member

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    I concur: way to go Toyota!

    But I have one reservation: Inside the muffler this spring will be exposed to many harsh enivornments:
    a. High temps
    b. Water (byproduct of combustion and often seen dripping from a tailpipe until the exhause system is hot enough to turn it into steam)
    c. Water vapor
    d. Combustion byproducts like sulfur, and other chemical compounds
    e. Hydrocarbons that are not burned in the CAT

    All of these will lead to a spring failure. Now the real question is: will the spring last the life of the muffler or die sooner?
     
    #6 EZW1, May 1, 2009
  7. Paradox

    Paradox Prius Enthusiast / Moderator
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    I am sure this wouldn't matter at all but would it have made a little more sense for the 'hinge' on the valve to be on the other side? Then the exhaust gas would have been guided in the proper direction. Also, the exhaust going around the other way would not hit the 'partial roadblock' created by the valve as shown in the diagram.
     
    #7 Paradox, May 1, 2009
  8. PriusLewis

    PriusLewis Management Scientist

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    Around 1970 Pontiac offered a vacuum-powered manually controlled variable exhaust on the GTO. This is a very rare and little known option (search Youtube for GTO superbowl commercial - I can't here at work or I'd provide a link- it was advertised exactly once). The control system outlived the mufflers, and this was back in the days of no cats and leaded fuel (which was much dirtier on the muffler internals).
     
    #8 PriusLewis, May 1, 2009
  9. HTMLSpinnr

    HTMLSpinnr Super Moderator
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    Keep in mind the muffler is a cylindrical chamber, and this pipe and valve assembly is likely in the center.
     
    #9 HTMLSpinnr, May 1, 2009
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