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Variable exhaust valve

Discussion in 'Gen 3 Prius Technical Discussion' started by Mrpcar, Feb 16, 2013.

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  1. Mrpcar

    Mrpcar Active Member

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    While wrenching on the Prius today I notice something interesting. These adjustable valve for the exhaust system is quite common on most of the European cars I own. they serve 2 purposes (1). Keep back pressure for low end torque (2). Meet strict drive by noise pollution standard (in Europe)

    But I was surprised to find this on the Prius. Can anyone tell me what's it is used for?

    [​IMG]
     
    #1 Mrpcar, Feb 16, 2013
  2. El Dobro

    El Dobro A Member

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    Can't exactly tell where it is in relationship to everything else. Maybe the EGR valve?
     
    #2 El Dobro, Feb 17, 2013
  3. Mrpcar

    Mrpcar Active Member

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    I am very positive it is a valve that controls the flow of the exhaust, definitely used to control back pressure.
     
    #3 Mrpcar, Feb 17, 2013
  4. prj

    prj Member

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    It's the exhaust heat recovery system. Coolant is circulated around the exhaust pipe to help the engine warm up faster.

    See the photos in this thread.

    [​IMG]
     
    #4 prj, Feb 17, 2013
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  5. Mrpcar

    Mrpcar Active Member

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    But I noticed an actuator looking device that goes to the exhaust, didn't look like a coolant circulating pipe. In addition there were no return line back to the engine. Does the 2013 model still have the coolant recirculating device?
     
    #5 Mrpcar, Feb 17, 2013
  6. bisco

    bisco cookie crumbler

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    probably. it's fairly new, replacing the old storage cannister.
     
    #6 bisco, Feb 17, 2013
  7. bisco

    bisco cookie crumbler

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    perhaps both lines are in that lower silver pipe.
     
    #7 bisco, Feb 17, 2013
  8. David Beale

    David Beale Senior Member

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    The second pipe is under the exhaust exit in the photo. It's the exhaust heat recovery module.
     
    #8 David Beale, Feb 17, 2013
  9. El Dobro

    El Dobro A Member

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    Here's a walkaround of the pipes in the pic.
     
    #9 El Dobro, Feb 17, 2013
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  10. bwilson4web

    bwilson4web BMW i3 and Model 3

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    When next you get under the car, you can find in sequence:
    1. The exhaust recirculation pipe is part of the exhaust manifold before the catalytic converter and feeds into a coolant operated, heat exchanger. This remains an area of some interest because of the legacy systems in the 1970s that often froze up from exhaust coke in the bad old days of carburetors. [​IMG]
    2. As others pointed out, your photo shows the coolant heater that uses hot exhaust gas downstream of the catalytic converter when the engine is too cool. [​IMG]
    3. At the end, the muffler has a by-pass valve that opens at high gas-flow rates, possibly requires higher speeds too. I've only seen it in the shop manual.
    Bob Wilson
     
    #10 bwilson4web, Feb 17, 2013
  11. Mrpcar

    Mrpcar Active Member

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    Ah! So there is a variable exhaust valve! Thank you for the explanation. I've seen various these type of variable valves on a lot of European cars. I've seen them as early as 1997 BMW 3 series. The valve is kept close from idle until after 3k rpm, purpose was to keep the back pressure for better low end torque. This was an interesting inexpensive design prior to the variable valve timing days.
    Then I saw these valves on both newer Porsches and Ferraris, the purpose now is different due to strict European noise pollution. Ferrari actually had an interesting approach to keep their car still sounding somewhat a Ferrari and yet meet the regulation. The valve is defaulted on an open position when the car is stopped. As soon as the engine starts the engine vacuum will close the valve. So this to makes the car sound good on start and then quiet down right away. The valve opens again on higher rpm and speed.
     
    #11 Mrpcar, Feb 17, 2013
  12. OceanEyes

    OceanEyes Active Member

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    Interesting to see the "nuts and bolts" of the drive train... have to show this to my brother who rebuilt his '78 Rally Sport Camaro three times and is babying a '67 Super Sport... this drive train looks "elegantly" simple to this newbie compared to buckets of bolts and parts lying on a garage floor. ;)
     
    #12 OceanEyes, Feb 17, 2013
  13. RRxing

    RRxing Senior Member

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    Here's the meat and potatoes...
     

    Attached Files:

    #13 RRxing, Feb 17, 2013
  14. Mrpcar

    Mrpcar Active Member

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    Thanks, very interesting to find this technology in a car of this price range. Way to go Toyota!!!! Now if they can just beef up their sheet metal and up one size on all of their bolts then they would be the king! :)
     
    #14 Mrpcar, Feb 17, 2013
  15. bisco

    bisco cookie crumbler

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    and put in a more comfy driver seat and better handling on the highway. ah shoot, i should'ev just bought a bmw.
     
    #15 bisco, Feb 17, 2013
  16. Mrpcar

    Mrpcar Active Member

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    Germans makes some pretty amazing machinery. I can't help say this whenever I work on a German car. "Those crafty little Germans! They are the best blacksmith!"
     
    #16 Mrpcar, Feb 17, 2013
  17. El Dobro

    El Dobro A Member

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    Is this from a Prius manual?
     
    #17 El Dobro, Feb 17, 2013
  18. RRxing

    RRxing Senior Member

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    2010 Prius New Car Features. I downloaded it along with a host of other things from the Toyota Technical Information System (TIS.) Was $15 for two days access back in 2009. Here's the link...

    https://techinfo.toyota.com/
     
    #18 RRxing, Feb 17, 2013
  19. El Dobro

    El Dobro A Member

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    Ok. I'm trying to figure out exactly where the valve is. Your attachment says it's in the main muffler, so where is the main muffler? The parts book calls it the piece at the end of the car, so if that's it, it's not what the OP is looking at.
     
    #19 El Dobro, Feb 17, 2013
  20. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Perhaps this helps:
    [​IMG]
    Source: 2010-Prius-NCF-Engine-Exhaust-Details.pdf

    Bob Wilson
     
    #20 bwilson4web, Feb 17, 2013
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