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Hydrocarbon Converter - HC Valve

Discussion in 'Generation 1 Prius Discussion' started by bwilson4web, May 17, 2013.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    In practice, the HC valve closes during the early cold start before the catalytic converter starts working. A catalytic converter has to get very hot before it can reduce the hydrocarbons and NOx. So this valve closes during the early startup that forces the early, rich mixture exhaust to take a path that 'holds the startup hydrocarbons.'

    [​IMG]
    "Development of the Hybrid Vehicle and its Future Expectation" Shinichi Abe, SAE 2000-01-C042, October 16-18, 1999

    My studies indicate the engine runs 45-55 seconds in 'closed loop' mode while the catalytic converter heats up. During this time, a computer controlled, vacuum valve is set so the spring and piston closes the HC valve forcing the exhaust through a path that is supposed to trap the soot and hydrocarbon rich, starting exhaust. If more engine power is needed during this time, the valve opens. But the historical problem as been linkage corrosion of the HC valve.

    My understanding is the linkage corrosion occurs most frequently in areas that salt their roads. Certainly WD-40 would be an option. Others have used lithium grease.

    Now I've seen (owned cars) that injected air into the exhaust. But I remember they had a belt driven, air pump that created the higher pressure needed to overcome the exhaust pressure. I have not found a similar air pump in our NHW11. It would also need plumbing to get the high pressure air to the exhaust.

    Bob Wilson
     
    #1 bwilson4web, May 17, 2013
  2. ChapmanF

    ChapmanF Senior Member

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    Soon after buying mine, I worked in antiseize lubricant around that shaft - the same silvery stuff you use on bolts you don't want to get stubborn (and then spend half an hour trying to clean off hands and clothes). One of the material properties often mentioned for this stuff is high temperature resistance. Don't know if it's any better for the purpose than WD40 or lithium grease, but it has done the trick for me these five years.

    -Chap
     
    #2 ChapmanF, May 18, 2013
  3. lueung

    lueung Junior Member

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    Bob.

    Thank you for the detailed explanation. I am learning quite a bit about the Prius since getting it. Perhaps you can take a look at another issue I am trying to track down: 2001 Prius: p0440, p0441, p0446 | PriusChat

    Without having a working Prius to compare it, it is hard to know what is the norm and what is not.
     
    #3 lueung, Jun 27, 2013
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