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NHW20 CHS thermos into an NHW11?

Discussion in 'Gen 2 Prius Technical Discussion' started by ChapmanF, Mar 30, 2008.

  1. ChapmanF

    ChapmanF Senior Member

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    Has anybody tried to fit a thermos from an NHW20 into an NHW11?

    With the number of short trips I have to make (several hours apart),
    it's hard for me to get out of the 35-40 mpg club. I'm sure an EBH
    would make a big improvement, and I mean to add one ... but I
    strongly suspect a thermos would make an improvement too, and
    with less day-to-day inconvenience.

    I'm guessing problem #1 might just be finding any space at all to
    hang the silly thing. I'm sure the ECU won't have any firmware
    support for running the pump at shutdown and prestart, but I
    wonder how bad it would be to just have the thermos in the
    heater-core circuit at all times and omit the pump. There would be
    hot coolant in it at shutdown anyway, and it wouldn't be prepumped
    into the ICE at startup, but it would be in circulation right away,
    which sounds almost as good. Maybe I could work in a valve to
    isolate the thermos with IG off, just to prevent any convective
    circulation overnight.

    What do you think? Could it be workable? Has anybody done it?

    Can somebody NHW20-savvy describe in more detail exactly how
    it works there? I am assuming the system is filled with a coolant
    volume that fills the ICE and thermos at all times - that is, the
    pump at coolant storage or preheat time isn't actually emptying
    either space to fill the other, but just circulating hot stuff to where
    the cool stuff is and vice versa. RIght?

    Thanks for any ideas,
    -Chap
     
    #1 ChapmanF, Mar 30, 2008
  2. statultra

    statultra uber-Senior Member

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    i believe you have some space to mount it, where the air intake resonator is, on the passenger side behind the bumper.
    you would of course need to remove the resonator.
    theres a 3 way valve, that you would need.

    take a look here too

    Auto Parts People

    [​IMG]
     
    #2 statultra, Mar 30, 2008
  3. efusco

    efusco Moderator Emeritus
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    I'm pretty sure you'd be the first to do this!
    I think I'd try to build my own custom thermos and fit it in a convenient space. And then use a manually activated pump of some sort that you could actuate upon start up and shut down.
    If you're building this from scratch you may as well build a little heater into the thermos to keep the fluid hot...you could wire it to the same plug as the EBH. If the thermos is well insulated it would probably take very little to keep the coolant hot within the thermos.
     
    #3 efusco, Mar 30, 2008
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Chap,

    I question your premise that the engine coolant heat recovery system will improve mpg noticeably. If it would make a difference, that difference should be noticeable in the first five-minute mpg bar. Having owned a 2001 as well as a 2004, my experience is that in both cases the first five-minute mpg shows ~25 mpg.

    The primary purpose of the engine coolant heat recovery system is to improve emissions during warmup and help NHW20 qualify for AT-PZEV status. The system is not installed in NHW20 Prius outside of North America.
     
    #4 Patrick Wong, Mar 30, 2008
  5. statultra

    statultra uber-Senior Member

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    you can wire it up to the inverter water pump,

    the hard part is figureing out how to wire the valve.
     
    #5 statultra, Mar 30, 2008
  6. ChapmanF

    ChapmanF Senior Member

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    What a great link! That's a keeper. Thanks. -Chap
     
    #6 ChapmanF, Apr 1, 2008
  7. ChapmanF

    ChapmanF Senior Member

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    Hmm, that is disappointing ... I had read about some significant first-five-minute improvements using the EBH, and it just seemed so much more appealing to just save the heat instead of making it again.

    I suppose I should have back-of-the-enveloped it...

    3 liters of water (6.6 lb) 100 degF above ambient
    -> maybe 660 BTU or 0.7 MJ
    (I'm probably leaving out some factor < 1.0 from irreversibility, never actually took thermo.)

    2 hours on 400W EBH -> 800 Wh or 2.9 MJ

    Well, maybe the thermos could be as good as half an hour or less of EBH, if it's chilly out and the thermos contents are 100 F higher. Hmmm....

    Thanks for the reality check.

    -Chap
     
    #7 ChapmanF, Apr 1, 2008
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