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Prius Thermal Thresholds

Discussion in 'Gen 2 Prius Technical Discussion' started by Dan., Mar 28, 2007.

  1. Dan.

    Dan. MPG Centurion

    Joined:
    Sep 7, 2005
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    Location:
    Houston, Texas
    Vehicle:
    2007 Prius
    Disclaimer: I'm a Fuel Efficiency phreak. I do unusual things to save gas.

    I've been reading on thermal mods the the Prius and I've read the articles on the Prius Stages. What I gathered is that stage transitions begin around 45c and complete around 85c.

    So I deduced that the best (efficient) temperature to operate the Prius at is 85c (or possibly above).

    Does anyone know what temperature is too hot? 110c, 120c, 130c, 140c? I just got the ScanGuage II so I'll have hard numbers next month.

    Since my morning commute rarely lands me in S4, I think that my block temp is a slow progression from 20c to 80c. With a block heater, It should move up to 40c to 100c. With grill blocks possible 40c to 140c.

    So when does heat hurt and not help efficiency? What temp is too hot? What temp turns on the idiot light for overheat?

    I know it seems absolutely insane to do this in Texas, but please refer to my disclaimer.

    PS. Prius refers to '07 Prius II

    11011011
     
    #1 Dan., Mar 28, 2007
  2. tochatihu

    tochatihu Senior Member

    Joined:
    Apr 10, 2004
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    Location:
    Kunming Yunnan China
    Vehicle:
    2001 Prius
    I suppose that all the good mpg stuff happens when your ICE coolant is above 85 oC. You would have to do a lot of 'thermal management' to get it above 100 oC. Prius is pretty darn good at shedding engine heat.

    Anyway, if you can manage to exceed 100 oC, you are beginning to pressurize the rubber tubing that runs the coolant here and there. It is not to your advantage to do that.

    The electrical fans will begin to spin and draw a hundred watts (or two) when that coolant gets above 95 oC or so. You don't want to throw that away, so plan to live your efficient life between 85 and 95.

    It ain't hard.

    I am not sure whe know what it takes to make the hot coolant light come. I've not seen it, nor have I heard it reported by others. Our best hope is that it would appear before the rubber tubing fittings detach.

    PS: if you are a phreak, check in at www.cleanmpg.com
     
    #2 tochatihu, Mar 28, 2007
    1 person likes this.
  3. ken1784

    ken1784 SuperMID designer

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    Dec 18, 2003
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    Location:
    Yokohama, JAPAN
    Vehicle:
    2010 Prius
    Model:
    N/A
    Japanese Prius Tech Manual says the thermostat specification is starting to open at 82C and fully open at 95C.
    Cooling fans starts at 96C.
    We see the typical coolant temperature is about 88C.

    Ken@Japan
     
    #3 ken1784, Mar 28, 2007
    1 person likes this.
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