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Question about "fooling" the temp guage on an 06 prius

Discussion in 'Gen 2 Prius Technical Discussion' started by satsuke, Apr 11, 2008.

  1. satsuke

    satsuke Junior Member

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    I remember from a japanese news video of some of the hypermiler clubs using a technique that amounted to feeding the warmed-up temperature directly into the onboard computers instead of letting it decide when to spin up the ICE to maintain optimal emissions and such.

    Has anyone stateside done this, and are the sensor points somewhere where one might access them without ripping the car apart?
     
    #1 satsuke, Apr 11, 2008
  2. ForTheGlory

    ForTheGlory New Member

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    Probably won't hurt anything, but here are my two standard caveats:

    -The Prius works the way it does for a reason. Any effort to try to "trick it" may carry unintended consequences.
    -Not sure on the legality of doing this. While the Prius would have pretty low emissions even with a cold cat, you are trying to intentionally bypass an emission control device. Being that most states require emissions inspections, it's probably not legal to do that.
     
    #2 ForTheGlory, Apr 11, 2008
  3. satsuke

    satsuke Junior Member

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    Kansas doesn't do any inspections unless you retitle it from out of state .. and even than they only look at if the VIN #s match everywhere and if the color and options and such match whatever documentation they have on it.

    At least such a mod wouldn't be as extreme as some people I've met that have removed the cat entirely and made it a straight pipe .. with the lack of inspections here and the rash of converter thefts ,. this might be becoming more common, though I'd hate to think what it'd do to onboard computers on any car to have the exhaust pressure removed.

    /me still remembers my first hyper econo-car ,. 1979 datsun b210 .. ~34mpg and leaded gas .. econo in that it costs $3500 new and had heat ,. and that was it.
     
    #3 satsuke, Apr 11, 2008
  4. miscrms

    miscrms Plug Envious Member

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    I do believe this would be violation of federal law, regardless of what state you are in.

    Rob
     
    #4 miscrms, Apr 11, 2008
  5. ken1784

    ken1784 SuperMID designer

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    #5 ken1784, Apr 12, 2008
  6. racerbob

    racerbob Member

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    You could get a MIL illumination from that hack. Most vehicles today will run plausibility checks on important sensors by comparing them to another (intake air temp) on cold startup. If they are not similar in resistance, a fault will be stored. The CCM (part of the OBD 2 specification for all automakers) constantly monitors this circuit for high/low and short circuits. Turning a pot too fast would be a situation that the ECM could flag as a fault. Resulting lean condition on a cold engine when it goes into closed loop (early) will most likely set a lean code when O2 monitoring begins. Remember that an internal timer is also used to countdown the proper time to closed loop based on the startup coolant temp. The software is quite sophisticated and not very easilly fooled.
     
    #6 racerbob, Apr 12, 2008
  7. Bob64

    Bob64 Sapphire of the Blue Sky

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    short answer: dont use the hack unless your using the EBH.
     
    #7 Bob64, Apr 14, 2008
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