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Will the car "cool down" in a 5 min stop at home?

Discussion in 'Gen 2 Prius Fuel Economy' started by driving-mr-mel, Aug 24, 2010.

  1. driving-mr-mel

    driving-mr-mel Junior Member

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    Just brought home my 2008 Prius, and have been reading through threads. I've read that short trips = less mpg due to the warming up of the car. My question is, how long does it need to be off before it cools down. I have a 15 minutes commute home after work, but I stop at home for about 5 minutes, grab the dog, and head out again, for a 20 minute trip to my horses. Is that 5 minute stop short enough that when I head out the car isn't "cold" again? What's the max time I can leave the car off before I am back at square one? Thanks!
     
  2. hyo silver

    hyo silver Awaaaaay

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    I'd guess it would cool down some, but not completely. If you have to stop, then stop, and don't worry that you're ruining your mileage. You could always call on your way home and tell the dog to be ready when you get there. ;)
     
  3. uart

    uart Senior Member

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    Of course it will cool a little but not enough to really hurt efficiency in any big way. I'd say it will be back up to an efficient running temperature within about the first minute of that 20 minute trip. I find I've got to be stopped for a couple of hours before I'm really back to "square one".
     
  4. ksstathead

    ksstathead Active Member

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    Until the 2010, the problem with short stops is that a new warm up cycle is required even though the cool down in 5 minutes is nominal. If you can shut down stereo and climate control, etc. and leave in ready mode for the 5 minutes you avoid the forced engine on time.
     
  5. driving-mr-mel

    driving-mr-mel Junior Member

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    Thanks, as a newbie here... when you say to leave it in ready mode, do you mean leave the car on, but make sure the radio, etc. is turned off. Basically, park the car, but don't turn it off. This probably isn't as much an issue while it's warm here in PA, but once fall/winter comes, every little bit will help.

    Oh, and yes, I'll try calling the dog ahead of time - although he's usually ready to go before I am!

    Thanks again!
     
  6. ksstathead

    ksstathead Active Member

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    Correct, leave the car on with minimal electric drains. Some gen2 owners lock their car while getting groceries, etc., leaving it "on."
     
  7. bisco

    bisco cookie crumbler

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    it also depends on the time of year. right now, even tho it has to run the warm up cycle again, your average will only drop one or two tenths of an mpg.
     
  8. Colonel Ronson

    Colonel Ronson New Member

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    it takes hours for my car to cool down to the point the ICE restarts when i start the car to complete a warm up cycle. im talking 4-5 hours.
     
  9. ksstathead

    ksstathead Active Member

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    But you have a 2010...
     
  10. qbee42

    qbee42 My other car is a boat

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    Not for a Gen II. They do the restart every time.

    Tom
     
  11. Tideland Prius

    Tideland Prius Moderator of the North
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    Depends on the ambient air temperature. Obviously it'll cool down a lot faster in the winter than in the summer. If the engine's is fully warmed up (i.e. you've been driving around for 10-20 miles at least and it's summer), then 5 mins won't make that much of a difference. It'll still cool down but we're talking a few degrees, not enough to make it start in S1 all over again.

    When it's -20c on the other hand...
     
  12. priusevo

    priusevo Junior Member

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    So how do they lock the car and get back in after they exit? I have the base model and no smart key how would I accomplish this? Excuse me my brain a little fuzzy than usual since my wreck last week.
     
  13. MJFrog

    MJFrog Active Member

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    There's a metal key in the side of the FOB. You pull back a little slide and it comes right out. You can lock/unlock the car with the key. The key cannot be used to start the car.

    Of course you could always use the lock/unlock buttons on the FOB.
     
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  14. priusevo

    priusevo Junior Member

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    This could really come in handy to avoid the startup cycle if you were making multiple stops and were only away from the car for a few minutes at a time. Am I correct in thinking this?
     
  15. Rokeby

    Rokeby Member

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    My experience with "cooling down" on short periods of shut down for
    the Gen II suggests that the key is not block/coolant temps as
    measured by my ScanGauge.

    Yes, the Gen II seems to "want" to go through the whole warm-up
    routine after a short shutdown. But, it does so even if the block/coolant
    temps stay well above 157 degF.

    I think that lowered Catalytic Converter, CC, temps cause the new
    warmup cycle.

    If it is any consolation, from my observations, I also believe that the
    CC warms up rather quickly and there is a relatively quick return to
    fully warmed up, that is S4.
     
  16. MJFrog

    MJFrog Active Member

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    For the most part--true.
    However, I don't believe there is any way to bypass the (I think it runs for...) 57 seconds the ICE runs after you start up the car. If the water/cat temps are high enough I think it will go directly to S4 at ICE cut-off. Caution: my beliefs and reality are not always in sync.