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When to take them out

Discussion in 'Gen 2 Prius Fuel Economy' started by rickt, Mar 17, 2009.

  1. rickt

    rickt New Member

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    I have an '09 with about 4200 miles. Several months ago I blocked four grill openings and increased the tire pressure (42 and 40) with the hope of negating some of the mileage loss from the miserable Twin Cities winter. Mileage increased from mid/high 30s to low/mid 40s so I assumed these actions did what they were designed to do. The past few days temps have jumped into the 50s and low 60s. Should I remove the grill blocks? Am I risking overheating or damaging the engine with the higher outside temps?

    Is it recommended to run the higher tire pressure year around?

    Advice is appreciated!

    rickt
     
    #1 rickt, Mar 17, 2009
  2. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Here's what I usually adhere to (when I remember):
    < 70F : full block
    70 - 75F : bottom 2 or 3 of the bottom section removed
    75 - 85F : bottom fully removed
    > 85F : Fully unblocked.

    There are many people on the board with the Scan Gauge who can monitor their engine temps. They can be more precise in their usage. I do not have one.

    Always start unblocking from the bottom because that's where the inverter is and you don't want that overheating. And keep in mind that this is your car and ultimately you make the decisions on how to use it. Any advice provided on this board - good or bad - should not override your internal "should I do this" meter.
    (the lawyers made me write that)
     
    #2 TonyPSchaefer, Mar 17, 2009
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  3. efusco

    efusco Moderator Emeritus
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    50s and 60s will be fine and no risk of damage. When you start seeing upper 60s to 70s I'd remove at least one or two grill blocks.

    And yes, run higher pressures year around.
     
    #3 efusco, Mar 17, 2009
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  4. CharlesJ

    CharlesJ Member

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    I had that dilemma. I got the scangauge, not for this specific dilemma, and monitored the intake air temp and water temp.
    As the temp started to get to 60 and above, water temp started to climb and bounce back and forth from about 185 to 200/205 and intake air to about 80 and after short stops to 100. Pulled the top one from the bottom grill, IA is around 65 now and about 185 water; haven't seen the 200 since. But, all this could be just poor testing:D
     
    #4 CharlesJ, Mar 19, 2009
  5. JimN

    JimN Let the games begin!

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    I keep the top blocked year round and block the bottom 80%. I unblocked the bottom in June last year. If the fan starts then it is getting too hot.
     
    #5 JimN, Mar 20, 2009
  6. tochatihu

    tochatihu Senior Member

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    Presumably CharlesJ temperature bounce resulted from radiator fan cycling. Since the underlying goal here is fuel economy, when that fan motor starts it's time to open up. Probably goes without saying that air conditioning use should also have an open front.

    As far as risk of overheating the engine coolant loop I think that's quite low overall. On the other hand you want the inverter coolant loop as cool as possible always. I'm not too clear on whether the various NHW20 grill blocking procedures interfere with inverter cooling.

    On the NHW11 you can just put a piece of cardboard in front of the radiator :)
     
    #6 tochatihu, Mar 20, 2009
  7. fishvail

    fishvail New Member

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    What are you guys talking about re: blocks? And, can you tell me why, in the past 6 months, my mileage has been stuck on 39-40 mpg? I have an '04, so am not a newbie with my Prius. It has 105,000 miles on it, and I've always had at least 46 mpg and never thought anything of having 55-60. What has happened??
     
    #7 fishvail, Mar 21, 2009
  8. CharlesJ

    CharlesJ Member

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    Thanks, that is good to know and that it works as advertised:D
     
    #8 CharlesJ, Mar 21, 2009
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