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Highway Speed: How Fast is Fast?

Discussion in 'Newbie Forum' started by mcamp52, Apr 12, 2009.

  1. mcamp52

    mcamp52 New Member

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    I have a "new" 2005 and took a 100 mile trip on the interstate for the first time this weekend. I am used to driving cars with tachometers and using that as a way of driving conservatively, without really winding up the car.
    On this trip a did a lot of cruising around 70 mph and avoided the temptation to go any faster. Overall, I averaged 47 mpg and I'm cool with that.
    But for future reference, does anyone know at what point the Prius is really "wound up" and running to fast? It's not like I want to drive like crazy but I do want to have a feel for not over taxing the car.
     
    #1 mcamp52, Apr 12, 2009
  2. efusco

    efusco Moderator Emeritus
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    It's fairly linear, you'll see the MPG drop, RPM rise with increasing speed.
     
    #2 efusco, Apr 12, 2009
  3. Tideland Prius

    Tideland Prius Moderator of the North
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    As Efusco said, it's fairly linear. If it's revving up there, you're probably cloes to 100mph.
     
    #3 Tideland Prius, Apr 12, 2009
  4. KCPrius

    KCPrius Member

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    I've taken several road trips and set the cruise at 80 and the engine does not seem to be straining at all. Mileage is in the high 30's at that speed. For what it's worth, I don't like to do a "cruise control pass" of slower moving vehicles going close to the same speed as me, so I will occasionally take it up to 90 to 95 mph. I don't keep it there long, but it still doesn't sound like it's straining at all.
     
    #4 KCPrius, Apr 12, 2009
  5. hobbit

    hobbit Senior Member

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    You might be interested in the little rundown on steady-state
    highway observations that I just posted over at CleanMPG.
    .
    I try to never go over 3 grand...
    .
    _H*
     
    #5 hobbit, Apr 12, 2009
  6. qbee42

    qbee42 My other car is a boat

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    Mostly the problem is aerodynamic drag. With aerodynamic drag the power requirements go up by the cube of the speed. I wouldn't say it's linear, except in the most crude approximate sense that mileage drops with speed.

    Tom
     
    #6 qbee42, Apr 12, 2009
  7. Habeepbeep

    Habeepbeep New Member

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    I've had my prius for 5.5 years and have driven up and down the East coast dozens of times. I usually set cruise control at 80-85 when I'm driving on I75 but in one case (fleeing a hurricane) I have reached 97mph. My prius seemed to do just fine and did not have much strain on it (granted it was a few years old at that point). I'm not recommending speeding, I'm just letting you know my own personal experience.
     
    #7 Habeepbeep, Apr 13, 2009
  8. richard schumacher

    richard schumacher shortbus driver

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    Go as fast and hard as you like. The computers limit engine RPMs in all circumstances.
     
    #8 richard schumacher, Apr 13, 2009
  9. mcamp52

    mcamp52 New Member

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    Thanks everyone. Great answers.
     
    #9 mcamp52, Apr 13, 2009
  10. danl

    danl New Member

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    Too fast for me is anything above 65mph. Only because my commute to work consists of mainly a 2 laner with a 45-50 limit.
     
    #10 danl, Apr 15, 2009
  11. Eoin

    Eoin Active Member

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    How fast is too fast? Simple. If you get a ticket, that's too fast.
     
    #11 Eoin, Mar 11, 2010
  12. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I spend a lot of time cruise controlling at 61 MPH (by the speedometer) on perfectly flat ground. 1900 RPM with the throttle 25% open. 69 MPH is closer to 2200 RPM. Once it quits being flat and/or you can't keep a constant speed, RPMs are all over, 980 RPM to 5000.
     
    #12 JimboPalmer, Mar 11, 2010
  13. F512M

    F512M Member

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    Ha, ha, ha I guess that's one way to look at it.:D
     
    #13 F512M, Mar 11, 2010
  14. puppeto

    puppeto New Member

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    Depending on terrain depends on where I stick the cruise. Here lately I've been down in the flatland of southern Mississippi so I've been setting to 63 to keep the MPG's up around 55. Further north into the mountains I don't bother with cruise and just feather it up and down hills.
     
    #14 puppeto, Mar 14, 2010
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