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Mythbusters 6/12/2013 - Hypermiling and Crash Cushion

Discussion in 'Now Playing - TV Show Talk' started by GoPackGo, Jun 13, 2013.

  1. GoPackGo

    GoPackGo Active Member

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    Dec 28, 2012
    Something about the synthetic cadaver was absolutely terrifying.

    Of course Adam had an old Volvo!

    I found it really annoying how they danced around ever saying that the police officers were fat. Plus sized. Big. Large. Wide. Heavyset. Just say fat!
     
  2. john4200

    john4200 Active Member

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    They said they have used 44 Buster variations over the years!

    Did they mention the title of the movie that had the guy between the two fat cops in the car accident? I remember the scene, but I cannot remember the rest of the movie (or the name).
     
  3. Kamakzie

    Kamakzie Are you serious bro?

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    I think they said the movie was called Headhunters?
     
  4. Church AV Guy

    Church AV Guy Active Member

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    high desert...
    I thin you can extend your gas mileage by driving at 45MPH on the freeway, but at the expense of vastly shortening your personal lifespan.

    That was quite the impact when the truck hit the car. I too thought the cops would provide cushion.
     
  5. secondclaw

    secondclaw Member

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    Florida
    Jamie did say fat before the last test.
     
  6. GoPackGo

    GoPackGo Active Member

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    You're right. I wrote my statement before my viewing of the episode had ended.
     
  7. john4200

    john4200 Active Member

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    Thanks, that is it. Now I remember.
     
  8. JMikeD

    JMikeD Member

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    Austin, TX
    Depends on the car. The "sweet spot" for economy seems to be in the 40-60 mph (according to auto websites), but depends on gearing, aerodynamics, weight, etc. In general, smaller, lighter, more aerodynamic cars will get their best mileage at the higher end of that range. Bigger, heavier, less aerodynamic vehicles will get their best mileage at lower speeds.
     
  9. gschrock

    gschrock Member

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    holt, mi
    And yet, the best gas mileage I ever got on my old grand cherokee was travelling across south dakota, where I got about 22 mpg, and the speed limit there at the time was around 75. (I did a lot of expressway driving on that trip, and even in other states, like I think it was iowa where it was a brutal 55, always did less on gas mileage.)
     
  10. john4200

    john4200 Active Member

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    If everything else were equal, there is zero chance that a Grand Cherokee would get better gas mileage at 75mph than 55mph. The air resistance at 75mph is much higher than at 55mph, especially for a vehicle shaped like a GC. Any engine efficiency vs. rpm factors are going to be swamped by the much higher air resistance at 75mph.

    So, to explain your findings you have to look at other factors. One would be whether you measured the gas mileage accurately and whether you remember correctly. Another important factor is headwinds and tailwinds. Traffic (varying speeds). Hills and mountains. Tire pressure. Whether windows were open. Air conditioning. Load. And others.
     
  11. vman41

    vman41 Omega Consumer

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    In my experience, 45 MPH is where transmissions generally shift into overdrive, so getting best mileage there is not surprise. My current car is 5 years old and just missed the transition to transmissions with more gears, so there might be a sweet spot now somewhat higher up.
     
  12. scooterboy

    scooterboy Coney Island Small

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    Mar 27, 2001
    East...
    So what were their (general) findings on hypermiling?
     
  13. john4200

    john4200 Active Member

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    You can increase your mileage by following several techniques that they tested, but it is difficult, and you cannot double your mileage. Also, although not stated, it was seen rather clearly that it may not be worth following several of the techniques unless you are really desperate to increase your mileage: windows up and A/C off was brutal; 45mph on the highway was causing traffic jams and getting other drivers angry; turning off the engine at a red light often resulted in very slow off the mark and honks from other drivers; avoiding braking on downhill runs made the passenger cringe when it felt like the car was nearly out of control.
     
  14. secondclaw

    secondclaw Member

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    I've done hypermiling when running out of gas, and thought their finding on A/C versus open windows from an earlier episode was pretty interesting. I was actually hoping they would do another HM thing - accelerating 5mph above posted speed limit then coasting down ... I've always been curious if that method actually does anything but been too lazy to try it myself. I suppose they don't want to break the law on TV, even if its a 5mph over limit.
     
  15. RonDawg

    RonDawg Well-Known Member

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    They also said these methods were legal and going 45 on a posted 65 freeway (as many of those stretches were) is at the very edge of legality, if not safety. I would never recommend anybody drive at that speed on a California freeway unless conditions are such that you really shouldn't go any faster, such as during a rainstorm, and I certainly wouldn't go into the left lane like Tory did in one shot.

    Turning off the engine at traffic lights has already been proven and has been incorporated into auto stop-start systems. When I was in Europe last year, I rented a BMW with auto stop-start and I didn't find it to be a problem at all. The car started right up with almost no delay once I took my foot off the brake.

    They could have also controlled their speed on the downhill stretches by simply downshifting the transmission and taking advantage of engine braking.
     
  16. Waldorf

    Waldorf Super Duper Member

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    Phoenix, AZ
    I'm currently driving a Hyundai Sonata Hybrid rental and find the engine cut-off at stops to be a bit unnerving. Starts right up like a golf cart, though.
     
  17. vertigo235

    vertigo235 Active Member TCF Club

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    I assume you can turn it off. What about those times when you're in heavy traffic and Need the air conditioner while you're stopped?
     
  18. john4200

    john4200 Active Member

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    No, you missed the point. They were avoiding braking of any kind in order to keep their momentum up and save fuel. If you brake (with the brakes, or the engine) before going into a turn, then you need to use more fuel later to speed up again.
     
  19. Hank

    Hank AC•FTW TCF Club

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    They prob could have shifted into neutral on the down slopes and idle the engine, but I know that's not generally legal.
     
  20. brianric

    brianric Active Member

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    Pennsville, NJ
    The 2012 Camry Hybrid has electronic air conditioning and water pump.
     

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