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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. JYoung

    JYoung Series 3

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    I'm not sure but I thought that I saw a CHP escort for Kari and Grant when they ran out of gas on the hypermile lap.
    Perhaps that prevented them from being victims of road rage.
    ;)
     
  2. jeff92k7

    jeff92k7 Annoyed with trolls

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    If you look closely, you can see Police escorts and traffic control in all their "on the road" segments. They do a pretty good job of editing it out, but you can still catch glimpses of them. Anything they have done on the public roads in the last few years has had a police presence (Blocking traffic, escort, shutting down roads, etc.)
     
  3. gschrock

    gschrock Member

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    There was an episode I think last season where they mentioned how they have to have police escort for anything they do on the roads.
     
  4. aaronw

    aaronw Member

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    Generally speaking, any car will be the most fuel efficient per mile in the topmost gear, at the lowest RPMs that will keep it from stalling in that gear. Fuel economy is directly tied to engine RPMs, and how 'much' those engine RPMs push you through the air. So, the more gears, the faster the 'most efficient' speed is, except that you run into air resistance at a point that may push you down a gear or two.

    As far as avoiding braking, sure. You want to keep your KE as high as possible, and if you have a lot of PE at the top of a hill, then at the bottom you'll have a lot of KE. Probably another tip for hypermiling is accelerate just enough (when possible) to coast over a hill when climbing it and then get all that KE back going down. As others point out, if you go over the top of a hill with a lot of KE, you may end up going quite fast and have to 'throw away' some of that energy (either via downshifting or breaking) on the way down. Electric cars with regenerative brakes can put some of that lost KE back into the system, whereas traditional brakes just turn it into heat.
     
  5. midas

    midas I heard that

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    I don't see how the long road test proved anything. As a simple, but extreme, example, lets say the first 50 miles was mainly flat highway driving. The first run, they get exactly 50 miles out of their fuel allocation. The second run they start the hypermiling. They get past their 50 mile mark, but at the 51 mile mark the road turns into pure uphill and for some reason it's bumper to bumper. They might get 5 extra miles before running out of fuel.

    So,did they only get 10% better mileage? Of course not. It could have been double. It could have been triple. The only way to tell is under identical conditions for the next 50 miles as they had on the first 50 miles.

    And with real traffic, you couldn't even guarantee that the first 50 miles of the trip were done under identical conditions. Either run could have had more traffic or different wind conditions.

    Finally, while they tried to follow hypermiling theory, none of them were well practiced experts. What they should have done was have one of those lunatic hypermiling nuts run the second leg at the same time the MB gang ran the first leg. And compare the fuel consumed at a measured distance rather than how much further they went.

    As always, this show is more about fun than true scientific proff.
     
  6. pteronaut

    pteronaut Killer of Threads

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    Volkswagen had dabbled with auto-stop/start systems for over 30 years, the 1981 Derby (EU Polo saloon) came with such a system in it's 1.1L 'Formel E' model.
     
  7. cwerdna

    cwerdna Proud Tivolutionary

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    Yep. I may be smeeking but the ep didn't really show how well they were hypermiling. For example, if they were approaching a red light, they should've shut off their engine at some point before the red light and just coasted to the intersection.

    I'm really hoping they can get hypermiling experts like Wayne Gerdes (http://www.motherjones.com/politics/2007/01/guy-can-get-59-mpg-plain-old-accord-beat-punk and http://web.archive.org/web/20090226062953/http://post-gazette.com/pg/05220/550484.stm) who runs cleanmpg.com for a redo. I think w/the proper instrumentation, he might be able to achieve 2x the mileage.
    Yeah, all Toyota hybrids from the 04 model year and beyond have an electric AC compressor. AC works just fine when the engine's off.

    On 2012+ model year Toyota hybrids, water pump become electric too so AC, power steering and water pump are all electric and there are no longer any "drive" belts.
     
  8. midas

    midas I heard that

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    Montgomery,...
    There's a big difference between a car with auto stop/start and doing it yourself. Most cars require the car to be in park to engage the starter. So it's stop at the light, put car in park, turn off, wait for light to change, start car, put car in drive, move car.

    That's a lot to go through at every traffic light. A car that had the function is simply stop, wait, go.
     
  9. cwerdna

    cwerdna Proud Tivolutionary

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    SF Bay Area, CA
    Umm, non-hybrid automatics I've driven can be restarted while in neutral.

    When I had my Z and learned about hypermiling, I'd FAS into a parking space (while still in D) and coast in. Once I'm stopped, I then shift to park.

    Most automatic drivers pull into a space, stop, shift to park, then shut off the car. There's a whole bunch of wasted engine runtime in there.

    Wayne talks about FASing into a parking spot at http://www.cleanmpg.com/forums/showthread.php?t=1510 under "Potential Parking". I generally tried that too, if I could find such a higher spot.

    For the traffic light, if it looks almost certain they will have to stop, they should FAS then coast in D or N. Once they've stopped, from N, they can restart and go to D.

    And yes, I have a Prius so I've been enjoying the engine seamlessly shutting down and starting up for over 7 years. :) I've also driven other hybrids and some BMW 3-series cars w/auto start stop.
     
  10. john4200

    john4200 Active Member

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    Agreed. I have most of the same objections as you to their scientific method. Sometimes Jamie and Adam do a decent job, and sometimes they have some serious holes in their methods. Tory, Kari, and Grant almost always have serious holes in their methods -- they are mostly in it just for fun.
     
  11. midas

    midas I heard that

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    Most, but not all. Either way, it doesn't matter. I still find it very annoying and distracting. It's still a very different driving experience compared to an auto stop/start system.
     
  12. RonDawg

    RonDawg Well-Known Member

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    All that extra momentum won't do you any good if you can't stay planted on the road and end up crashing. A good hypermiler will know where he/she will have to slow down due to a tight corner, and let their speed naturally scrub off before they get to that point. It's really no different than anticipating stop lights and stop signs.
     
  13. RonDawg

    RonDawg Well-Known Member

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    I got used to it very quickly. I don't know about the Hyundai, but on the BMW there is an area on the tach to indicate if the engine is in "standby" as opposed to totally off (0 RPMs).

    On the BMW, yes you can turn it off. It's just above the starter button. If the car senses a need to run the engine for some reason (for example, heater usage) then it will do so.
     
  14. RonDawg

    RonDawg Well-Known Member

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    Even with the CHP escort, a car still honked at Tory and (according to him) the female driver flipped him off.

    45 MPH on any California freeway is just plain crazy unless everybody else is doing that speed. Many freeways that are posted at 55 still have traffic going by at 65+. Bay Bridge is posted 50 up to the temporary s-curve, and even then people are racing to that curve at 70, and going through the curve at higher than the posted 45 limit.
     
  15. RonDawg

    RonDawg Well-Known Member

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    It's not legal (certainly not in California where this was filmed) and quite dangerous if you let your speed get out of hand. It's even worse if you tried to control your speed by "riding" the brakes, because if they are overheated, they don't work at all.

    From what I've been told on this very forum, on a modern fuel injected car if you downshift in order to control your speed on a downhill run, and don't put your foot on the gas, the engine is using zero fuel and is just one giant air pump powered by gravity, so you're not using any gas whatsoever.
     
  16. RonDawg

    RonDawg Well-Known Member

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    Problem with that is on a non-hybrid, you lose power braking and steering assist once the engine is off. Definitely not recommended on San Francisco's hilly streets.
     
  17. john4200

    john4200 Active Member

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    Really? If only I thought of that before my last crash. :rolleyes:
     
  18. Waldorf

    Waldorf Super Duper Member

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    I have two BMW's as well as a "fun" car and you can really sense the engine running at stops. On this hybrid (and most others, I imagine), it's just kind of strange to be sitting there with no vibration coming through the car as if it died. And yes, like others have stated, the radio and a/c and everything will still run off battery, I'm just not sold on it yet as I feel disconnected from what's going on.

    Has anyone tried the Honda CR-Z? I have read it has a 6-speed manual transmission option on the hybrid. Sounds interesting.
     
  19. RonDawg

    RonDawg Well-Known Member

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    I'm not sure why you're being so snarky here.

    Yes I can understand why a hypermiler doesn't want to slow down. But driving in real life conditions means eventually you have to slow, if not come to a stop. A hypermiler will anticipate these and try to let the car naturally scrub off speed before getting to such an area, rather than racing up to red lights and stop signs as I often see.

    I was also only commenting on their assertion that their methods are legal and safe. 45 on a posted 65 is borderline rolling traffic hazard, and taking curves so fast that you cause the tires to squeal means you're on the verge of losing traction.

    BTW I drive an all-electric car as my commuting car, so I'm acutely aware of these techniques myself. When your usable range per charge is only in the double digits, you learn to adapt real quick.
     
  20. Waldorf

    Waldorf Super Duper Member

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