why do motorcycles get (relatively) poor MPG?

Discussion in 'OT Driven' started by AVengeance, Jun 26, 2009.

  1. AVengeance

    AVengeance Active Member

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    Kawasaki's website has a neat feature where they show the MPGs of many of their bikes, from 90-something down to 34 or so mpg. Why do some of these bikes, which have 1.5L engines or smaller, only get 35-40mpg, when a Neon, Focus, or Cobalt can pull off the same feat with all that extra weight?
     
  2. Morgan06

    Morgan06 New Member

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    How many RPM is a Neon, Focus, or Cobalt capable of?
     
  3. AVengeance

    AVengeance Active Member

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    The stock Neon DOHC 2.0L rev limiter is 7200. I don't see how that makes a hill o' beans in this matter, though. If you took a 2600lb 1st gen Neon that got 35mpg, and put all kinds of lightweight stuff on it (aluminum body, billet Al and Ti brackets, aluminum engine block, mag wheels, etc.) and dropped the weight to 1800lb, wouldn't it get even better gas mileage? I'd say around 38mpg. What happened if you took that same 2.0L i4 and stuck it in a motorcycle, and had a total wet weight of just 750lb?
     
  4. Junkie

    Junkie re-tarded OT Supporter

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    there's a lot of aerodynamic drag on bikes
     
  5. AVengeance

    AVengeance Active Member

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    Last edited: Jun 26, 2009
  6. Thomas Crenshaw

    Thomas Crenshaw New Member

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    most people on bikes arent shifting at 25-3500
     
  7. GammaRadiation

    GammaRadiation Active Member

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    Because you dont understand physics.

    MPG only has to do with weight while accelerating.
     
  8. 7960

    7960 New Member

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    so these get the same mpg when cruising at a constant speed?


    [​IMG] and [​IMG]
     
  9. NetChemica

    NetChemica OT Supporter

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    no, but at 65mph this car gets much better gas mileage than most bikes out there

    [​IMG]

    shit, even around town it gets better gas mileage
     
  10. 7960

    7960 New Member

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    at 65 mph my harley gets around 55 mpg.

    what's the vw get?
     
  11. Raider007

    Raider007 om nom nom nom

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    my bike

    [​IMG]
     
  12. 7960

    7960 New Member

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    :(

    I've only ridden about 1000 miles so far this year. But I've probably only driven my car about 800 miles since Jan, so I guess 1000 miles on the bike isn't bad.
     
  13. º¿º

    º¿º OT Supporter

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    :bowdown::bowdown::bowdown::bowdown::bowdown::bowdown::bowdown:
     
  14. º¿º

    º¿º OT Supporter

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    is that some type of widget or what :o
     
  15. Raider007

    Raider007 om nom nom nom

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    I think i've put another 1000 since that screenshot...

    http://www.appcubby.com/gas/index.html
     
  16. º¿º

    º¿º OT Supporter

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  17. AVengeance

    AVengeance Active Member

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    Nice find. I keep mine in an Excel spreadsheet, and keep a small notepad in the cars to write it down. So for my EX250 is at 61.8mpg- right at what Kawasaki claims. What was your 53mpg run- stand on the footpegs all the way to work one day? :rofl:

    I've got 700 miles on my bike already, just got done with the 600 mile work (had the shop do it, then my svc manual shows up the next day- go figure). I'm loving the bike so far, and 61mpg sure beats the Durango, at 15.
     
  18. igotyofire

    igotyofire New Member

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    change the gearing on your bike and ull see mileage increases...
     
  19. GammaRadiation

    GammaRadiation Active Member

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    Physics, take a class. ;)
     
  20. 7960

    7960 New Member

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    sense, make some :rolleyes:
     
  21. GammaRadiation

    GammaRadiation Active Member

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    It's a basic law of inertia.

    Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless there is an outside force acting on the object. In the case of an object moving through an atmosphere, the only force acting on an object traveling at speed is wind resistance.

    Ke=1/2 MV^2

    M is constant, so when V is constant, the amount of energy is constant and, therefore, mass has nothing to do with MPG at a constant velocity.

    However, when accelerating (in any direction) mass has a lot to do with MPG, and since most driving isn't constant, yes weight will affect MPG. If I wasn't running out the door right now I'd even show how a minor mass difference can make a big difference in fuel consumption. :)
     
  22. 7960

    7960 New Member

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    I understand you're trying to sound important, but you're leaving out one little thing. The mpg a vehicle gets has as much to do with the area of the front of the vehicle as it does anything else.

    So before we get in this pissing match, explain this statement.

    the bus gets 8mpg. the motorcycle gets 60mpg. what does "MPG only has to do with weight while accelerating" have to do with that?
     
  23. GammaRadiation

    GammaRadiation Active Member

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    :rofl::rolleyes:

    When you're not accelerating MPG has EVERYTHING to do with aerodynamics and the efficiency of the motor and nothing more. Unless, of course, you're going up or down a hill and then, again, mass has a lot to do with MPG. Heavy vehicles get better MPG while going down hill and worse MPG while going up (or better said, a greater increase/decrease than a lighter vehicle).

    If you really dont understand inertia, please stop teaching. EVERY teacher, regardless of their subject area, should have the intellect to understand basic Newtonian physics.

    Take the air out of the equation and once you're up to speed you can just put the vehicle in neutral and continue traveling at the same speed no matter the mass. Thus, when traveling at a constant speed the only thing slowing you down (ie, taking energy away) is drag. If you really want to be specific, rolling friction is also a factor but to the point that removing all rolling friction would barely produce a change.

    Edit: If you dont believe it, how do you think moving satellites stay in orbit? We dont fuel them, they have no rocket boosters. They must maintain a certain velocity in order to not fall down. Because there is nearly a perfect vaccuum there is hardly any friction. They stay in orbit merely on their own kinetic energy.
     
    Last edited: Jun 29, 2009
  24. GammaRadiation

    GammaRadiation Active Member

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    To answer the original question, bikes are not aerodynamic, run at very high revs (low small load efficiency), and are often carburated (poor efficiency) or fuel injected tuned for power, not efficiency.

    Look at scooters. Even the bigger ones can get 100+ MPG because they are more aerodynamic and have motors tuned for efficiency instead of power.

    Cars are more aerodynamic, run at lower revs, and are usually tuned for efficiency unless they are performance vehicles.
     
  25. diaper eater

    diaper eater OT Supporter

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    because my bike hits 14k rpm on every ride it takes. car rarely hits 4k or 5k
     

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