650 vs 800 Output Difference - Why ?

Discussion in 'Parallel Universe' started by RicH2, Jun 11, 2010.

  1. RicH2

    RicH2 Ric H2

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    As I read it on BMW's web site, the F650GS & F800Gs have the same engine, yet the 800 has more Hp & torque.

    Why is that ?

    650 has single throttle body/injector ?
    650 is simply detuned ?
    650 has greater intake & exhaust restriction ?

    Can a 650 be mod'ed to reach the 800's hp & torque numbers ?
    #1
  2. huckleberry

    huckleberry BACK ROAD BOMBER

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    to the best of my understanding the difference is 1mm less lift in the cam and a different map in the computer. the 650 makes more hp and torque to 5,000 rpm the 8 makes more from there on.
    #2
  3. EnderTheX

    EnderTheX Dirt Rider

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    Even with the same engine body you can modify the cam to displace less volume. Doesn't the 650 actually displace 650cc (or 648 or whatever) and the 800 actually displace 798cc?

    I would imagine that reducing the amount of fuel/air you react each cycle has a great deal to do with your questions.
    #3
  4. TwIsTeD OfF

    TwIsTeD OfF The new hottness

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    The cam has nothing to do with cylinder volume (displacement). The 1mm less lift noted above doesn't open the valves as much.
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  5. RicH2

    RicH2 Ric H2

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    So one could use f800 cams....right ?
    And, are there the tools out there for modifing the engine controller mapping to suit the cam replacement ?
    #5
  6. Firefight911

    Firefight911 Been here awhile

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    The displacement is exactly the same between the F650GS (twin) and the F800GS. NOT to be confused with the F650GS (thumper) that has been renamed and is now called the G650GS.
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  7. peekay

    peekay Been here awhile

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    The difference in power output between the f650gs and the f800gs is negligible under 6000 RPM. If anything the f650gs might pull harder due to its lighter weight.

    So spending $$$ to modify the f650gs engine is likely not worth it. If you really need that much more power then the best way might be to trade to a different bike (e.g., the 1200GS).

    If you just want more torque then maybe just change the gearing.
    #7
  8. Dolly Sod

    Dolly Sod I want to do right, but not right now

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    Could always wait for bits to start showing up on EBAY. Bet in a bit of time the Computer and the Cams will be found for a song...


    ...unless everyone starts doing it.
    #8
  9. Dave92029

    Dave92029 Been here awhile

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    Traditionally dirt bike engines are designed to develop their peak power at low rpm. Who wants a dirt bike reving to 10,000rpm while riding off road.

    If you look at the wheels and suspension most people would agree (except on this list) that BMW designed the F800 with a dirt orientation and the F650 with more of a street orientation, BUT BMW got confused and put the street engine in the F800 and the dirt engine in the F650 :lol3 :lol3 :lol3

    I'll bet the guy who made that decision also decided to name the 800cc twin street bike - F650GS. I hope that genius is working for a different company. :evil :evil :evil
    #9
  10. raider

    raider Big red dog

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    I'd always thought the motors were the wrong way around too!

    But okay, here's the answer on why they cal it a "650" when it isn't. In some (quite big) European markets, there are licensing, tax and registration concessions applicable to machines with less than 660cc. It's why popular Euro-bikes like the XT660, SV650, NT650V, Monster 620, CB600, FZ6, XJ600 and so on adopt the capacities they do. These bikes act as "feeder bikes", the manufacturers hoping 19-year-old Pierre from Calais will buy, say, a CB600 and then migrate upwards to a CB1000 or a CBR.

    BMW, since they don't have a genuine 650-level entry bike (the then-F650 being a bit too narrow in focus and conservative for someone like young Pierre, and the more radical Scarver being less than a sales triumph), took a two-pronged approach.

    Firstly, in the absence of a proper 650, they dressed an 800 up to look like a 650 and market it in the same context as the FZ6 et al. They hope that buyers prepared to pay a little extra for the BMW badge either won't notice their bike doesn't get the sub-660 tax concessions until after they've bought it, or are prepared to pay a little extra for that, too.

    Secondly, they re-badged the F650 to be the G650, partly to re-align it with the factory's new nomenclature system but mostly to allow them to have a clean break from previous marketing efforts. With jazzy new, brighter colours and a marketing campaign that doesn't feature off-road riding at all, the G650 is hopefully pitched at young Pierre's slightly less-well off friend Hans from Frankfurt, who would also like some BMW cachet but needs the cheaper pricing and tax regime to afford it.

    This is the theory according to Raider :D
    #10
  11. SlowRide13

    SlowRide13 Veteran n00b

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    Sorry mate, but I just don't believe they put that much thought into it:lol3
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  12. peekay

    peekay Been here awhile

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    A big factor -- if not the biggest factor -- for marketing the detuned 800 as F650GS is to appeal to women riders who tend to prefer lighter, more approachable bikes with lower ride-height as compared to the F800GS.

    Women riders were a huge segment for the old F650GS single and continue to be an important segment for the new twin.
    #12
  13. raider

    raider Big red dog

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    Probably not, but it's a nice story :D
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  14. huckleberry

    huckleberry BACK ROAD BOMBER

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    Yea! nice story! its too bad they didn't give the 650 a wide ratio gear box and the 43mm forks the orignal specssaid it had cause then the 650 would be a great offroader!:lol3

    come to think of it i should have sued for false advertising on the forks cause that was 1 of the reasons i went with it, figured i could swap them out if they were junk which they are.
    #14