GUIDE: Why scooters dont go 90-100mph+.

Discussion in 'Scooter Guides' started by tErr0, Feb 20, 2011.

  1. tErr0

    tErr0 Administrator Staff Member

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    A lot of people either claim or hope their scooters do large top speeds when they tune them. This however is pretty much never the case no matter how many parts you bolt on or tuning you get done. In this topic I will explain why this happens and try to get you to understand what sort of tuning you will need to do to reach a certain top speed.

    As with any object a scooter needs more power to reach a higher speed but as you go faster you need more power to push through the air. Cars have a much easier job as it's all nice smooth body work and glass going through the air and not lots of pointy out bits and a body. Most scooters are generally pretty terrible when it comes to aerodynamics so for this topic I'll be sticking to one set of figures rather than differentiating between models. The figures we are after are Drag Coefficient and Frontal Area. We also need an idea of the weight of the bike and rider but this doesn't actually effect top speed hugely when you are changing it only slightly.

    Now the Drag Coefficient is basically how well the front of the bike moves through the air. Scooters aren't really designed to go through the air as at low speeds this doesn't really matter and most scooters are only really designed for low speeds. You can read up on it in more detail here http://en.wikipedia.org/wiki/Drag_coefficient.

    Frontal Area is just a measurement of the front of the bike which is pushing through the air. A bigger amount is worse as the more mass you are trying to put through the air the more resistance you will get even if it has a nice smooth shape.

    The figures I have come up with from looking around are 1.0 for Drag Coefficient and 0.56 metres squared or about 6.02 feet squared for the Frontal Area.

    1.0 Drag Coefficient is a good guess due to most sports bikes being around 0.6 and a person standing upright is around 1.0 - 1.3. I will give links later to charts of different vehicles/things and their Drag.

    0.56 meters squared is what I have come up with myself. This is a pdf that gives a guys ideas of measurements of the front of a Vespa PX i've taken into consideration these and come up with a slightly higher reading due to basing it on Gilera Runners or Piaggio Typhoons which are quite a bit larger than a PX. I am aiming to go out and measure a Typhoon up to get a slightly more accurate reading.

    Now for the actual calculations and results.

    The easiest way I could find to show and explain these was to find and use an online calculator so you could see the results for yourself. The one I ended up using was this http://www.rbracing-rsr.com/aerohpcalc.html.

    If you enter the figures I gave you already so 1.0 for Cd and 6.02 for frontal area plus a weight of 428 lbs which is about the weight of a Gilera Runner with a 12 stone person on it. Then you put the speed which you would like to go, or are interested in finding out the bhp needed, you should get the results.

    Here are some results and what sort of tuning you would need to get there.

    30mph = 1.64bhp. Much less than a restricted 50cc which normally have around 3.5bhp.
    40mph = 3.52bhp.
    45mph = 4.82bhp. The 45-50mph bhp figures are about spot on for a de-restricted scooter which can range from 4.5 to 6.5.
    50mph = 6.47bhp.
    60mph = 10.94bhp. Getting into the sport 70cc kit bhp figures and also 125cc 4 stroke bhp specs and 100cc's.
    65mph = 13.76bhp. More like the Mid race 70cc kit bhp and the stock 125cc 2 stroke bhp.
    70mph = 17.05bhp. A 125cc with just a 172cc kit fitted is around 17bhp and you will now start seeing the bhp figures increasing a lot for not much more mph.
    75mph = 20.82bhp. A 172cc with pretty much all the bolt ons.
    80mph = 25.05bhp. A street ported 172cc bike with all the bolt ons is around this.
    90mph = 35.41bhp. Now you are talking some serious porting and hardly any reliability without a lot of maintenance. Pretty much a sprint bike.
    100mph = 48.23bhp. Not even a figure that is reachable by tuning a scooter without nos.

    The findings seem to totally agree with what I have found personally when riding scooters and what others have when not referring to the totally inaccurate speedos.
     
  2. bandyleg

    bandyleg New Member

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    Re: GUIDE: Why scooters don't go 90-100mph+.

    :good: :thumbsup:
    Nice to see someone put into perspective what you can expect from your bike!!
    Very nice and a good read!!
     
  3. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

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    Re: GUIDE: Why scooters don't go 90-100mph+.

    remember these are engine power figures not rear wheel... the rear wheel, gearing loss aswell as any times UPTO these speeds are irelevent, this is mearly if your crank was permanently attached to your wheel and you were geared for these exact speeds you would need these flywheel figures of bhp to attain the speed on the road.


    this is why when there is an 80mph wind and you drive with it you are able to do stupidly high speedfs. unfortunatly the wind allways faces you at pod LOL
     
  4. tErr0

    tErr0 Administrator Staff Member

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    5,816
    Re: GUIDE: Why scooters don't go 90-100mph+.

    I probably should have said a bit more that the actual bhp figures are pretty irrelevant as they can vary from dyno to dyno, at the crank instead of rear wheel, etc etc. It's more looking at the difference in power in relation to speed.
     
  5. grantmc3

    grantmc3 Member

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    piaggio nrg mc3
    Re: GUIDE: Why scooters don't go 90-100mph+.

    why isit peaple claim that there 172 can reach 100+mph are they just dreamin lol maybe they had wind behind them down a steep hill with a dodgy speedo
     
  6. EVERITT sr

    EVERITT sr New Member

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    Aprilia SR 125
    Re: GUIDE: Why scooters don't go 90-100mph+.

    What about PMtuning they hit 104 without nos ?
     
  7. tErr0

    tErr0 Administrator Staff Member

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    5,816
    Re: GUIDE: Why scooters don't go 90-100mph+.

    By using a sprinter which has a hell of a lot less weight and means you are going through the air a lot easier. The guide is all about drag.

    Plus they weren't useing something that even comes close to a 172 kit.

    [​IMG]

    [​IMG]
     
  8. mrhappy

    mrhappy Member

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    177
    Re: GUIDE: Why scooters don't go 90-100mph+.

    wots the top speeds ppl getting then out there bikes?
     
  9. robhall123

    robhall123 New Member

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    267
    Re: GUIDE: Why scooters don't go 90-100mph+.

    55 ish
     
  10. mrrob27

    mrrob27 New Member

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    11
    Re: Re: GUIDE: Why scooters don't go 90-100mph+.

    71mph, but never do, it's unnecessary :)

    Sent from my GT540 using Tapatalk
     
  11. roxi-46

    roxi-46 Member

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    87
    Re: GUIDE: Why scooters don't go 90-100mph+.

    great guide, real helpful! love it for proving scabby kids that think they're bikes go "70-75" wrong! :cheers:
     
  12. Jonnymarrw00t

    Jonnymarrw00t Moderator Staff Member

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    Re: GUIDE: Why scooters don't go 90-100mph+.

    "100mph = 48.23bhp. Not even a figure that is reachable by tuning a scooter without nos."
    If I'm right to believe the new Evo Engine on Nrg wheels can do over that ? I know it would be shit for road use but would be one hell of a ride with out a doubt.
     
  13. lshigham

    lshigham Member

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    250
    Re: GUIDE: Why scooters don't go 90-100mph+.

    PSN have told me that 38bhp is the least they would expect for a 183 in order for it to be competitive on the circuit.
     
  14. NRG46

    NRG46 New Member

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    Typhoon
    Re: GUIDE: Why scooters don't go 90-100mph+.

    didn't tdr make a 178 that did the quarter mile at 103mph?:L without nos assistance.
     
  15. tErr0

    tErr0 Administrator Staff Member

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    5,816
    Re: GUIDE: Why scooters don't go 90-100mph+.

    The amount of people that don't actually read the guide and just read the little bit at the bottom is amazing.
     
    Merlin, speedy22 and billyd05 like this.
  16. NRG46

    NRG46 New Member

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    Re: GUIDE: Why scooters don't go 90-100mph+.

    cry me a river? :)
     
    Cory Cole-Wilkins likes this.
  17. martain

    martain New Member

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    Re: GUIDE: Why scooters don't go 90-100mph+.

    im 28 and i dont think this is right but hey if i get proven wrong fair play but i reckon i can get a 50/70 to do 100mph

    there is old circuit geared bikes that are 50's and do over a 100 mph so i think ya bhp = mph is bollox but hey that is my opinion i may be wrong but im gonna try prove im right :)

    http://www.ultimatemotorcycling.com/1963-suzuki-50cc-grand-prix-racing

    so correct me if im wrong 50cc doing over 100 so 70cc shud be a piss easy and 1960@s ok so the have like 8 speed trannys and rev up to 20k but wheres there carbon fibre race reeds and other hi tech equipmemnt they had basics so im gonna have to disagree with this post


    sorry if i shat on ya parade but so many people say its not possible there wrong!
     
    Cory Cole-Wilkins likes this.
  18. NRG46

    NRG46 New Member

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    Typhoon
    Re: GUIDE: Why scooters don't go 90-100mph+.

    100mph = 48.23bhp. Not even a figure that is reachable by tuning a scooter without nos.. Not trying to argue but states that ..its not even a figure unless with nos.
     
  19. tErr0

    tErr0 Administrator Staff Member

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    5,816
    Re: GUIDE: Why scooters don't go 90-100mph+.

    Again read the actual article. The article is about aerodynamics and not about power and the final bit is just to show how the amount of bhp needed increases hugely between just a few mph the higher speeds you get to.
     
  20. NRG46

    NRG46 New Member

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    Typhoon
    Re: GUIDE: Why scooters don't go 90-100mph+.

    I know and i didn't say anything about the BHP i just said didn't tdr do a 100+ mph scoot without nos... And you have stated that there's no such thing :) Only asking so don't get all defency about it all dude (Y):L
     

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