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Thread: Motorcycle CdA Values

              
   
   
  1. #1
    Electric Warrior CaptainKlapton's Avatar
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    Motorcycle CdA Values

    With a growing number of people interested in simulations (myself included), I thought it might be useful to have a table of CdA values to refer to.
    Most of the values are from wind tunnel tests with the sources at the bottom of this post.
    If you know of any verifiable values I am missing, feel free to post or PM them to me and I will tack them on.

    Machine: Prone CdA (m^2), Upright CdA (m^2)

    Aprilia
    *Aprilia AF1: 0.291, 0.444
    @Aprilia RSV1000Mille 0.301, ----
    _Aprilia Mille: 0.520, 0.610

    Bimota
    *Bimota DB1: 0.319, 0372

    BMW
    ***BMW K1: 0.340, 0.380
    ^BMW K100RS: 0.402*/_0.400 , 0.429*/_0.430
    *BMW R100RS (0.401), 0.435
    *BMW K75S: 0.414, 0.439
    *BMW K100RT: (0.456), 0.495
    _BMW R1100RT: 0.530, 0.970

    Buell
    @Buell RR1000: 0.251/0.280 no turn signals or mirrors/street trim ----
    @Buell S2/S3: 0.323, ----

    Corbin
    @Corbin-S1 0.268, ----

    Ducati
    *Ducati Paso: 0.331, 0.459
    *Ducati 750SS: 0.341, 0.438
    _Ducati 916: 0.490/0.570/0.530, 0.610/0.690/0.610

    Honda
    **Honda RS125 GP (1990): 0.193, (0.277)
    **Honda RS125 GP (1996): 0.204, (0.303)
    *Honda RS500(1984): 0.243, (0.360)
    @Honda CBR600F3: 0.325, ----
    *Honda CBR1000F: 0.349, 0.438
    *Honda VFR750F: 0.366, 0.447
    ^Honda VF1000F: 0.400* /_.400, 0.455*/_0.46/_0.45
    _Honda Blackbird: 0.440/0.490, 0.720/0.810
    *Honda XL600 Transalp: (0.474), 0.515
    _Honda V65 Magna: ----, 0.610

    Kawasaki
    ^Kawasaki ZX-14R: (0.315) 0.344****, (0.422)
    ****Kawasaki ZX-10R: 0.340, (0.415)
    ^Kawasaki ZX-12R(2001): 0.341**/_0.340, (0.416)
    *Kawasaki GPz1000RX: 0.354, 0.474
    ^Kawasaki Gpz900R: 0.361*/_0.360, 0.443*/_0.430
    *Kawasaki KLR600: (0.520) , 0.565
    *Kawasaki 1000GTR: (0.557) , 0.605

    Moto Guzzi
    @Moto Guzzi GP V8: 0.186, ----

    Suzuki
    @Suzuki GSX-R600 ('98) 0.270/0.300 no signals or mirrors/ stock, ----
    ^Suzuki Hayabusa: @0.270,0.313**/0.332****/_0.310, (0.384/0.407)
    ^Suzuki GSX-R750(2001): 0.324**/_0.320, (0.395)
    ****Suzuki GSX-R1000: 0.332, (0.405)
    **Suzuki Bandit 600: 0.366, (0.449)
    *Suzuki GSX-R1100: 0.398, 0.430
    *Suzuki GSX-R750(1987): 0.410, 0.455
    ^Suzuki GSX1100EF: 0.412*/_0.410 , 0.444*/_0.440

    Triumph
    Triumph Speed Triple R: (0.453) , (0.492)

    Vincent
    *Vincent Black Prince(1953): (0.517), 0.562

    Yamaha
    *Yamaha TZ250(1985): 0.269, 0.366
    *Yamaha TZR250: 0.296, 0.421
    _Yamaha OW69: 0.320, ----
    *Yamaha FZR1000: 0.351, 0.404
    ^Yamaha FJ1100: 0.433* /_0.430, 0.483*/_0.480
    Yamaha R5: (0.422) , (0.458)
    ^Yamaha R1(1998): 0.570_/@0.283/ @0.314 no signals or mirrors/stock, 0.620
    _Yamaha Venture: ----, 0.75

    Averages by Class:
    Faired sport bike: 0.363, 0.445
    Naked sportbike:---
    Standard:0.394, 0.491
    Cruiser:---
    Sport touring: ---, 0.775
    Dual sport: 0.440, 0.540___ limited data

    Average CdA Deltas:
    For CdA values ranging from 0.19-0.3 while prone, upright value is ~43.8% higher.
    For CdA values ranging from 0.3-0.4 while prone, upright value is ~22% higher.
    For CdA values ranging from 0.4-0.5 while prone, upright value is ~8.7% higher.


    The following is from Motorcycle Dynamics
    Typical Frontal Areas by Class:
    “Super” Bikes: 0.3-0.35m^2
    GP Bikes: 0.22m^2 or less
    Touring/ partial fairing: 0.4-0.5m^2
    Naked Bike w/ upright Rider: 0.7m^2

    Typical Drag Coefficient and Frontal Area Pairs:
    Typical drag coefficient(naked): 0.65-0.7
    Typical Frontal area(naked): 0.6-0.7m^2
    Typical drag coefficient(w/ fairings): 0.55-0.65
    Typical Frontal area(w/ fairings): 0.4-0.5m^2

    Typical CdA Improvements:
    Front fairings decrease CdA by ~0.02-0.08m^2
    Side fairings decrease CdA by ~0.015m^2
    Rear fairings decrease CdA by ~0.015m^2
    Saddlebags(properly designed) decrease CdA by ~0.02m^2
    5-20% improvement in CdA by riding prone


    * Data published in Motorrad, March 1987
    ** Data published in Sport Rider, June 2001 http://www.sportrider.com/tech/146_0106_aero/
    *** Source: Motorcycle Review 1989 http://www.motorcyclespecs.co.za/mod...mw_k1%2091.htm
    **** Data published in Sport Rider, October 2006
    _ Data published in Tony Foale's "Motorcycle Handling and Chassis Design"
    ^ Multiple sources
    ( ) Calculated value based on averages of the different groups
    @ From a post on BadWeatherBikers
    Bikes without any marks have purely calculated values
    Last edited by CaptainKlapton; 08 May 2014 at 1218.
    "Never let schooling interfere with your education."
    -Mark Twain

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  3. #2
    Empulse R #24 frodus's Avatar
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    Crouching a bit and sitting full upright IIRC
    Travis

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    Electric Warrior CaptainKlapton's Avatar
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    Dang it! I always forget something.
    Prone CdA is the drag area when the rider is crouched, and upright CdA is when the rider is in a more natural position.
    Because the drag coefficient(Cd) is dimensionless, its product with frontal area(A) has the same units as area, square meters (m^2).

    Edit:Travis beat me to it
    "Never let schooling interfere with your education."
    -Mark Twain

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    Seņor Member podolefsky's Avatar
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    This is great, gives good numbers to enter in the elmoto spreadsheet.

    Could you produce some typical (maybe average) numbers for, say, faired sport bike, naked sportbike, standard, cruiser, dual sport, etc? Would be really useful if your bike isn't listed or is custom.

    Rolling resistance would be awesome too (not to keep giving you things to do).
    - Noah Podolefsky -
    The GSX-E

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    Electric Warrior CaptainKlapton's Avatar
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    I am already working on it Noah
    I am also close to having an algorithm for determining the CdA value based on the dyno plot and top speed, that way we can get reasonable values for bikes which haven't been tested. I also found an empirically determined formula for rolling resistance which is working very well so far.

    I will get all that stuff up once I do some more testing on it.
    "Never let schooling interfere with your education."
    -Mark Twain

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  8. #6
    Seņor Member podolefsky's Avatar
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    I shoulda figured. Awesome work.
    - Noah Podolefsky -
    The GSX-E

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  10. #7
    Member robermelendez's Avatar
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    This is awesome! I love the push for more simulation!

    I look fwd to seeing your rolling resistance estimates, I don't know of a good source for motorcycles on that.

    "Bicycling Science" by D.G. Wilson has some pretty good numbers for bicycles, but I don't know of a similar source for motorcycles.

  11. #8
    Electric Warrior CaptainKlapton's Avatar
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    Uptate & Rolling Resistance Calculations

    I have now added a section to the original post for average values as well as filled the missing values from the wind tunnel tests with calculated ones.
    I found that for a faired street bike the CdA increases by ~22.6% when upright vs. tucked. This value was also used to estimate the crouched CdA's for the dual sports for lack of a better estimate. It should be noted that a bike optimized for aerodynamics, such as the 125 and 250cc GP bikes, suffers a much greater increase in CdA(~43.8%) than the road legal counterparts. However, I have also read that the ZX-14 has less buffeting than the Hayabusa when upright, but has slightly higher drag while crouched. So there is clearly a tradeoff between having low drag while crouched or while upright.

    The rolling resistance estimates I have been using came from here. From what I can tell, this formula is quite accurate. I have been using the assumption that the front and rear tires have the same Crr so that I don't have to know the weight distribution and can just put the full weight of the bike on one tire and get pretty much the same result.
    In case you don't feel like looking at the book, the formulas are:

    Pow = (2.36*V*10^-6 + (4.88*V*10^-6)/p + (4.41*10^-10)*(V^3)/p)*N, for velocities 165kph and lower

    Pow = (4.88*V*10^-6)/p + (8.09*10^-10)*(V^3)/p)*N, for velocities above 165kph
    Pow = power consumed by rolling resistance in Kw
    p = tire pressure in Bar
    V = velocity in km/hr
    N = vertical Newton load on tire

    They also have a plot for the Crr vs. velocity up to 150kph at various tire pressures
    CrrPlot.jpg

    I have one more tire model paper I have yet to get through (it's 84 pages of dynamics calculations) but I will see if I can find the link again and will post it here.
    I am still working on finding a way to estimate the CdA of a motorcycle in general, but it is only a matter of time.
    "Never let schooling interfere with your education."
    -Mark Twain

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