Spreadsheet Aero units

Discussion in 'Car Modding' started by doddynco, May 21, 2022.

  1. doddynco

    doddynco Registered

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    In the Aero section of the spreadsheet, there is little calculator for coefficient of drag. It looks like this:

    Frontal Area 1.17
    Drag Cd 0.4815
    Cda 0.563355
    ISI 0.3451


    My question is firstly, what is 'ISI'?

    And most importantly, do the spreadsheet entries expect coefficient of drag/area or this 'ISI' unit?
     
  2. davehenrie

    davehenrie Registered

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    lol, that 'might' be the ISI fudge factor....
     
  3. Robin Pansar

    Robin Pansar Member

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    I think that specific section you are looking at is not useful. The ISI/rF2 coefficient is essentially just CLA( or CDA) * (0.5 * 1.225).

    The values you put in for the aero calcs are in rF2 coefficients.
     
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  4. doddynco

    doddynco Registered

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    Thank you Robin. So I'm going to assume 1.225 is the density of air in kg/m3? What does CLA stand for?
     
    Last edited: May 21, 2022
  5. Robin Pansar

    Robin Pansar Member

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    Yes, it's static 1.225 kg/m³. You can set specific conditions via upgrades where you simulate a different air density, but it's a bit clunky.

    You are right, it's Lift Coeff x Surface Area [m²]. I meant more if you just want to convert a value to ISI, but then again maybe just taking CL will be better. Testing both approaches is always viable.
     
  6. doddynco

    doddynco Registered

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    That cleared it up for me cheers. So I think I understand it as Cd/a * 0.6125 = drag.
     

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