[SOLVED] Spreadsheet - Gear, Tyre, Diff, Engine, Oh My

Discussion in 'Car Modding' started by thoraxe, Jun 30, 2018.

  1. thoraxe

    thoraxe Registered

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    So, I'm having a little trouble with the engine tabs on the spreadsheet. I have a dyno chart for my engine (essentially a Toyota 2JZ 3.0L motor) which gives me HP and Torque vs. RPM. I know what transmission I'm putting in and have the ratios. I know what my rear end ratio is. I know what tire I'm targeting. But I'll be damned if I can figure out what to put in any of these boxes. Let's ignore all the crazy mixture and turbo stuff for now.

    Here's the current version of my spreadsheet:
    https://www.dropbox.com/s/xdtt8ro7gbhf84v/rF2-Physics-Calculator-jzz30-V0.33-v0.4-180630.ods?dl=0

    Dyno chart:
    https://www.dropbox.com/s/9fozumdfbkq5gfh/sc300-dyno-rpm.jpg?dl=0

    Gear ratios:
    2.66, 1.78, 1.30, 1:1, .80, .62

    Final drive: 4.08

    Tire: https://www.maxxis.com/catalog/tire-450-107-victra-rc-1 (275/35R18)

    Looking at the Studio 397 spreadsheet the speed-in-gear seems all jacked up. Here's a speed-in-gear chart:

    https://docs.google.com/spreadsheets/d/1Ow-ruaHPm8TvzEthwMJKfgtS8847rJlL_YXCUBehshI/edit?usp=sharing

    Here are the values from the spreadsheet:
    92.15
    137.61
    189.88
    245.73
    307.16
    393.16

    I am thinking that my issue is all in the final drive. I'm trying to understand the "bevel" times "combined". Or perhaps those values are in metric. But they are basically 2x what the Google spreadsheet indicates I should expect. I can't believe this factor of 2 for everything is magic, and 1KPH is 0.62 MPH, so that's not it.

    Any thoughts here?
     
  2. thoraxe

    thoraxe Registered

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    This looks... odd.
     

    Attached Files:

  3. thoraxe

    thoraxe Registered

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    OK, I mostly figured it out. I switched to the tires from the NGTC BMW (TBC+TGM). Their TGM looks like it's basically the "released" Dunlop race tire TGM. As for the TBC, the spreadsheet doesn't really do much TBC "calculation", so whatever for now.

    I took a look at the Skip Barber driveline settings and figured out that the gear settings correlate to "positions" in the gears file. Here's the new relevant driveline section:

    Code:
    GearFile="JZZ30_Gears.ini"
    AllowGearingChanges=0
    AllowFinalDriveChanges=0
    AllowReverseAndNeutral=(1,1)
    ForwardGears=6
    FinalDriveSetting=1
    ReverseSetting=7
    Gear1Setting=1
    Gear2Setting=2
    Gear3Setting=3
    Gear4Setting=4
    Gear5Setting=5
    Gear6Setting=6
    
    And here's my gears.ini now:

    Code:
    [GEAR_RATIOS]
    Ratio=(12,32) // 2.667
    Ratio=(14,25) // 1.786
    Ratio=(17,22) // 1.294
    Ratio=(20,20) // 1.00
    Ratio=(25,20) // 0.800
    Ratio=(32,20) // 0.625
    Ratio=(13,38) // 2.923 (reverse)
    
    [FINAL_DRIVE]
    Bevel=(1,1)
    Ratio=(13,53) // 4.077
    
    I still feel like it's an annoying bug in the UI that:
    1. It shows the teeth count instead of the gear ratio
    2. It shows the calculated final ratio as opposed to the actual gear ratio

    If you look at the picture I uploaded above, as an example:

    It shows the bevel and final ratios of 16/24 (1.5) and 13/53 (4.077). Which is actually wrong (I fixed this above in my new gearfile) as I wanted 4.077 final but the spreadsheet basically doesn't let you get there.

    Then, it shows 12/32 for first gear (which is actually 2.66666), and then shows the product of the gear and the final (1.5*4.077*2.6666 = 16.30).

    I don't know about you, but I'm an actual racer and when I look at that screen it makes no sense to me.
     

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