Downforce and Drag - HDV editing

Discussion in 'Car Modding' started by SL1DE, Nov 28, 2017.

  1. SL1DE

    SL1DE Registered

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    Does increasing drag also increase downforce in this? I know in real life they're two separate things...

    I need to increase the drag on the straights but also decrease the downforce in the corners. I have weight and power correct, but the car is just too fast. So I feel like perhaps the aero needs adjusting.

    Anybody know what changes I should make to the HDV?
     
  2. Lazza

    Lazza Registered

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    Drag is called drag, downforce is negative lift.

    In each of the main body sections ([FRONTWING], [REARWING], [LEFTFENDER], [RIGHTFENDER], [BODYAERO]) you will find parameters defining drag and lift for those parts. For BODYAERO the drag is 'hidden' as the middle value of BodyFore=(). So if you're too fast on the straights you can increase that value as a starting point. Wings and fenders may be more or less relevant depending on the car type you're dealing with.

    The various DragParams and LiftParams have the base as the first value. For modest changes you should be fine to just adjust that single value as you see fit. If you made large changes you might need to adjust the other values so that the available range makes more sense with the new base.

    If the car is too fast mainly in high speed corners, then aero might well be the way to go. If it's too fast everywhere, however, or especially at low speed, then you might be better reducing tyre grip in order to slow them down. You'll find base static and sliding grip values in the [REALTIME] section of the .tgm files. Usually best to adjust those together (so both -2%, for example) to avoid changing the feel of the tyres.
     
  3. Lgel

    Lgel Registered

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    May be this can help.
    http://wiki.rfactor.net/index.php?title=Hdv#.5BDIFFUSER.5D
    Cheers.
     
  4. SL1DE

    SL1DE Registered

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    Doesn't really answer my question, just leaves me confused.
     
  5. Lgel

    Lgel Registered

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    Sorry if I confused you.
    If you want to tinker with aero values, it is better that you understand how it works, it is quite easy to mess things.

    To reduce straight line speed simply, you can change this line:
    BodyDragBase=(0.3555) // Base drag to
    BodyDragBase=(0.45) // Base drag

    Cheers.
     
  6. Daniel Surace

    Daniel Surace Registered

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    i think Lazza has pretty much summed it up correctly. there are several values for drag and down force all separate per each component on the car.
    If this is for the 1996 Mod, i did write on steam that it feels like the tyres are way to grippy. But could be some drag values being wrong as the cars did seem like straight line rockets but AI seemed fine so that's debatable. Maybe try finding some footage or speed traps, corner speeds from 1996 season and test some circuits. if its high speed corners your car is miles quicker could be drag and Aero values.

    edit: on further testing and inspections. Drag seems OK from some basic test.
    however looking at the Tyre files it seems the fastest (eg) front tyres has just as much grip as a 2012 pirelli slick.
    Since the AI performance isn't too bad in comparison to real lap times. id be adapting this approach. Compared a 2012 TBC file from the pirelli and the TBC file from the 1996. Work out the percentage different in Lat/long grip and apply the different to the Static baseCoeffience in the TGM files. (6-8%) i think its roughly from my calculations, and work from there.
     
    Last edited: Nov 28, 2017
  7. SL1DE

    SL1DE Registered

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    I was playing with the tyres and reduced some grip to the point where my lap times were equal to the AI's. On mine with the AI on 100% the AI were still getting 1:15's at Interlagos, as well as I. So there I discovered that the issue was with the car itself. The weight was too light and there's too much aero. I mean FISI levels, FISI is based off a 2011/2012 car which has a lot more downforce than a 1996 car. I fixed it so that the average sim racer will get 1:18's (maybe 1:17 if you're good). Now I have been requested to make real car specs available, so I need to learn about this aero stuff.

    Setting it up in 5 tiers.
    1. Williams, Ferrari
    2. Benetton, Jordan, McLaren
    3. Tyrrell, Sauber, Ligier
    4. Minardi, Footwork
    5. Forti

    For 3, 4, and 5, I need less downforce (cornering speed).

    I think I figured it out though, negative "FWLiftParams" (and RW) equals more downforce? That would make sense, more lift = less down. Less lift = more down.

    I already figured out the "drag" thing hours ago.

    Edit: I'm right, it says it right on the rFactor website: "That is -0.6078 for this car. Being negative, this provides downforce."

    Thanks for the link Lgel!
     
    Last edited: Nov 28, 2017
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  8. Daniel Surace

    Daniel Surace Registered

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    Looks like you have a decent understanding. i find a lot of this is trial and error to see the difference some of the settings make. you can read a bit of things for reference and some understanding but until you try in practice its much better.

    Look for mods with comparison levels of lift and drag etc. like CTDP98 or something that was done well. that might give you a reference level perhaps. find a good base that gives you right lap times for your Tier 1. then just work percentages off that for the lower tiers. you will get there.

    Good luck!
     
  9. Raintyre

    Raintyre Registered

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    For example: FWDragParams=(0.5, 0.062, 0.0086)

    This is for the front wing. First value (0.5) is a base drag coefficient, which doesn't depend on front wing setting, while the other values increase drag depending on front wing setting.
    Total front wing drag will be = 0.5 + 0.062*setting + 0.0086*setting^2

    The same thing applies for the rest of aero devices.

    If you change downforce you will also change drag a little bit, depending on your rake angle, but it is a small percentage, almost not noticeble most of the times. Inversely, changing drag you will also change a bit of downforce.


    >>>For BODYAERO the drag is 'hidden' as the middle value of BodyFore=()

    I think middle value is lift. Drag would be third value, but i think it is overridden by BodyDragBase anyway.
     
  10. Lazza

    Lazza Registered

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    Indeed, I said drag in my post for BodyFore, I meant lift.

    *I'm reading too fast, you were quoting my post lol
     

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