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Need help with rally suspension damping setup

Discussion in 'Troubleshooting: Bugs, Questions and Support' started by ahza2496, May 15, 2020.

  1. ahza2496

    ahza2496
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    Joined:
    Nov 18, 2017
    Messages:
    7
    Hello,

    I'm trying to make the Sunburst rally to closely mimic the Subaru Impreza WRC2004 but im having trouble with the suspension setup.

    -I already made a boxer 2.0 engine with a torque curve that closely resembles the WRC engine
    -tried porting the vivace rally suspension into the sunburst but i found out that the suspension is too advanced and the travel is too high for a WRC2004 car(the wheels are too far down when the car is midair).
    -tried to make the bumpstops have high damping values while that worked a bit, it causes the suspension to break when landing 80% of the time.



    Take a look at this WRC2004 onboard video, the jumps are at 2:12 and 3:20, where at big jumps the car is stabilizes almost immediately after landing, i cant replicate that in beamng, the car will always soft rebound or land gracefully due to high damping rates.

    My problem is that most sizeable jumps make the car bottom out(despite the hydraulic bump stop added) and bounce back if the suspension is too soft but too stiff will cause it to be undriveable throughout the track.

    Any recommendations?

    Also, if anyone has information on the spring rates, damping values and damping knee velocities for the Subaru WRC2004 car would be helpful.
     
  2. xiao_zhi_zhu

    xiao_zhi_zhu
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    Joined:
    Apr 13, 2020
    Messages:
    1
  3. atv_123

    atv_123
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    Joined:
    Aug 5, 2012
    Messages:
    1,289
    Well, I don't know if your going to end up finding anything about the settings that actual rally cars use... mostly because most teams like to hold their cards to their chest so that other teams can't use the information they have to get a possible advantage... that and spring and damping rates literally change on these cars from race to race... Heck... sometimes even stage to stage.

    That all being said, I can at least give some tips that might help with your tuning.

    Your mostly looking to control jumps, so let's start with that bit of info and work from there.

    Ride Height - naturally if jumps were your only concern, you would want your ride height to be as high as possible... this usually isn't the case though, so your going to instead want your ride height to be as high as possible without A. Maxing your suspension travel just sitting still B. High as you can go while not compromising your weight transfer control by your sway bars C. As high as possible without allowing your suspension to max out in travel through corners. Once your suspension starts to hit max travel, you start to lose body control of your car, so naturally you would want to try to avoid maxing out your suspension travel while all your tires are still on the ground... or accidentally picking your tires up off the ground... that also doesn't help. I would suggest about +15% ride height over a stock car as a start point.

    Spring Rate - this actually goes for most cars... including some higher forms of racing (Formula 1 and other high downforce racing are the exception to this rule). Your spring rate should only be just high enough to hold your car at your set ground clearance while sitting still... nothing more. You don't want to control your car through your spring rate, you want to control it through your damping which you have much more control and adjustability over.

    Bump Damping - This is basically the damping that your suspension uses when it initially hits a bump... so basically the suspension under compression. This is going to be fairly stiff... mostly to absorb the large jumps that you want to account for. As you stated, you want to try to not bottom out your car, so this should be high enough to absorb the largest jump in the stage so that it just touches the bump stops on your suspension... nothing more. Now if you have the ability to, sometimes you can adjust both low and high speed Bump Damping... use this to your advantage to have softer damping for normal driving and stiffer damping for absorbing the jumps. The softer the damping, the more traction you will have when your wheels are still on the ground... the stiffer the damping, the less traction, but more control... keep that in mind.

    Rebound Damping - This is basically the damping that your suspension uses to recover its normal ride height after a bump. Now, after rebounding from a jump, your going to want the Rebound Damping to be fairly stiff as well. This is because you don't want your car to bounce back up after a landing, you want it to gently stand back up so you can control the vehicle. Again, if you have the option, you want your high speed damping to be fairly stiff for jumps, and your low speed damping to be much softer to control your vehicle when all the tires are still on the ground. Less damping, more traction, more damping, more control, but less traction.

    I can talk about sway bars if you want, but for landing jumps only, you would want your car to be under control side to side, so medium to stiff sway bars should do the trick in that department.

    Edit: Almost forgot...

    Toe - Toe values will help keep the car pointing in the direction your intending... since you want the car to keep tracking straight, increasing the tow in (bringing the fronts of the tires closer together) in both the front and rear will help with straight line stability. Note, this will reduce turn in in corners. I suggest no more than 2° toe in on the rear and no more than 1° toe in on the front if not just leaving it completely straight.

    Camber - Camber really won't play a huge role in landing jumps (unless your running some extreme angles or something) so I would just set this up as you normally would for maximizing corners. Granted... the settings that would give you the largest contact patch on landing would be the best for landing jumps technically (so 0°F 0°R) however anything up to 3 or 4° really shouldn't throw that off too much.
     
    #3 atv_123, Jun 29, 2020
    Last edited: Jun 29, 2020
  4. ahza2496

    ahza2496
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    Joined:
    Nov 18, 2017
    Messages:
    7
    Thank you for the suggestions and apologies for the late response.

    Xiao_zhi_zhu,

    I've tried your car and its pretty good at jumping just not with bumpy tracks, maybe good for track smooth rally tracks like American Road. The suspension is too stiff for typical rally tracks that I use.

    atv_123,

    For now I've been using suspension values (Spring Rates, Anti Roll Bar) from DiRT Rally and DiRT 4, but I still couldn't find any values about damping. For the suspension itself I transplanted the Vivace rally suspension into the sunburst rally suspension to have the maximum travel to compensate for the weak hydraulic bumpstop.

    The problem I'm having is the car bounces back after landing a jump, unlike in the video. I'm finding a way to make it so the car can have reasonably soft suspension to handle bumps while having enough rebound damping(settles as early as possible) for jumps.

    Ride Height I always set maximum with Spring Rates minimum enough to hold the car up as you said, but I do have problems with damping. I'm currently tinkering with high/low speed damping (compression and rebound) and the damping knee but I still cant find the balance.
    Do take note that I am able to set the suspension values far beyond the limit since I'm adjusting through the car files itself.

    About the sway bars, I just kept it at minimum or no sway bars at all since anything above 10NM would rock the car side to side during bumpy power slide (Possibly because the way I set up the car)

    For the camber and toe settings, I just go with 0 unless I need to correct any understeering or oversteering issues.

    Would you suggest to have higher rebound than compression or otherwise? Also where do I put the high values? should I have a high slow compression or high fast compression damping?
    Do you have any information about the bumpstop damping as well? that would be useful
     
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