LMP2 physic bugs

Discussion in 'Bug Reports' started by Stefan_L_01, Jun 28, 2020.

  1. Stefan_L_01

    Stefan_L_01 Registered

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    I played around with the lmp2 and found some weired behaviour that are imo bugs.
    So here you go.
    First is about the front ARB. I went on a track that is a "0" shape, 2 straights, 2 180° turns. Packer were 0. First test was with full ARB on front and rear. The top chart shows the suspension stiffness which shows in the turn during cornering the increase of the ARB, else the normal spring stiffness. The topchart uses F_Srping / Pos_spring as formula.
    As you can see with full ARB (lmp_maxarb.png) the increase in front stiffness is at least twice as high as for the rear but ok. The problem is when I do same test with unmounted ARB, both front and rear. The rear shows a linear behaviour, so it goes with standard springs as expected (suspension travel matches force), but the front shows still a VERY HIGH non-linearity cornering. Actually this increase in stiffness (again: front ARB setting UNMOUNTED) is still WAY higher than the increase in stiffness for the rear with ARB setting at 5 of first test!!!

    Next issue in next posting
     

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  2. Stefan_L_01

    Stefan_L_01 Registered

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    Ok issue 2:
    I tested the lmp2 on a straight (high downforce, long gear setting), and put the packer in a way that I can get 310km/h approx. This is the lmp2_LowRideHeight.png, again 310km/h. You can see the initial ride height on the outer left when v= 0
    Then I increased the ride height (and only the ride height!) by 15mm both front and rear. As consequence, the final ride height at high speed is less for the rear (!!), I´m bottoning out and the resulting top speed is only 300km/h !!! Check the cursor pos, the cursor values are to the left: For low ride height I´m at 26-27mm, for high ride height at 20, both at their topspeed, and topspeed for highrideheight is even 10km/h lower btw).
    The safe ride height not to touch ground is probably around 25mm btw.

    Its clearly a bug imo that with a given packer setting more ride height will make you bottoming out. This is also very noteworthy in the daytona oval (daytona endurance) where more ride height will make you touch the floor more easily!! clearly a bug!!

    Sidenote: does the 3rd spring packer has any effect????
     

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    Last edited: Jun 28, 2020
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  3. Andrea Terzi

    Andrea Terzi Registered

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    First thing is a big WTF in my opinion, sure a bug or probably they call "detached" something that actually isn't detached.
    Second thing you spotted is instead normal. As you increase ride height using the same packers you will go into packers later than before on straight. But remember tyres still flex as before. So basically you get a stiffer suspension later when your tyre is already more flexed, causing bottomimg down. I hope you will get what i mean
     
  4. Stefan_L_01

    Stefan_L_01 Registered

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    Tire flex is same as tire load is same. Suspension stiffness, packer, they do not change weight nor downforce.
    Note that rear gets lower, front being high. The nose up rake angle reduces downforce, less load actually. And 10kmh less makes up for some less downforce too, more than any tire flex
     
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  5. Andrea Terzi

    Andrea Terzi Registered

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    I know tire flex is the same. What changes is the timing where you engage packers. Increasing height makes you engage packer later on straight, and so you engage them when your tire is more flexed than before (because you are at an higher top speed than before). Because of that you start to have a stiffer suspension from a lower ride height than before, and that causes bottomimg.
    Then talking about front increasing its height i don't know what to say, maybe that is really a bug.
     
  6. Lazza

    Lazza Registered

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    @Stefan_L_01 could 1 be related to bump rubbers? We don't know the ride height they are engaged at.
     
  7. Stefan_L_01

    Stefan_L_01 Registered

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    No because front ride height in the corner (see cursor of unmounted png, values left, I compressed the rh chart but you can read values) is higher for both front left and right than on the straight before entering turn, probably due to engine / rear wheel torque at 250kmh in turn (5th gear) compared to 310 on straight in 6.
    You would see a non-linearity allready on the straight but this isnt the case.
    Btw i could corner quite well with front arb removed and rear on 5 max. On a flat test track at least
     
  8. Stefan_L_01

    Stefan_L_01 Registered

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    No, see again. With higher ride height i get 10kmh less, because I touch ground !! I start touching ground when I set my ride height 15mm higher, or I do not touch ground if I go 15mm lower, sry, you can not explain this to anybody!

    We set a ride height in setup as discussed multiple times, while in reality we would change the mount of the suspension.
    Also while in reality changing ride height would not significantly change the point when the suspension runs into the rubber, as this depends on the suspension travel and not ride height, in rf2 changing ride height WILL change the suspension travel when you run into the rubber. So the internal packer in the physics is adjusted to match allways a minimum rideheight. And the bug probably is that this adjustment calculation is wrong in case of lmp2, it "overcompensates" and gets too low or rubber way too soft somehow
     
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