1.04 update - Physics changes - Your impressions?

Discussion in 'Gran Turismo 6' started by SillyBillyP, Jan 28, 2014.

  1. OdeFinn

    OdeFinn

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  2. Morphisor

    Morphisor

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    Forgive the late-ish response, but I couldn't find this video till now (forgot that the name for these things is moose test..).

    Pretty much exactly what you requested :)



    Now keep in mind that the average sports car will show less extreme behaviour, but especially if you increase tire grip, it is still very similar.
     
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  3. andryush

    andryush

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    That's fabulous :D
     
  4. focusST300

    focusST300

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    All these cars are already known for bad behavior on "moose test" (and not only there.. )

    But you don't expect this to happen to a GT-R R35 ..even with rs tires. Am not say it's impossible to happen.. I say ..every time i try to turn at Scwedenkreuz (ring) (and without hitting the kerb), the car tends to became a ....van ..

    Try these settings.. ‘Ring / Gt r v spec ’09 / weight reduction(everything) only / rs tires / no aids / abs 1
     
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  5. Thatswackson

    Thatswackson

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    Thanks for the detailed pictures and explaintions. The car I was using was the opera s2000 I think, which while not a race car, have a very low center of gravity and tuned and lowered suspension. But thanks again.

    What I was simply saying, and using your diagrams for reference, is tires on the ground fighting the forces of physics being applied do not have the available grip to stop from slidding the the direction of the vehicle. Essentially this leads to a outward slide by the two wheels in contact with the ground where eventually all tires end up back on the ground. There are exceptions to this, its possible to get popped up past the point of no return or balance point like we called it on bikes and from there, its only quick steering or luck I guess that would save you. Looking at your diagram you see that the tires contact patch is slightly reduced, not as much as your pics show because the tires will compress and there is probaby some negative camber from the set up and suspension compression. Anyway, im just thinking out load now. Your physics are right and I understand the roll point of a vehicle and the center of gravity. Cheers. Ill stop rambling now.
     
  6. Sander 001

    Sander 001

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    Well I requested cars, not utility vehicles. All these have high centers of gravity and some with very narrow tracks and have been known to flip for decades. The strange thing is, I haven't seen these kinds of vehicles go on 2 wheels in GT6 nearly as often as NSX's, Lambos, Ferraris etc.
     
  7. eran0004

    eran0004

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    The grip is probably reduced when the tyres are at an angle, but the forces acting against them are also reduced, because when you're turning while the car is tilting, body mass isn't acting on the tyres to the same degree as they are when the car is flat on the ground.

    Imagine if you have a tree that you want to pull down. You have a truck with a winch. If you attach the winch to the bottom of the tree, it's going to be hard for to pull it down, because the opposing force from the roots will be acting very near the force from the winch. Unless the soil is loose or the roots are bad, the tree is probably not going to go anywhere.

    Attach the winch further up, and the same force that you used in the first attempt will be able to pull it down (unless the tree breaks of course, but let's imagine it's made of something really strong).
    tree.jpg

    In the first attempt, the winch attempted to move the roots sideway. We can translate that to the body mass of a car with a low center of gravity attempting to move the tyres sideway when cornering.

    In the second attempt, there'll be next to no sideways forces trying to move the roots, instead most of it is used to rotate the tree. That can be translated to the case where the center of gravity has shifted further up. The body mass (the winch) isn't going to try and move the wheels (the roots), it's going to attempt to rotate the entire car (tree).
     
  8. Gentoo64

    Gentoo64

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    Try a standard NSX S Zero with stock suspension, and countless other cars. Rolls on almost every corner on Nordschleife don't even need to touch the kerbs.
     
  9. Boone

    Boone

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    I drove an NSX Type S Zero on Ascari (stock) during the Super Lap and it did not roll. I have yet to roll a car in game without hitting a curb, and yes, even on the Nordschleife.
     
  10. andryush

    andryush

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    You win. I didn't tried it with SL55 AMG but i tuned V12 Vantage instead, it behaves similar to SL 55 due to heavy weight. Stiffening front spring for about 10-20% harder than rear spring helped a lot! Now it understeers a little only in high speed turns. I'll try setting front RH a little higher than rear, front downforce and weight transfer from back of the car should push it to the ground when cornering. Is my thinking correct?

    As for the physics discussion, i would say that cars became more understeer, but maybe it's just coincidnece that this two cars i drive lately are behaving this way.
     
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  11. Morphisor

    Morphisor

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    Yeah, that's definitely worth trying. Do be careful with the differences in RH though, too much difference will have the opposite effect.

    Also, even just lowering RH and increasing springs all around, keeping to the same balance, should be able to significantly decrease chassis movement in any direction. But again, too much will have your car bouncing over every bump it finds.

    Those 2 cars you mention are both heavy front engine RWDs; this kind of sports car almost always has some understeer.
     
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  12. andryush

    andryush

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    What i don't like about GT6 since the beginning is how they recreated losing traction of FF cars when accelerating fast. There's no "jumping wheel" effect which you get when front wheels of FF cars are losing traction in real life. In GT6 wheels just spin with this weeeeeeeeeeeeeeee!!! sound...
     
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  13. 2P0

    2P0

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    Rather than starting a new subject, I thought I would share it with you guys here in new physics thread a few things that bugs me.
    I know there are bigger things to worry about like lack of uniform law of gravity, and it's just me being pedantic, but still...

    1. Has anyone else noticed that when you spin and end up going backwards still being in high forward gear, trying to downshift in order to do reverse j turn kind of maneuver will end up on slowing down, as the gearbox allow you to go down to 1st gear only, while in the same speed range, pushing reverse button (by default triangle) will?

    2. Thing that I've discovered just a couple minutes ago -On perfectly flat piece of tarmac, either using wheel or ds3, when you put in full steering lock, both ways, any car, any platform, in 1st gear, carefully hitting accelerator before you hit just shine below 3 km/h, the car will continue to accelerate up to12 km/h, while heading straight, up to 6km/h
     
  14. jr93alty

    jr93alty

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    I haven't tried #2 but it wouldn't surprise me if true. GT5 had some of the worst low speed physics ever. I thought GT6 fixed some of it but it seems to have regressed recently.
     
  15. OdeFinn

    OdeFinn

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    IRL injection system equipped cars go easily 12kmh after hitting throttle, its injection systems normal behavior, encoded in ECU to raise injection when resistance detected.
     
  16. andryush

    andryush

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    Well, cars normally should go with few km/h when on 1st gear. even without applying throttle. It's because of static engine revs that make engine work and wheels to spin when on gear. If there was no revs at all, engine would stall.
     
  17. OdeFinn

    OdeFinn

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    @andryush, sorry but you're "wrong", like I said earlier, on injection based engines it won't stall. Program inside ECU raise rev few along adding more throttle, not much, but some, depend code/car on each ECU.
    So right and wrong, revs plays in certain area without user interrupt.
    Try on real car: gently raise clutch pedal when 1st gear is on, if car isn't moving and gaining some speed you can contact to workshop and ask them to fix your car. :)
     
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  18. Ridox2JZGTE

    Ridox2JZGTE

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    I tried with a turbo car long ago, even on 2nd gear on a slight incline, gently releasing the clutch, the car slowly creeps up to walking speed, didn't stall, might have to do with the torque.
     
  19. andryush

    andryush

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    I struugle to write correctly in english what i wanted to say, but i wanted to say same thing as you. Car would go on even without applying throttle by driver. Because of that static engine revs i was talking in previous post. To be honest, i never saw a car which would stall when on gear and off throttle when clutch gently raised.
     
    Last edited: Feb 9, 2014
  20. 2P0

    2P0

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    I do understand your point guys, but as far as I can tell, while this is the case of having a manual gearbox and operating the clutch pedal yourself (which is ultra handy in slow traffic, especially in diesel cars) I cannot tell from my own experience, that this is also the case in automatic/semi automatic gearboxes. Anyhow it still feels like an error, if you consider that in a straight line, after reaching 6km/h, the car will start to slow down. If that was done on a purpose, it raises more questions about gearbox mechanics in Gt6.
     
  21. andryush

    andryush

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    In GT6 car slows down completely until it stops or it keeps going few km/h? Gearbox mechanics in GT6 are weak, as i heard, clutch in GT6 works only in ON/OFF mode, no real control over it.
     
  22. brrupsz

    brrupsz

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    I came back to playing GT5. Six is just not for me with current physics. I constantly get mad with how cars behave. MR's like Diablo GT2 or stock NSX are just freaking masochistic to drive. Cobra tuned to the maximum handles just so wrong regardless of tuning.

    By the way - why rallying is so screwed in GT? It's like driving on bumpy asphalt with less grip. Fastest way to go is basically slow driving, no powersliding. I mean what is the point of having 4WD in this situation?
     
  23. TenEightyOne

    TenEightyOne

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    Correct, but saying that "body mass isn't acting on the tyres to the same degree as they are when the car is flat on the ground" is incorrect.

    We're actually applying the lateral force to all points of the tree (in the displayed plane) equally. We know that the top of the tree will bend before the roots give way but eventually the roots will move. This will be as a result of the momentum of the vehicle's mass exceeding the lateral grip of the tyres against the surface.

    We can alter the proportions or severity of movement by suspending the wheels and absorbing as much of the sprung mass's movement as possible but ultimately all we're doing is affecting the way the body mass's inertia reacts against the direction of travel and against its own suspension.

    Body mass never stops acting on the tyres unless you're airborne :)
     
  24. f1webberfan

    f1webberfan

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    What do you mean by power sliding?
     
  25. jr93alty

    jr93alty

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    I imagine he means turning in early and 4 wheel drifting under throttle like rally drivers actually do to maintain the cars momentum and exit faster.
     
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  26. LazyJK

    LazyJK

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    Part of the problem might be that fact that tire grip on loose surfaces comes from something different than grip on hard sufraces. On gravel and snow the tire grips by cutting the top of the surface and digging in, you can basically 'lean' against snow/gravel by digging into it: when you slide the grip actually increases. I cannot feel it in GT, plus it has a very strange feeling of the brakes 'sticking': you let go of the brake before a turn but the car just plows forward and you need to use throttle to rotate it into the turn.
     
  27. eran0004

    eran0004

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    What I meant is that the tyres have a certain amount of friction - force - and force is required to accelerate a mass. The greater the mass, the more force is required. In a lightweight car, the tyres might be able to accelerate the car up to 2G, while in a heavy car the same tyres might only be able to accelerate it up to 1G.

    When the car is leaning on two wheels, the mass that the tyres need to accelerate when they turn is less than when the car is flat on the ground, because when it's leaning most of the mass can "escape" over the tyres while when it's flat on the ground the mass can't do that (unless you're driving a high center of gravity narrow track death trap). With a significantly lower mass to accelerate, the same tires might be able to pull up to 4G (I'm just making numbers up here, so don't build a space rocket based on these calculations).

    Of course the amount of friction is probably reduced a lot when the car is leaning, but I've never seen anyone skid on two wheels so the remaining friction is probably more than enough to make the car roll over.


    tiltforce.png
     
  28. TenEightyOne

    TenEightyOne

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    I'm sorry but that's utterly incorrect.

    I think you might be talking about the resistance of the tyres in the lateral axis, but your terminology is mostly incorrect.

    The lateral grip of a tyre (compromised in any instance by existing lontitudinal forces) is a function of the reaction between the surface of the tyre against the land's mu in any horizontal plane.

    The grip is affected by how hard the tyre is being pushed away from the car's body towards the road, the mu of the surface, any existing forces acting on the tyre's surface, the pressure of the tyre, the heat of the tyre and so on.

    The vehicle's accelerative forces are limited by this grip, they are not a function of it.
     
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  29. ITCC_Andrew

    ITCC_Andrew (Banned)

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    I recently had an epiphany when testing rally setups in GT6, after discussing the setups with the local rally shop/rally team. (They operate about 3 km. Away from my house)


    Every setting I changed - according to what they had told me they do with their rally cars - lowered my stage times/lap times etc. By about a tenth of a second every time.


    It all felt realistic, I could feel the changes as I made them, and the lap times and consistency showed it.


    I have limited rally experience, having attended rally events, driven rally stages, and rallycross. I have an event coming in March, as well. My real life car (Impreza 2.5RS wagon) has two viscous limited slip differentials. Although they are dim-witted and slow-to-respond, they are very, very effective in controlling the car. However, modern purpose-built rally cars have two electronic LSDs, which are quite clearly faster to respond, meaning that the car can be driven with more confidence, since the electric signal travels at the speed of electricity, which is much less than a tenth of a second, versus the human reaction times of between 0.3 seconds (in some trained professionals) to 1 second or more, and the 0.7 second response time of the viscous LSDs. I can feel the higher response time of the v. LSDs, and the low response time of e. LSDs. This is astonishing! The fact that I can toss my GT6 replica of my real life car into a corner and anticipate the exact amount of grip available throughout the entire corner on gravel and snow ahead of the corner is simply astonishing! I can feel the way the v. LSDs respond and it's nearly exact.


    The suspension tuning is very, very accurate. The weight distribution is wrong, but decent. The tires have good grip, and it feels somewhat accurate (though I wish GT6 had non-spiked winter snow tires, as those are the only tires legal for competition in Canada, except in Québec, so that's what I'm used to.) If they fix the physics below 20 km/h, and the weight distribution, the physics will be almost spot-on.
     
  30. eran0004

    eran0004

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    No it's not incorrect. Look at the following two figures:

    center3.png
    Point A is the contact between the tyre and the road - that's where the friction is acting.
    COM is the center of mass of the car.

    In figure 1 the car is flat on the ground and turning right. The friction between the tyre and the road is applying a force of 2 to the car. The kinetic energy of the mass is opposing that force by a force of 1. COM is higher up than point A, so the forces aren't pointing perfectly straight at each other, but the forces aren't great enough to make the car flip over (there's still the force of gravity pulling the car down). As the force of point A is greater than the force of COM, the COM will go where point A is going and it will be accelerated in that direction by a force of 1 (2-1).

    In figure 2 the car has come up on two wheels (hit a curb or something at high speed) and is still turning right. The forces are the same just to keep things simple. Now there's a greater difference in height between point A and COM. As a result, when the car is turning, the opposing force acting from COM is not acting against it, it acts at a higher plane. As a result, when point A moves to the right, accelerated by a force of 2 (2-0), COM moves to the left, accelerated by a force of 1 (1-0).

    In the first figure, when the two forces are acting against each other, they both can't go where they want to go. They will cancel out each other and whoever is stronger will win.

    In the second figure, when the two forces aren't acting against each other, they can both go where they want and as a result the car will flip over.

    If this was incorrect, then how does a car flip?