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Cherrier Vivace & Tograc

Discussion in 'Official Content' started by Falkrum, Feb 12, 2020.

  1. default0.0player

    default0.0player
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    No its NOT. You cannot defy physics, an open diff simply cannot send more torque to one side, the torque distribution is always 50:50. The use of brakes is to reduce one side of the torque and NOT increase the other side torque. Brake cannot send torque.

    Looks like I have to bring that one up again. More information


    Torque Vectoring is currently WIP, according to Diamondback. Update: Now THAT's torque vectoring
     
    #1221 default0.0player, Sep 1, 2020
    Last edited: Sep 1, 2020
  2. Inline6lover26

    Inline6lover26
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    Eh... not true, I read the Tograc/Vivace have an "E-diff", basically its an open differential but it can also "act" as a locked differential in extreme cases such as this one on picture:

    screenshot_2020-09-01_03-36-41.png
    (the tograc can effortlessly climb this ramp with only 2 wheels on perfect contact with the ground on any "drive mode")

    in other cases of traction loss it can send torque to the wheel with most traction via locking the loose wheels with the brakes. (its kinda clumsy, but a lot of new cars do that nowadays).
    or brakes the inside wheel on a turn, sending more power to the outside wheel for better handling through corners, this way its atleast mimicking the effect of torque vectoring.
    (also, EV torque vectoring is really different. as it can virtually control torque almost instantly and correct any kind of traction loss. so, you cant compare both.)

    Also, the FCV seems to have an active AWD system (looking to the "powertrain" app). that means on regular/slow driving (on "comfort" mode) it sends most/all of its power to the front wheels. but on heavy acceleration it can send a bit more power to the rear for a better launch. so no, its not always "50:50" because its not a sunburst lol.

    In conclusion, the Cherrier FCV has "Torque Vectoring via Braking" (or "XDS" as the VAG group calls it on their cars)

    There's an article on carwow about this: https://www.carwow.co.uk/guides/glossary/what-is-torque-vectoring
     
    #1222 Inline6lover26, Sep 1, 2020
    Last edited: Sep 1, 2020
  3. default0.0player

    default0.0player
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    Brake does not send more power to the outside wheel, it does send less power to the inner wheel, though.
    Then again, "Torque vectoring via braking" simply does not exist, this "terminology" is from vehicle scam advertisers, they mislead the phrase "torque vectoring". the "Torque removal via braking" would be more appropriate. The XDS is simply an aggressively tuned traction control.
     
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  4. Diamondback

    Diamondback
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    Where's the popcorn? :D

    In short: Torque Vectoring, as in a technology actively distributing torque in order to help rotating the car around its Z-axis is not in the steam version of the game atm.
    Brake actions are only taken when things are already kinda going wrong (too much speed difference between the shafts of a diff, understeer, etc), brakes are not used in a proactive manner atm.

    Now, as for brakes and open differentials:
    Open differentials always send the same amount of torque to each side, no matter what you do, this is the case.
    The same is not true for power though, just think about it, power is torque * rotational speed, that means when a wheel is standing still (aka rotational speed = 0), it does not translate any power.
    What braking of the faster spinning wheel does is increase the torque being sent to both wheels, so technically it sends "more" torque to the previously too slow wheel, not "more" than the other wheel, but "more" as in "more than before".

    You can use brakes to add a torque around the Z-axis (just brake the inner wheels...), but this is not used as an proactive thing at the moment.
     
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  5. Justy4WDTURBO

    Justy4WDTURBO
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    I wonder if 0.22 will bring us a powertrain visualization app that shows the eDiffs working? @Diamondback
     
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  6. btcb48

    btcb48
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    This is still 1 of my favourite differential resources: https://oppositelock.kinja.com/your-differential-and-how-traction-works-1661277563

    IMHO, sharing my 2 cents, and getting carried away:
    • While the term "Torque vectoring" is becoming too generically applied, not helped by non-critical motoring press, it's still important to assess the operational characteristics and merits of the various types of system regardless of branding.
    • Most "torque vectoring" systems work by differential steering and will proactively brake the inside wheel on turn in (using the steering angle sensor at minimum) to induce yaw.
    • Differential steering via brake can interface with various diff types, XDS and McLaren's "brake-steer", essentially being an extension of their ABD/EDL functions, work with open diffs, PTV pairs with a mechanical LSD, while PTV+ and VAQ work with computer controlled clutch lockup LSDs.
    • As the Cherriers brake in a reactive fashion on inside wheel overspeed and don't activate without gas input, they intentionally act more similarly to the simpler ABD/EDL than XDS.
    • The sharp turn in while on the gas, sometimes only at particular speeds (observed myself at 80 to 100 kph on the 310 DCT), may be caused by the system perhaps over-reacting and rapidly alternating in brake action for both wheels in rapid left-right-left-right-... fluctuation.
    • I suspect that modern IRL systems, integrated with ESP, permit some wheelspeed difference at higher vehicle speeds to prevent this from happening, perhaps when it calculates that optimal ABD intervention (for equal wheelspeed) may aggravate vehicle instability. Recall that ESP still takes various inputs into calculation, even when the interventions are disabled by the driver (ESP-off), so certain extreme code brown incidents can still reactivate the ESP. Older ABD systems pre-ESP generally stopped intervention entirely above 40 to 60 kph, while some sportier systems paired with modern ESP like XDS seem to deactivate around 80 to 100 kph.
    • Actual gearset-based "true" torque vectoring add-ons for open differentials are rarer but can work without brake steering, though I believe that certain systems like the last version of Mitsubishi's AYC in the Evo X had a mode that could activate both geared overspeeding and diff braking at the rear axle without the rest of the stability and engine throttle control intervening. Need to get a translation for that Best Motoring test video...
    • 1 downside of these systems is that they are not actually able to effectively "lock" the differential like a lockable diff or a very, very high lockup and preload tuned clutch LSD. The core differential is still an open type, though not too big a deal as ABD is pretty much a free inclusion with TCS/ESP software. On one hand the Gen 3 Focus RS has no problems, on the other the AYC fitted Evo X struggles on the 1 sided roller tests, could be too weak or absent ABD effect, the Ralliart with the mechanical rear LSD struggles a little less.
    • Don't think there's a modern system like this for FF layouts either, think the last was Honda's ATTS.
    • There may be a misconception going around about just how much factory standard/OEM clutch based mechanical LSDs lockup. High lockup clutch LSDs tend to induce trickier handling characteristics as they force the drive wheels to match speeds no matter what. I believe this is why Porsche force paired fairly low accel (with higher decel) lockup clutch LSDs with the permanent (up to 40 kph) ABD when optioned in manual 993 C2s, and also later made (up to 100 kph) ABD a non-defeat standard feature on all road models with ESP and most water cooled models with TCS regardless of diff type. Porsche mechanical LSDs are also notoriously weak.
    • There's also some reason that Lotus and McLaren are hesitant to make LSDs standard, or even available. And also why most higher end sports cars have switched to computer controlled clutch lockup LSDs; no need to worry about static preload settings or unexpected mechanical force induced lockup, just fine tune lockup based on all the driver and other inputs.
    • ATBs like Torsens have friendlier handling characteristics, especially on front axles, but revert to open behaviour when one side has zero traction. So ABD is still required for ideal consumer grade use, though I guess they are calibrated for reduced braking effect to make use of the bias effect compared to an open diff.
    • Actual locking diffs are heavy and the locking functions cannot be used on grippier terrain. (Take note, Beam 4x4s that spawn with the transfer case engaged.) What Mercedes does on modern Gs is retain the non-defeat (at less than 100-something kph) 4ETS/ABD system with manually switchable lockers that are off by default, so one can still drive hard on tarmac roads with some open diff correcting brake action, at least before the non-defeat ESP intervenes.
     
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  7. olliebob112

    olliebob112
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    Have anyones electric X motors stopped working?
     
  8. default0.0player

    default0.0player
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    Yep, the rear torque vectoring diff on the EVO can work with zero throttle.

    Mechanically-wise the Rear diff of the EVO can lock, if the torque vectoring gear has 10% overdrive, then fully engage the left clutch will make the left wheel always spins faster than the right wheel, and vice versa.
    However it's controlled by AYC, which won't work with zero lateral G and zero steering angle, making the rear diff open on roller tests.
    The same applied to the Outlander, which has a center transfer case(FWD part time AWD) and Active Front Differential. Again the individual rear brake is controlled by AYC which won't work with zero lateral G, making the Outlander unable to pass a single rear wheel on tarmac roller test. NOTE: Not to be confused with Outlander PHEV, this fake AWD even cannot pass the front wheel roller, rear wheel on tarmac test.

    That's my article written half a year ago.
    Looks like it might be necessary to emphasize energy efficiency, I'll update it when I have sufficient free time

    OT:

    The FCV currently has two problem with the AWD system.
    1 The braking is too slow. When you hit the gas the engine will vroom first and the vehicle understeer because of the inner wheelspin, then about 200ms to 500ms the inner wheels brake.
    BeamNGdrive-019009934.png
    2 The center clutch locking is too high at low throttle, leading to driveline wind up.
    Note the inner rear wheel is faster than the inner front wheel, which wears down tires much faster IRL.
    BeamNGdrive-019009934-RELEASE-x642020_4_1211_06_29.png
     
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  9. G-Farce

    G-Farce
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    Hol up. Just hol up

    Are you saying there is a version that already has torque vectoring?

    ....Where do i sign up
     
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  10. CaptainZoll

    CaptainZoll
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    as in in the dev's internal WIP biulds of the game, it'll probably be in 0.21.
     
  11. btcb48

    btcb48
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    The dev Vivace torque vectoring vid is below for those interested.

    https://beamng.com/threads/development-media.24313/page-4#post-1183947

    While not too realistic to have a true TVD at both ends for a factory variant, it would be neat to keep the parts as a high cost or bonus unlock item in career mode. A bit like how GT2 (unrealistically, TBH) handled the special TCS tuning item.

    There are various issues with Mitsubishi's takes stuffed into the spoiler box:

    The Evo's AYC does take wheel speed into consideration, and split mu performance improvements are cited in official documents, but it does not physically lock or have preload. Maybe the lower friction of the 2 surfaces tested was more like sand or gravel instead of ice, a roller, or air?

    From my understanding in terms of torque across the diff, AYC is able to bias a multiple of it to 1 output like a sort of selective Torsen with added overspeed effect, but sharing the same worst case "zero traction at one output" problem.

    The TBR isn't 1:1, but isn't infinite either as there's no physical coupling ability between both outputs of the diff. Hence the conventional clutch rear LSD Ralliart (or Evo RS) can perform better on the diagonal test at least, though it does not quite lockup sufficiently to pass the "1 rear wheel" test.

    While AYC's take on the TVD system is great for agility on the move without touching the brakes, from a worst case traction perspective, some improvement would be needed if the exact same implementation was still produced today against modern rivals.

    ABD should instead intervene at low speed, at least when ESP (ASC) is still on, with less engine side throttling from TCS. Stronger ABD coupled with the front helical type should in theory show benefits during the "1 front wheel" test.

    With these 1 output slip scenarios, it is also unclear if newer TVD systems like the Twinster can strongly direct torque to the other side without ABD intervention.

    The conventional FWD based systems in the SUVs (and possibly the one in the regular Lancer) are able to pass the 3 roller test if the remaining wheel with traction is at the front, even without the V6 model's front active LSD.

    The Eclipse Cross is able to inconsistently pass the "1 rear wheel" test if the combination of settings is correct. There is some rear ABD effect with the later model years of Outlander, just that the final result is insufficient for 3 roller tests like with some older Haldex Audis.

    The newer model years of the PHEV can pass 2 roller tests, though the ABD effect is still too weak for 3 rollers. The traction management between the non-mechanically linked front and rear drivetrain is too conservative, passing the "both front" or "both rear" roller tests require the virtual centre lock to be engaged and ESP (motor throttling) to be turned off.

    On differentials too:

    While TBDs/LSDs are more efficient in power transmission while limiting slip in fast, hard driving compared to a plain ABD implementation, one also has to consider the intended use of the vehicle as a whole.

    Engineering for mass consumer usage is ultimately a compromise between cost, maintenance, user friendliness, the pros and cons for the most common intended use and all that jazz.

    Remember that the whole point of a regular open differential is to allow easy differences in driven wheel speed especially in tight manoeuvres.

    Common showroom grade clutch type LSDs have the interfering preload and don't lock completely, 40% seems to be the common limit. Their roles are ultimately compromised between allowing steering or traction depending on driven wheels and the inputs of gas or brake at that moment.

    TBDs experience issues when 1 side lacks traction entirely.

    And with everyday usage, is a typical car owner more likely to experience a severe split mu condition when moving off from a stationary position or when driving like he stole it? (Neither where I live, TBH)

    Of course, a powerful sports car designed for consistent fast lap times and race grade endurance with a conventional suspension setup would do well with a TBD/LSD or an active type. Or a high powered FF hot hatch, since overheating the front brakes from ABD intervention isn't the best idea.

    Any modern RWD BMW with any type of slip limiting diff is more capable at fast driving and drifting than 1 with an open type, both have ABD anyway, but who are the most common BMW owners today?
    It's more likely that the most exciting thing the car will ever experience is the owner's pubescent kid sneaking it out to the abandoned lot to do donuts, which ABD still does a decent job of supplying. Bonus is that a cheapskate can be more easily convinced to change all 4 brake pads at the same time.

    Something used for slower, more utilitarian, and severely low traction use could be better served by a switchable diff locker, while an economy car with a careful owner will unlikely be driven in such a manner where the higher speed gains (and monetary costs) of a TBD/LSD will bring significant benefit over an open type with just ABD.

    And if one drives an economy car hard and fast enough on public roads to necessitate a dedicated slip limiting diff type, energy transmission efficiency doesn't seem to be a priority.

    Whichever diff type though, ABD is a minor add on to modern ABS and can supplement or even be a temporary substitute if the slip limiting or locking mechanism wears out excessively or fails entirely. It can also be calibrated to only work at specific wheel RPM ranges to avoid excess intrusion. Poor, ineffective implementations are getting less and less common too.

    To sum up, choosing a front or rear differential type is all about picking the best compromise for intended usage.
     
    #1231 btcb48, Sep 3, 2020
    Last edited: Sep 3, 2020
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  12. -LeveQ-

    -LeveQ-
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    I'd rather an electronically controlled mechanical LSD :p
     
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  13. G-Farce

    G-Farce
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    Oh yeah If I had my rig setup again, on the wheel I'd love that but on a pad... seems like it's vectoring territory! Plus it's always good to push the boundaries of technology. Speaking of pushing the boundaries of tech...Nvidia...you have made this year somewhat decent!
     
  14. default0.0player

    default0.0player
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    I found that none of them have two-step
     
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  15. Justy4WDTURBO

    Justy4WDTURBO
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    Bug report: half-shafts on AWD Togracs somehow move independently from the transfer case.
     
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  16. default0.0player

    default0.0player
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    I found two ESC problem in the FCV
    1. No or little braking when understeer. No matter the steering wheel you turned. This problem is relatively minor
    BeamNGdrive-0202010611-RELEASE-x642020_9_712_33_40.png

    A even bigger problem is the ESC often misinterpret (False Positive) oversteering on low-friction surfaces. Often brake the WRONG wheel, making handling terrible
    BeamNGdrive-0202010611-RELEASE-x642020_9_712_33_00.png
    As shown, the vehicle is understeering but the ESC brakes the outer front, making the vehicle understeer even more.
     
  17. P_enta

    P_enta
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    I mean if youre trying to rally a stock economy hatchback irl it would probably do the same so
     
  18. default0.0player

    default0.0player
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    Not just rally it, What I meant is putting the vehicle on dirt is very easy to replicate the same problem. The problem is the ESC is misleading, I have this problem multiple times that the ESC act against oversteer when the vehicle is actually understeer. I put the dirt driving screenshot as if rallying only because it's easy to replicate the problem
     
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  19. BeamNG.Lover2002

    BeamNG.Lover2002
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    It is true that it should brake the front left instead of the front right in your circumstance but take any Vivace and accelerate to 50mph and throw the car in a wild zig zag and you will see the car brakes the correct wheel in this circumstance to correct the oversteer. I understand this system is meant to reduce understeer but maybe it is more safety orientated then we think
     
  20. default0.0player

    default0.0player
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    If your guess is correct, the ESC cannot differentiate zigzagging or a single turn, so it's tuned to brake the outer front in sufficient speed and high steering angle, regardless the vehicle is actually understeering or oversteering.
    Excuse me, is "safety orientated" is to slide straight out of the road in a tangent line and crash onto anyting off the road? In #1236 the second screenshot's case, the front right wheel has the most weight on it, braking this very wheel will hurt cornering the most, which is the worst thing any ESC can do.
     
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