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Auto LSD

Discussion in '2nd Gen. Tacomas (2005-2015)' started by Thelt, Sep 26, 2012.

  1. Oct 4, 2012 at 8:07 AM
    #81
    GP3

    GP3 Well-Known Member

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    This is the only proof I've seen. It doesn't mention 4wd though.

    Untitled.jpg

    This one mentions 4wd.

    ToyotaDriveModes-1.jpg
     
  2. Oct 4, 2012 at 8:11 AM
    #82
    shemp

    shemp Well-Known Member

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    No, VSC is the exact same system.

    TRAC *is* ALSD *is* ATRAC. Effectively just different names for the same thing.

    Nobody cares what you want to CALL the modes, the IMPORTANT part is what they each DO.

    VSC (ALSD+engine regulation = default mode)
    ALSD (like VSC without engine regulation = tap button)
    OFF (open differential = hold button)

    Now you want to quibble about when the thing is making use of the sideways sensor, be my guest. It quite frankly does not apply to this discussion.

    Because its turned off, obviously.

    Because its turned off, obviously.

    VSC most definitely includes a traction control mode.
     
  3. Oct 4, 2012 at 8:12 AM
    #83
    DoorDing

    DoorDing Intentionally obtuse

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    Thanks!

    The footnotes indicate that even disabled, VSC is waiting in the wings. That might be a problem on a performance car at the track, but at least on paper, I think that's a good approach for a 4WD truck.
     
  4. Oct 4, 2012 at 8:18 AM
    #84
    GP3

    GP3 Well-Known Member

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    Nope.

    Vehicle Stability Control ≠ Traction Control

    I agree (being that they are traction controls), but making up different names like you do below, is not going to help anyone understand Toyota's system.

    You are using my argument against me? You are right. VSC does not belong in this conversation.

    You just contradicted yourself in this post.
     
  5. Oct 4, 2012 at 8:26 AM
    #85
    shemp

    shemp Well-Known Member

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    VSC == NO QUESTION AT ALL == TRACTION CONTROL.

    "LSD" is an industry standard LIMITED SLIP DIFFERENTIAL.

    TRAC/ATRAC/whatever are extra made-up nonsense names. Understanding the system involves ignoring all the contradictions that Toyota has introduced in the names of the different modes. What they call ALSD in 2wd is *IDENTICAL* to what they call TRAC in 4wd. If that isn't confusing, I don't know what is.

    MY use of VSC in this discussion is EXCLUSIVELY related to the TRACTION CONTROL features that correspond to THAT MODE.

    When the vehicle is in VSC ****MODE****, it is operating ALSD with ENGINE REGULATION.

    YOU are the one focused on how it responds to the yaw sensor. NOBODY CARES ABOUT THAT ASPECT OF IT.

    No. A light is just a light.

    You asked why the light was off. I answered: BECAUSE THE LIGHT IS OFF.
     
  6. Oct 4, 2012 at 8:28 AM
    #86
    OZ-T

    OZ-T Thats what it is to be a slave ...

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    VSC and Traction Control seem to indeed be 2 seperate things in my experience
     
  7. Oct 4, 2012 at 8:33 AM
    #87
    shemp

    shemp Well-Known Member

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    When the buttons are pressed such that VSC would operate, i.e., in "VSC MODE", will it or will it not operate ALSD+engine regulation on a slippery surface?

    Whether or not yaw sensor triggers a different routine in the firmware, when it is in that MODE, it will operate ALSD+engine regulation.

    For the sake of SIMPLICITY, that MODE is best referred to as "VSC", for lack of a better name.
     
  8. Oct 4, 2012 at 8:39 AM
    #88
    DoorDing

    DoorDing Intentionally obtuse

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    I'm certain VSC and ATRAC do have some effect on each other; they have to, since they utilize the same systems to accomplish their task. My guess is that VSC can override ATRAC output, since the overall stability of the vehicle should be more important than any single wheel's available traction. The main difference is that ATRAC doesn't use yaw data, while VSC obviously does.

    I understand why Shemp prefers dumping ATRAC/TRAC naming for LSD. My issue with that is that is all the e-diff solutions are a bastardization of what a true, mechanical LSD really is, even if the end result is similar (at least until the brakes overheat). Toyota would do well to pick one name and stick with it. Since they offer a mechanical LSD in some models, I believe it'd be best to reserve any use of LSD for that differential, and only use TRAC for open differentials that are being controlled via brake modulation. A-LSD is the worst of both worlds, since it's not an LSD, and it's a needless duplication of TRAC on an open differential.
     
  9. Oct 4, 2012 at 8:40 AM
    #89
    GP3

    GP3 Well-Known Member

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    Ok I'm not going to waste my time any more. We must be getting trolled. I forgot you are the same guy that is an expert on Tacoma transfer cases.

    http://www.tacomaworld.com/forum/2nd-gen-tacomas/241380-twin-stick-transfer-case-3.html#post5759613
     
  10. Oct 4, 2012 at 8:51 AM
    #90
    shemp

    shemp Well-Known Member

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    The operation of "VSC" (yaw sensor routine) works like this;

    1) you are driving around a corner and the back end starts to kick out.
    2) yaw sensor reading exceeds expected value calculated and/or wheel speed sensors inconsistent with each other.
    3) selective activation of brakes and reduction in engine power output in order to match wheel speeds to the road and reduce kick out.

    When you are in that same mode on a sheet of ice;
    1) You step on the gas and one wheel begins spinning.
    2) Wheel speed sensors inconsistent with each other.
    3) selective activation of brakes and reduction in engine power output in order to match speeds of all wheels to each other.

    Imagine that. Both in the yaw sensor kickout scenario and in the stuck scenario, in BOTH circumstances, it considers relative wheel speeds, reduces engine power and selectively applies brakes in order to match all of the wheel speeds together. The difference is only that in one scenario it also considers the yaw sensor. Think maybe there is less difference between these two scenarios than initial assumptions suggest?
     
  11. Oct 4, 2012 at 8:56 AM
    #91
    OZ-T

    OZ-T Thats what it is to be a slave ...

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  12. Oct 4, 2012 at 10:29 AM
    #92
    shemp

    shemp Well-Known Member

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    I don't agree that ALSD is any kind of "bastardization". The system has more strengths over mechanical LSD than it has weaknesses.

    It also doesn't help for clarity to limit the use of the term "LSD". There is no model of Tacoma offered with an old fashioned mechanical LSD unit any more. They were only available up to 2008 MY.

    In fact, ALSD and LSD are a lot more similar than you would initially imagine. The mechanical differential used a series of friction disks (brakes) to control the motion of the two wheels relative to each other. If one started moving significantly faster than the other, the disks would engage to some degree and slow down the faster moving wheel relative to the slower moving wheel.

    With ALSD, it uses the main brakes to slow down the faster moving wheel relative to the axle housing.

    On a superficial level, ALSD might seem to be less efficient than a purely mechanical LSD. It might leave the impression that energy is taken away by the brakes. That, however, isn't really the case. Imagine that you're stuck with one wheel spinning and the other stationary. 100% of the energy produced by the engine is being lost in the friction between that moving wheel and the ground, yet you aren't moving. If you fully lock that spinning wheel, then 100% of that energy is directed to the opposite wheel. If you 50% lock it, 50% of the energy is directed to the opposite wheel, and 50% is lost as friction to the ground. Yes, of course a slipping brake is going to absorb some energy as heat, but the same thing is happening in a purely mechanical LSD.

    So a more thorough analysis suggests that ALSD is no less efficient than a purely mechanical LSD on an energy utilization basis.

    Next up is efficiency of activation. A mechanical LSD requires a certain minimum amount of slip in order to lock the plates together. ALSD also requires a certain minimum amount of slip in order to know to activate the brakes. Meaning, of course, that BOTH need to actually slip in order to respond. I don't see any advantage for either in this respect.

    Up to here, everything between LSD and ALSD seems to be about equal. There are, however, some noteworthy differences;

    First up is cooling. Suggestion of ALSD overheating and ceasing to react. As far as I can tell, this is predominantly affecting models with the electro-hydraulic brake boosters (ATRAC -- TRD offroad). It is the brake booster itself that overheats, rather than the brakes (which don't have temperature sensors). The models with vacuum boosters have a similar glitch, but not quite the same; loss of vacuum. The vacuum booster can only run the brakes so much before running out of vacuum.

    Now obviously, a mechanical LSD won't suffer those downsides.

    The big downside to a mechanical LSD is what happens when you wear out the disks. It is a bit more involved of a repair to replace worn out LSD disks than brake shoes.

    ALSD has additional advantages over mechanical LSD: that it can be controlled electronically, so can relate front to rear wheel speed, and can be activated in circumstances like yaw sensor.

    The biggest advantage that ALSD has over mechanical LSD is that it can operate on the FRONT in 4wd.

    And last, of course, ALSD can be deactivated. Mechanical LSD cannot.
     
  13. Oct 4, 2012 at 4:57 PM
    #93
    DoorDing

    DoorDing Intentionally obtuse

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    Thanks for your comparison of LSD and ALSD.

    Your list of differences goes to the heart of my point: they aren't the same thing, and at least for me, "ALSD" is a needlessly confusing term. Bastardization may have been too strong a term, but I still think it's a mistake to conflate a computer controlled, brake centric system with a mechanical LSD. ATRAC is a valuable system that can stand on its merits. There's no need for Toyota to glom onto LSD in an attempt to boost its credibility.
     
  14. Oct 5, 2012 at 5:01 AM
    #94
    shemp

    shemp Well-Known Member

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    The big difference, though, is that people understand what LSD *means*. That is the biggest reason to hang on to that term exclusively, and drop the extras.

    TRAC = ALSD,
    ATRAC = ALSD with electro-hydraulic booster.

    ?

    I, personally, prefer the acronyms to actually mean something.
     
  15. Oct 5, 2012 at 5:07 AM
    #95
    DoorDing

    DoorDing Intentionally obtuse

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    Toyota could possibly satisfy both of us by standardizing on ATRAC in all vehicles, driven by an electro-hydraulic booster. Then there'd be no variation in what ATRAC meant, and LSD could be reserved for what it actually is, not what ATRAC simulates. I see it as two sides of the same coin, and I don't think Toyota will clean up this mess in the near future.
     
  16. Oct 5, 2012 at 7:35 AM
    #96
    shemp

    shemp Well-Known Member

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    Well whatever they do, it would be nice if they would at LEAST be consistent, although I prefer to not have the electro-hydraulic booster. Its an extra point of failure and additional expense that wouldn't benefit my use.
     
  17. Jun 16, 2014 at 9:34 AM
    #97
    DoorDing

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    Enough variations of ABS & e-locker override modifications exists that it'd be best to make sure everyone is talking about the same thing. I suggest you find the thread with the instructions that you followed, and post your question there.
     
  18. Jun 16, 2014 at 4:47 PM
    #98
    DoorDing

    DoorDing Intentionally obtuse

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