ATrac question
- Thread starter Aznwolf118
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I've seen some interesting controlled and scientific tests of traction control, but none demonstrating the effectiveness (or ineffectiveness) of ATRAC when 2 or 3 wheels are slipping.
I'm not the type to take peoples words for things like this unless it's the designers of the system that have tested it and know how it performs. If you do even a little reading on the topic you'll see too many examples of people asserting 'facts' that are completely inaccurate. In my opinion the real problem is that Toyota doesn't publish the details clearly enough. It only gives vague descriptions. Look at Jeep as a prime example of the opposite approach - they have awesome videos and explanations of how each of their traction control systems work. In the absence of detailed information from the manufacturer we end up with interpretations or speculation about how the system does and doesn't work. http://www.jeep.com/en/4x4/how_systems_work/ -> totally cool, wish Toyota did the same.
Anyhow - I'd love to try some split mu or roller tests if anyone has access to these materials or access to a good location for the tests etc.
Basically I'd envision two types of test - split (2 wheels slipping) and 3 wheels slipping. I can think of at least 3 ways to do this - either using wet basalt (or some other similar material) on an uphill slope, rollers (flat ground should suffice), or getting the slipping wheels in the air (probably not a good idea unless it's an airbag or something that's lifting).
PM me if you have any interest or ideas.
- Art
I'm not the type to take peoples words for things like this unless it's the designers of the system that have tested it and know how it performs. If you do even a little reading on the topic you'll see too many examples of people asserting 'facts' that are completely inaccurate. In my opinion the real problem is that Toyota doesn't publish the details clearly enough. It only gives vague descriptions. Look at Jeep as a prime example of the opposite approach - they have awesome videos and explanations of how each of their traction control systems work. In the absence of detailed information from the manufacturer we end up with interpretations or speculation about how the system does and doesn't work. http://www.jeep.com/en/4x4/how_systems_work/ -> totally cool, wish Toyota did the same.
Anyhow - I'd love to try some split mu or roller tests if anyone has access to these materials or access to a good location for the tests etc.
Basically I'd envision two types of test - split (2 wheels slipping) and 3 wheels slipping. I can think of at least 3 ways to do this - either using wet basalt (or some other similar material) on an uphill slope, rollers (flat ground should suffice), or getting the slipping wheels in the air (probably not a good idea unless it's an airbag or something that's lifting).
PM me if you have any interest or ideas.
- Art
I give up! In time you will learn more about the system. I only have 10-years experience with it. Maybe you have more.
No worries, no need to get defensive, no need to respond further if you're not interested.
I'm just trying to be objective and take a scientific approach.
I'm not claiming to know more than anyone else. My source for information is Mr. T himself - I'm not making anything up - just quoting actual Toyota Documentation - in my book you can't get better than that except for real world testing.
Mr. T's documentation does not indicate the limitations you claim and you provide no source for your assertions.
Mr. T does specify that L and H and RPM effect the way the ATRAC works by design. Mr. T does indicate that ATRAC senses speed at all four wheels and that it can apply brake pressure at up to 3 wheels at the same time.
Shotts, agaisin,
I actually like where you guys are taking this. Having both of you firmly on opposite ground but yet willing to prove your position means we'll get more data for this experiment. Please keep up the good fight and hey maybe ...
if either of you, or both, can document a way to test your ideas (theories) and post on Mud with in a procedural doc, maybe Mudders can print the docs and then take them out on the next excursion. If they video the "tests" then maybe we can have a video center documenting the several ways to use, not use, ATRAC. And maybe with enough of these we can actually understand the system better.
Right now, I feel like Shotts really knows his stuff from behind the wheel when in the thick of jungle. But that doesn't help me, or other Mudders. Some more discussions, a procedural approach to testing, some videos, etc would.
And if that's too much hassles, then maybe Shotts can come to Cali and just learn me somefin.
I actually like where you guys are taking this. Having both of you firmly on opposite ground but yet willing to prove your position means we'll get more data for this experiment. Please keep up the good fight and hey maybe ...
if either of you, or both, can document a way to test your ideas (theories) and post on Mud with in a procedural doc, maybe Mudders can print the docs and then take them out on the next excursion. If they video the "tests" then maybe we can have a video center documenting the several ways to use, not use, ATRAC. And maybe with enough of these we can actually understand the system better.
Right now, I feel like Shotts really knows his stuff from behind the wheel when in the thick of jungle. But that doesn't help me, or other Mudders. Some more discussions, a procedural approach to testing, some videos, etc would.
And if that's too much hassles, then maybe Shotts can come to Cali and just learn me somefin.
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You will read this NOWHERE.
Toyota "sells" A-TRAC as a comparable replacement for locking F/R differentials and for the vast majority of LC owners, the LC's A-TRAC performance lives up to the expectations set by their sales and marketing people. Sales and Marketing mumbo-jumbo aside, dissected or otherwise (e.g. There is probably a reason why they say "the wheel" rather than "a wheel"), there are plenty of discussions here with real-world examples of where and when A-TRAC is enough and where and when front and/or rear lockers are desirable.
I think there are generally two camps of A-TRAC equipped owners that have opted for f/r lockers... the "better safe than sorry" folks and the "I'll never wish I would have had lockers again" folks. I'm in neither camp and I've found A-TRAC to be sufficient for my (relatively modest) off-road exploits, but Shotts' explanations, vids, etc. seem to foot with how my A-TRAC behaves.
I think there are generally two camps of A-TRAC equipped owners that have opted for f/r lockers... the "better safe than sorry" folks and the "I'll never wish I would have had lockers again" folks. I'm in neither camp and I've found A-TRAC to be sufficient for my (relatively modest) off-road exploits, but Shotts' explanations, vids, etc. seem to foot with how my A-TRAC behaves.
ShottsUZJ100 said:
i read it here:
"It independantly controls the brake hydraulic pressure to the four wheels in accordance with the extent of the slippage at the wheels, as detected by the Skid Control ECU."
This much is clear - there's one skid control ECU getting speed signals from four wheels and capable of braking independently at four wheels - it's verbatim from their documentation and is visible in their system diagrams showing the solenoid valves (SA1, SA2, SA3, STR). If it's only capable of applying brakes to one wheel per axle or at most two wheels, the excerpts I quoted would be patently false (and based on other examples I've seen in the toyota documentation they are careful enough to point out those sorts of 'notes' or limitations in the design).
At this point it can go in circles since Toyota does does make specific claims or have specific enough examples. Short of more detailed design specifications, only real life (at least pseudo scientific) testing will be the final word (for me personally).
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A-trac demo video (albeit on a Tundra)
I'm not sure if Toyota changed the Atrac programming logic between the 100 series and its newer trucks but this video shows a Tundra with Atrac sending some power to one wheel with traction:
How A-trac works‏ - YouTube
This video may be more applicable to a 200 series based on the fact this is a 2009 Tundra.
I'm not sure if Toyota changed the Atrac programming logic between the 100 series and its newer trucks but this video shows a Tundra with Atrac sending some power to one wheel with traction:
How A-trac works‏ - YouTube
This video may be more applicable to a 200 series based on the fact this is a 2009 Tundra.
FnA - that's what I was looking for. Very cool.
I fully recognize real world and controlled environments can be different - even if it works in that controlled environment, in the real world there might not be enough traction (and/or torque) for long enough at one wheel to move the vehicle up a steep incline in all conditions etc. However, assuming there's nothing but ATRAC on the vehicle, it does show that even with 3 wheels spinning, ATRAC is capable of putting enough power to the one wheel with traction to move it (on flat ground).
Only problem I have is that I don't know the vehicle's specs, settings, and it's not an LC100/LX470 so perhaps it has a different flavor of ATRAC implemented? While I have found differences b/w flavors of ATRAC over the years as I list below (from 94 through 2003+), I haven't found any that lead me to believe a 2000 is less capable of overcoming the scenario in the video, and certainly a 2003-2007 LC/LX would appear to have all the latest improvements in ATRAC. (I will try to do more research there).
If I can get my hands on 3 of those rollers I'd gladly try it out. With CDL engaged/disengaged, in 4L, 4H, RPMs < 3000, RPMs > 3000, etc.
Thanks for digging that up and posting!!!!
More on the topic of potential differences b/w implementations, here's what I've been able to find on Toyota University and TIS (although none seem to be fundamental differences):
-- TRAC vs. ATRAC - depending on where you look in Toyota's documentation TRAC is sometimes distinguished from ATRAC as TRAC for 2WD and ATRAC for 4WD/AWD but the same principles apply, only difference is how many drive wheels and the fact that with ATRAC there's different behavior depending on the transfer case range and RPMs. But the concept of applying brakes to minimize wheel slippage and distribute power to wheel(s) with traction is the same.
-- In 2003+ LC/LXs, there are the following changes:
1) the deceleration sensor that is provided for the brake control system (ABS with EBD, Brake Assist, A-TRAC, and VSC system) has been integrated in the yaw rate sensor
2) Information on the steering angle, vehicle speed, and the actual turning angle of the wheels can now be exchanged between the skid control ecu and the vgrs ecu, which has been newly added for the VGRS
3) By changing the resistance value of the coil of the solenoid valves in the hydraulic brake booster esatblished in A-TRAC as shown in the following table, the heat resistance has been improved. As a result, the consecutive operation time of this system has increased.
-- in 2006+ LC/LXs: "Along with the use of the CAN (Controller Area Network), the Translate ECU is added between the Skid Control ECU and the ECM. The Translate ECU converts between different communication protocols of serial signals and CAN signals for communication." Looks like it changes communication b/w ECUs, but not the fundamentals of ATRAC behavior.
-- Some vehicles allow you to disable TRAC/ATRAC, some don't.
-- In the case of the FJ, in earlier years, TRAC and rear locker wouldn't work together without a hack (in other words by locking the rear ATRAC was disabled).
-- in a pre 2000 document describing TRAC design, one of the technical documents explains the differences b/w supra and camry/avalon's trac systems. (Supra Turbo had it in 94 and Camry/Avalon had it in 97. "Although the Supra and Camry/Avalon TRAC systems both control engine torque and drive wheel braking, how that is accomplished varies and therefore both systems are covered separately in this section." From that point on (years/models) I did not see such a distinction in the TRAC implementations but it could be that one would have to dissect the design section for each model to see the differences, just never saw any summary like that for other model implementations).
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YOU ARE MAKING UP WORDS! NOWHERE WILL YOU READ THAT IT WILL APPLY 3 BRAKES AT ONE TIME!
Nice try with the video. Double loser though here. First, the writing at the opening reads correctly...within the given axle.
Second...it shows nothing! You need to see what all 4 wheels are doing at the same time. The two rears had zero traction so they would just alternate spinning. The front had one wheel with traction and it was excellent on-hard-surface traction. So when that tire got power the thing moved. Never would you see 3 wheels not moving...only two...if the video had a quad-view of each wheel...it does not.
Keep telling yourselves this guys. In your trucks you'll NEVER experience it. Quit theorizing and go run tests on your own trucks.
Bottom line: ATRAC is like a really good LSD, but not a substitute for lockers. It will get you 90% of the way, but at the end of the day there are situations where ATRAC can't pull you out even if you have two wheels with some degree of traction.
Adding lockers to an ATRAC vehicle is the best of both worlds; you can get further than a completely open system before locking yet have the security of being able to lock when truly needed. Plus by locking the center and rear you have improved steering response without added drivetrain stress.
The argument was one of semantics; John's point was that the 100 can't direct 100% of available torque to a single wheel. He's correct in this. My point is that the fact that it's spinning other wheels is irrelevant as long as it's giving torque to the wheel with traction, which is not possible without a front or rear locker (or both).
Adding lockers to an ATRAC vehicle is the best of both worlds; you can get further than a completely open system before locking yet have the security of being able to lock when truly needed. Plus by locking the center and rear you have improved steering response without added drivetrain stress.
The argument was one of semantics; John's point was that the 100 can't direct 100% of available torque to a single wheel. He's correct in this. My point is that the fact that it's spinning other wheels is irrelevant as long as it's giving torque to the wheel with traction, which is not possible without a front or rear locker (or both).
If the center diff was locked I agree. If the center diff was not locked (i.e. opne) you're incorrect - we know the other 3 were on rollers so by definition if center diff is open one of those 3 spinning wheels would get the drive force instead of the one with traction. Isn't that 4x4 101 and indisputable?
So yes, the video could be disputed if you tell me that the cdl was locked (in which case the front axle is all that mattered in the video).
However, please answer me this: in the same test using our LC/LXs if the CDL is open and it moves the vehicle with only 1 wheel getting traction and the other 3 on rollers, then do you agree that we have proof that the system is capable of transferring drive force to only 1 wheel with traction? And that's only possible by braking the other 3 wheels at the same time?
I'll agree as I have in multiple posts that even if it works in a controlled environment that it still might not work in all real world conditions.
I think the question here is on ATRAC capabilities and in my view of things, in order to start that conversation logically you need to first know how the system was designed and what it does in ideal conditions, then you can talk about why it might not always work in real world conditions.
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I wasn't really trying to make a point one way or the other, just providing information. Regardless of whether there is a camera for each wheel, I would assume that since 3 of the 4 wheels were on rollers and had "zero" traction power was sent to the fourth wheel that did have traction moving the truck forward. Would it work as well if the fourth wheel was in mud or sand or in an off-camber situation, probably not.
I agree that the ATrac with Rear Locker was best combination of traction and maneuverability on any trails I did in FJC. That is what I would do in the 100 as well when money permits....for now though, ATRAC has done everything I have asked it east of the Mississippi where other vehicles with lockers treaded. Proper technique and throttle I say would get you through all but the MOST DEMANDING obstacles. Most people dont know how to effectively use their ATRAC and avoid holding a steady throttle and let the system do its magic.
I really dont care of one wheel can get 100% of power to it....all I care is that it gets enough to get me moving and I can get the other wheels working as well.
I do know that my ATRAC in 100 works better than it did in my FJC....or seems more robust in its actions.
I really dont care of one wheel can get 100% of power to it....all I care is that it gets enough to get me moving and I can get the other wheels working as well.
I do know that my ATRAC in 100 works better than it did in my FJC....or seems more robust in its actions.
I wasn't really trying to make a point one way or the other, just providing information. Regardless of whether there is a camera for each wheel, I would assume that since 3 of the 4 wheels were on rollers and had "zero" traction power was sent to the fourth wheel that did have traction moving the truck forward. Would it work as well if the fourth wheel was in mud or sand or in an off-camber situation, probably not.
What you don't see on the video is there is another tire on the rear axle spinning as well because ATRAC can only brake 2 wheels at a given time.
This is the key info the video does not show.
You're just not getting it and I am not a good enough writer. Sorry on this.
Oh, and "4X4 101" says that a 4WD vehicle is really only a 2WD vehicle unless it has locking differentials. Wait...maybe that's advanced "4X4 102".
No doubt and I don't disagree at all. At the end of the day the truck moves forward with only one wheel having traction. As was mentioned above ATRAC + rear locker is the best but ATRAC by itself is extremely capable.
You're dodging the question - if CDL is open with 3 wheels slipping and only one wheel getting traction, do you agree that the only way for the vehicle to move forward is ATRAC braking on the other 3 at the same time?
I'm just trying to be logical here.