4WD, Lock Button, VSC Off Button and DAC Button - How They Work - Page 3 - Toyota RAV4 Forums
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post #21 of 29 (permalink) Old 02-19-2014, 11:17 AM
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Originally Posted by Dr. Dyno View Post
DVS is correct on post #15. The front differential has no mechanism for locking itself and thus sending equal speed to each wheel. From the ABS sensors it does know each wheel's speed. Auto LSD brakes the wheel that's spinning faster.

Traction control on 4WD does the same thing on the rear wheels also. So it has Auto-LSD on both ends. During my getting-stuck tests I've heard the heavy almost disconcerting thumping noises the ABS makes on whatever wheels are spinning. Then if the Skid Control ECU doesn't see the vehicle moving it essentially gives up and takes the throttle away from the driver. Turning TRAC off allows the driver to spin the wheels w/o traction until he either gets unstuck or breaks something.

What I don't know is does Auto-LSD also have the ability to reduce throttle when it sees no movement? And does turning it off allow spinning the tire with the least traction? I do know that when I got my FWD Accord "stuck" with both front tires on ice, both were slowly spinning with my foot to the floor. So it must have some sort of auto-LSD but I never heard any thumping.
I thought the trac button was same as LSD button. But doesn't the 2wd also have a trac button?
Dr J
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post #22 of 29 (permalink) Old 02-19-2014, 11:22 AM
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I don't even bother watching staged promotional videos, especially unrealistic situation ones.
They're like when someone with a Harley claims he has some high HP number. I say, "Okay let's see it on MY dyno." I've seen it be true once in 15 years. (I tested that bike for the editor of American Iron Magazine. He was doing an article but didn't believe the builder's dyno numbers. He confirmed it on my and a third dyno. All three agreed within measurement error.)
I was planning on going with a 2008 forester turbo manual. But ended up going with rav4. During my subaru research, it turns out they do not have front LSD. Yes they can send up to 50% power to the front wheel but it's an open diff. Sounds ok for the average city commute, but won't work in tough stuff, I noticed in those videos they always have 1 rear wheel with traction. I don't know about current Subaru.

That being said, I can't wait to take delivery of my 4.3 and find a willing suby owner who wants to try and get stuck with me!
Dr J
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post #23 of 29 (permalink) Old 02-19-2014, 12:25 PM
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I thought the trac button was same as LSD button. But doesn't the 2wd also have a trac button?
Dr J
We don't have any 2WDs around here but I know one guy in Texas who has two.
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post #24 of 29 (permalink) Old 02-19-2014, 12:37 PM
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I was planning on going with a 2008 forester turbo manual. But ended up going with rav4. During my subaru research, it turns out they do not have front LSD. Yes they can send up to 50% power to the front wheel but it's an open diff. Sounds ok for the average city commute, but won't work in tough stuff, I noticed in those videos they always have 1 rear wheel with traction. I don't know about current Subaru.

Dr J
Yeah, it was a big letdown to watch one front and one rear wheel spinning when I got my mom's supposedly invincible symmetrical AWD 2007 Legacy hung up on a snow drift in PA a couple of years ago. According to the sales flyer I looked at later we'd apparently bought the non-invincible model.
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post #25 of 29 (permalink) Old 02-20-2014, 01:07 AM
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For the sake of conversation, let's discuss the opposite of all this traction stuff. I'm a grip driver. I like Willow Springs and Streets of Willow. Let's say I want a track day with my 4WD. What settings to use? The only 1 I can think of is launching with 4WD LOCK. All the other nannies should be turned off?

Can/will the 4.3 pitch into a corner with inside wheel lifting, doing a 3-wheel dance around turns?

Dr J
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post #26 of 29 (permalink) Old 02-20-2014, 10:00 AM
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Can/will the 4.3 pitch into a corner with inside wheel lifting, doing a 3-wheel dance around turns?
Dr J
Yeah probably could.

Then 2 wheels.

Then 0 wheels.
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post #27 of 29 (permalink) Old 02-20-2014, 02:06 PM
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Buy a car if you want to track? The Rav isn't really agile...at all. (my other car is a mazdaspeed 3)
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post #28 of 29 (permalink) Old 10-20-2015, 07:27 PM
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Ditto SomeGuy - the tracks I've been on won't even allow a high vehicle like the RAV
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post #29 of 29 (permalink) Old 01-04-2016, 11:43 PM
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RE DAC if you have it:

Using this function is something like drinking Absinthe or maybe Yeni Raki. An acquired taste. Scary at first and then with practice, it's still scary. On slight icy hills perhaps it works flawlessly but on the steep hill I come up and down daily (200' in 2/10 of a mile) it can be frightening, even though it has worked every time and gotten me down every time. The hardest part is letting the nanny do the work without interference. Faith in a Nanny is difficult to come by.

The system depends on two cooperating factors: Engine braking (you have to be in L or in first gear or reverse) and your ABS which kicks in about 3mpj/5kph. It is not a constant function so there is this sensation of picking up speed and then the ABS kicks in, chatters and then goes off as you slow and of course the car speeds up a bit again. Your natural reaction when looking down that icy hill is to jump on the brake, but that kills the system, and if there is ice under the snow, Mach speeds are a definite possibility by the next stop sign.

So. In a word. Practice on bare road surfaces until you have a semblance of faith in the system and then you'll still build up a nervous sweat as you look down at what feels like certain impending doom. But it does work. Or it has so far on both snow over ice and a long muddy slip and slide down a sloppy forest road.
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