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http://216.219.239.199/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=18&t=000008
I also tried to explain the 4WD a little better!
* On the 4WD models, the transaxle, front and center differentials, and the transfer unit are all integrated into one unit. This is a full-time 4WD system so power is transferred to all 4 wheels all of the time for optimum stability and traction. In addition, the center differential is a viscous coupling unit that provides a limited slip effect when distributing power between the front and rear wheels. For additional traction, a helical-type, torque sensing limited-slip rear differential is optional on 4 WD models in some areas.
Also, on 4WD models, the propeller shaft is a 4-joint, 3-shaft type. A cross groove-type constant-velocity joint (CVJ) is used for the number three joint to help reduce noise and vibration. A center bearing is also provided to further reduce noise and vibration.
Dianne
I'm not in the market for Highlander, but I thought I pass this along to those who live in OC.
I just bought a Chevy Impala LS. So far, I think the Impala is a better car then a Camry. Time will tell.
That said, I had made up my mind a while ago that I would not buy another vehicle that didn't have, or was expected to get the highest category grade in both the NHTSA and IIHS crash tests (some might say I'm compromising with the "expected" part and they may have a point -- but IIHS/NHTSA doesn't crash test fast enough!). The Highlander (and MDX, ML320, RX300) would fit that personal requirement, but not the Pathfinder/QX4/GM SUV's.
Yikes! I see that body-on-frame sure didn't help the crash test results of those GM SUV's. At least the chest and foot were reasonably well-protected, even though the expected head injuries were comparatively massive (sarcasm intended).
I have not driven a Highlander yet, but I know that the MDX has significant road/wind noise for a near $40k vehicle. Honda/Acura vehicles tend to have worse NVH performace compared to Toyota/Lexus. However, you should test this theory for yourself.
Anyone else try this approach?
Wally
We really want a vehicle that will last us more than the standard US made 50,000 mile and your done.
Thanks
Allow me to explain. The HL has a limited slip center differential. This means that power is split 50-50 unless one end of the vehicle is slipping. If that happens, power is biased toward the end of the vehicle with more traction. It had been my understanding that if you got the VSC, you also got traction control (TRACS). This didn't make sense to me because TRACS applies brakes to slipping wheels which would fool the center differential into keeping power to the end with the least traction.
Now, on to an experiment I did on Thursday. We had about 3 inches of snow which is enough to shut down the world in suburban Washington DC. I took two HLs to the back of the parking lot. One had VSC, the other didn't. From a standing start, I mashed the gas pedal to the floor. Both took off like a rocket. The one without VSC had some side to side fish tailing. The one with VSC tracked very straight.
The part that surprised me was that there was no straight line braking nor reduction in RPMs from the one with VSC. This is what one would expect to feel under these circumstances if it had traction control. I didn't feel it at all and no warning lights flashed on the dash.
This actually makes sense on this kind of 4WD system. It just goes against what I had been told from two different sources. It seems that the VSC on a 4WD (I know the 4x2 must have TRACS), is only to handle later skids. If anybody has more experience with this, I'd love to hear about it.
But because VSC has all the necessary intelligence/components to fully modulate any wheel, TRACS is actually a subset of VSC. So if you get VSC, you have TRACS. And VSC will help in ALL road conditions, you don't need snow to justify it.
LexusSafety.com has explanations.
In my opinion, anybody who doesn't get VSC (if available) is simply saving some dollars at possible expense of their life. But hey, everybody has different priorities.
TC
What I do know something about is the cabin size. I am 6'-3" and turning in a leased Explorer.
You will find the HL MUCH roomier than the Explorer. The leg room is very generous (I do not place the seat back as far as it will go). In addition, the dash is recessed yielding even more room. Most surprising, is the room in the rear seat. I am very impressed with the vehicle. Not just "satisfied," no more, impressed with the fit, finish, power and ride.
Happy motoring.
Steve, the traction control works by monitoring the speed that each individual wheel is spinning. If one wheel is spinning faster than another by x mph, the traction control then thinks that it is spinning and brakes it. It is conceivable that since you started off on a service with equal mu (read: friction co-efficient), all wheels spun at about the same rate, and hence A-TRAC did not see the need to cut in.
Do you think you could find a spot with unequal amounts of traction on each side of the vehicle (split-mu surface?) Perhaps half on snow, and half on gravel (preferably on an unhill slope)? Or simply shovel away about 2-3 car lengths of snow under the left or ride side wheels. I bet the traction control will cut in if you try the same thing.
"...because VSC has all the necessary intelligence/components to fully modulate any wheel, TRACS is actually a subset of VSC. So if you get VSC, you have TRACS."
Tony: Yes! That's precisely right! I'm glad you got it since so many people (including some auto journalists) have trouble with this concept. :-)
Drew
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P.S. I'm a lover, not a fighter, but the guidance systems in a Cruise missle are simply unreal. Topographic and other maps are downloaded into it's on board computers before it is launched. The thing can be launched over a 100 miles away from it's target and it will literally "hug" the terrain while navigating towards its end destination, twisting and turning as necessary to avoid obstructions.
The reason I bring it up is that pieces of the technologies that go into these missles can be used to eventually design "auto-drive" and safer cars.
I've mentioned before that I don't understand how TRACS can work with a center LSD. This experiment seems to confirm they don't.
One other point here, TRACS and VSC are not the same thing. TRACS uses the ABS sensors to detect when one wheel is slipping more than the others. VSC detects lateral skid by other sensors including steering wheel position sensors. These systems work well together in the Sequoia, Runner and Land Cruiser but it escapes me how it can work with a center differential that is a limited slip variety.
You have all the facts straight, yet you don't seem to see the forest through the trees.
No one claims they are the same. But the sensors and equipment used by TRACS is a subset of the equpiment used by VSC. You are exactly right with your breakdown of the stuff. TRACS uses wheel sensors (to detect speed differentials between wheels) and 4-channel ABS to individual pulse-brake (downward modulate) a wheel to correct for "sensed" loss of traction. VSC (as you pointed out) uses yaw (angle direction) sensors, plus steering wheel sensors, and engine throttle control. In order to correct a cars trajectory, it needs to make a decision based on individual wheel speed (the TRACS wheel sensors), yaw, and the steering wheel position. It will then adjust overall engine speed (upward or downward) and individually brake wheels (the 4-channel ABS) as necessary to correct the cars angle, not necessarily its traction this time. A human being can't possibly individually brake any of 4 wheels, hence the VSC's superiority.
Maybe this will better explain the "building blocks" of VSC/ESP (and why TRACS is part of VSC) better than I can:
http://www.conti-online.com/en
/contiteves/themes/products
/electronic_brake_systems/abs_en.html
TC
Thanks in Advance
Michael
I was looking at a Highlander this weekend in Colorado and overall very impressed. Question I have is the salesman told me they were making 97% of the Highlanders as V6, AWD, Limited Package with Leather and most of the other options. I was wondering what you understand Toyota is building at the factory? A limited package V6/AWD is what I would like, but without the leather
Another possible cause would be the road surface itself. Did you test drive the HL on an unfamiliar road that may have had a "noisy" surface?
As far as less expensive car-based SUV's (which is presumably what you're looking for), there are lots of options including the Ford Escape/Mazda Tribute (sister cars), Toyota RAV4, Honda CR-V, Hyundai Santa Fe. Each of these cars can be had for under $25K. You might also consider the Nissan Xterra or Izusu Rodeo if interested in some offroad capability. Truck based SUVs tend to suffer from poor gas mileage and poorer safety features/ratings. Sounds like you may need to do some more research before hitting the showrooms. There are lots of good guides to SUVs on the newstands. Consumer Reports has one of the better ones. Good luck.
The other part of TRACS is the rev limiter. From a standing start, this is quite helpful on a 2 wheel drive vehicle. Combined with the braking action, this keeps you from spinning your wheels. On sand and snow on an AWD vehicle, this isn't really a desirable thing though. The rev limiter is an integral part of all other Toyota TRACS systems but was notably absent on the HL I drove.
Now, it is possible that Toyota deleted the rev limiter from the VSC/TRACS on the AWD models. That still doesn't answer the question of how TRACS can function in a vehicle with a center LSD. This is the central question I am asking.
Now, if I am correct that the AWD model with VSC does not have a traditional TRACS system associated with it, the whole thing makes much more sense. The center LSD transfers power front to rear as designed without interference from selective braking on slipping wheels. Power is not cut to the engine under heavy acceleration. The yaw control and position sensors selectively apply brakes and throttle to prevent lateral skids and all is well. Does this make sense? If not, how can the center differential keep power to the correct end of the vehicle when slipping wheels have brakes applied?
It'd be helpful I think if you could get access to a Toyota factory tech to get a definitive answer to whether the HL and RX share the same AWD/VSC/TRACS set up. From your observations, it sounds like there are some differences.
TC
-Front-wheel drive (FWD) with Traction Control (TRAC) or full-time four-wheel drive (4WD) with viscous coupling center differential
-Vehicle Skid Control (VSC)
This would seem to indicate that while VSC comes on both the front and 4 wheel drive, the 4WD does not have TRACS. It also says the center differential is a viscous coupling which is by definition a limited slip. This is making more sense now.
If it's anything along the lines of what happened with the Odyssey, it will come late but then be sold out months ahead of time while Toyotas will be selling well below MSRP.
- or the MDX vs the Lexus, for that matter....
Also, the purpose of privacy glass is just what it means, it makes it a little harder (though not impossible) for a passing pedestrian to see the contents of your vehicle. The glass is basically a "weak" one way mirror, seeing out should not be a problem, though slightly tinted. And I mean slightly.
"I am being stupid for wanting a FWD model with VSC? "
No! A skid condition can happen on any surface during a drastic emergency manuever. There have been plenty of links posted to other sites that have both graphic and video examples of why VSC and other similar systems work.
In the near future VSC will be as common as ABS is today. 10 years ago you could only find ABS on certain vehicles.
Dianne
dianne@earthlink.net
http://www.edmunds.com/chat/brauerchat022701.html
Drew
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