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Discussion Starter #1
Moderator note: this thread is a continuation of the astray 4WD portion of the discussion from this thread
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cardingtr said:
at above 18mph it will work if it detects difference in wheel spin(slipping) but still no AWD or VSC in the world can overcome gravity and inertial force in a slippery road especially if you are driving at more than 30mph. What is "auto-selective brake control" if no grip to repoint the car to its intended course
Grip has to do with the tires. That's why those are crucial and you don't cheap out on tires. Gravity pulls you downwards, you wouldn't want to overcome it anyway ;-).

Stability control systems don't beat the laws of physics, but what they do is work within them using a few techniques. You're incorrect regarding 30 mph. The systems work at any speeds and help to correct the vehicle to its intended path. Put it this way, you will be far better of with the system than without. Not all stability control systems are the same though. Some are better than others. The systems on MB and BMW vehicles (made by Bosch or Conti-Teves) are considered the most sophisticated on the market today, probably because MB invented stability control back in the early 1990's.

VTM-4 is quite simple really, in a manner of speaking. It uses the ABS wheel speed sensors to detect how fast the vehicle is going, and other sensors (ex. throttle position sensor) to detect if you're going from a standstill etc. From a dead stop, some power is routed to the rear (the rear differential clutch packs are energised to a certain extent) so that you minimise front wheelspin. Acura has said that the system will keep re-routing some power to the rear wheels if you are accelerating, at least up to a certain speed.

Once you reach this certain speed - Acura has never mentioned this threshold to my knowledge - the VTM-4 differential starts disengages completely leaving you with FWD only. The idea here is to save wear and tear on the clutch packs in the rear diffy (clutch packs do tend to wear out over time) and to also reduce some power transfer losses, as the vehicle is already in motion. Using these same ABS wheel speed sensors, the vehicle can compare the rotations of each individual wheel and if one starts to spin a preset limit faster than the other, this is interpreted as slippage and power is re-routed to either axle; this should work at all speeds.

What is interesting is that the MDX's AWD system does not have a centre differential. This means that it has to at least disengage one wheel for it to work in turns (or you will get binding), so you basically get 2WD or 3WD in turns on surfaces with a high friction co-efficien. On snowy/icy surfaces, there is probably enough slippage for the system to remain active, just as you can leave part-time 4WD systems engaged on slippery surfaces.

There are a few cons with this system, versus a permanent 4WD system with stability control. First of all, you don't get the benefit of permanent AWD since this is only a full-time part-time AWD system. This means that in turns, it is easier to overwhelm the tires' limits (causing slippage and understeer/oversteer) since the power is usually only directed to one pair of wheels.

With a permanent system, you are working far below the tires limits since the same amount of power is being routed to all four wheels, and not just two. This is why AWD vehicles can put down the power a lot quicker (hence accelerating far quicker and earlier) out of the apex than 2WD vehicles can.

VTM-4 does not know when you are sliding because it doesn't have any yaw and or steering angle sensors to tell it if the vehicle is not following the driver's intended path. Therefore it connect help at all. Not only this but even if it could help, because it is a torque-on-demand system, it requires that you are using the throttle (and hence getting the engine to produce enough torque) for it to be active. If you let go of the throttle, it goes back into its freewheeling (probably FWD) mode. There is also so much that reducing power can do. Stability control systems brake specific wheels to control directional stability and intent.

Another thing too...a spinning tire (when a tire spins, it means that it is overwhelmed) actually has <b>less</b> traction than a tire that is near the edge of its tractive limit. This is where traction control comes in. By braking the wheel and keeping it at its optimum limit, you get maximum traction, sort of similar to ABS. Spinning the wheels are useful when you are trying to build up your momentum. This is why most traction control and stability control systems have defeat/off switches.

As far as off-roading goes, traction control is also much more environmentally friendly as it doesn't allow for the same kind of soil erosion that a normal "spinning wheels" 4WD system does. Off-roaders don't like systems that can transfer power back and forth between axles because if you are in a delicate situation and inching your way past/through obstacles, the sudden unpredictable torque transfer to the opposite axle can be disastrous. Permanent or part-time lockable 4WD systems are ideal (as are long travel throttle pedals for much greater throttle control), since they have fixed torque split ratios.

The MDX's VTM-4 system is not unique. The Isuzu Trooper uses a similar system (and with a cool dash display) made by the same company, Borg-Warner. The major difference is that the Isuzu is primarily RWD whereas the MDX is primarily FWD. The Trooper's system can also be locked 50/50 like a traditional part-time 4WD system.

Whew...'nuff said. This has got to be one of the lengthiest post that I've seen on this board ;-)
 

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Drew said:
As far as off-roading goes, traction control is also much more environmentally friendly as it doesn't allow for the same kind of soil erosion that a normal "spinning wheels" 4WD system does. Off-roaders don't like systems that can transfer power back and forth between axles because if you are in a delicate situation and inching your way past/through obstacles, the sudden unpredictable torque transfer to the opposite axle can be disastrous.
Soil erosion? :rolleyes: Nice try troll, but the VTM-4 system is not a "normal 'spinning wheels' 4WD system". When you are in a "delicate situation and inching your way past/through obstacles" as you put it, there is no "sudden unpredictable torque transfer to the opposite axle" cuz VTM-4 has a Lock feature. I know this from personal experience, not from what I've read on the ML forum :p

Drew said:
Permanent or part-time lockable 4WD systems are ideal (as are long travel throttle pedals for much greater throttle control), since they have fixed torque split ratios.
Precisely, since the VTM-4 system is lockable, it is the ideal 4WD system to use your words. The MDX was also given a gradual throttle tip in per Acura's Canadian website. Problem with the permanent/full time systems like the M Class is since you can't turn it off, you are obviously gonna get worse mpg and have more wear and tear on the powertrain. Even on the highway with a V6, the M Class can't even get out of the teens in terms of mpg :p Meanwhile, my 'X blows the doors off the ML 320 while getting 23 mpg :) So you're partially right (not bad for a troll), a part-time lockable 4WD system is indeed ideal :)

Drew said:
Whew...'nuff said. This has got to be one of the lengthiest post that I've seen on this board ;-)
:p :D :eek: I think you spend more time on the MDX board then you do on the ML forum. Perhaps you have finally seen the light and are ready to trade in your ML for a 21st century SUV? :p



BTW, to answer Chuck's original Q, the only time the 18 mph limitation is mentioned is with respect to the "lock" mode, thus it would seem to me that the wheel slippage and acceleration modes of VTM-4 are available at higher speeds since no such limitation is mentioned. The information on the Canadian website would seem to back that up. I will post the Q over on the CR-V forum for CR-V engineer and maybe he will ask the MDX engineer for confirmation and a link to more definitive info.
 

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There you go again bringing up Mercedes-Benz products. I think you must have MB-envy. Drew said nothing about Mercedes in his very informative post. It really sounds like you should have bought a M-class because you either 1. want to prove you can go off-road, 2. you want to drag race. Neither of which the MDX does that well. A ML-55 or even a Brabus-ML (listed in guiness book of records as the fastest SUV) would suit your needs better. I do agree with your implication the MDX is a 21st century SUV as these type of 4x4 posers (MDX, RX300, Highlander, various Korean makes) did not show up until the turn of the century.

Mercedes Benz, unlike Honda, by the way, is very conservative in its numbers. Testing has proven the MB gets better gas mileage than the MDX. and it will easily out manuever the MDX on the highway. :D:D The MDX lacks stability control, there is no tiptronic control of the honda transmission, and has a tendancy to fishtail because of the heavy rear end. Off-roading does not mean driving down a dirt road. A locked VTM is no substitute for a lowrange, transfer case, and advanced traction control. In fact, driving on the highway at more than a few miles/hour with a locked differential is dangerous for most driving as the wheels need to turn at a different rates on curves. And don't forget, the VTM needs expensive and time consuming maintenance every 7500/15000 miles (if you put it under stress). The Mercedes transmission is sealed with no scheduled maintenance. The VTM is hardly a substitute for good 4WD. When you get stuck, I hope there is a M-Class or G-Class there to pull you out. :p

I hope Chuck got his answer before the name calling started again on this forum. :( You should try to have fun with your vehicle if you can and not get so upset when someone has a differing opinion. The MDX is a nice competant vehicle for the surburbs which is what Honda said it was designed for. (their comment that only 5% of the public takes it off-road)


GatorGreg said:


Soil erosion? Nice try troll, but the VTM-4 system is not a "normal 'spinning wheels' 4WD system". When you are in a "delicate situation and inching your way past/through obstacles" as you put it, there is no "sudden unpredictable torque transfer to the opposite axle" cuz VTM-4 has a Lock feature. I know this from personal experience, not from what I've read on the ML forum



Precisely, since the VTM-4 system is lockable, it is the ideal 4WD system to use your words. The MDX was also given a gradual throttle tip in per Acura's Canadian website. Problem with the permanent/full time systems like the M Class is since you can't turn it off, you are obviously gonna get worse mpg and have more wear and tear on the powertrain. Even on the highway with a V6, the M Class can't even get out of the teens in terms of mpg :p Meanwhile, my 'X blows the doors off the ML 320 while getting 23 mpg :) So you're partially right (not bad for a troll), a part-time lockable 4WD system is indeed ideal



:p :D :eek: I think you spend more time on the MDX board then you do on the ML forum. Perhaps you have finally seen the light and are ready to trade in your ML for a 21st century SUV?



BTW, to answer Chuck's original Q, the only time the 18 mph limitation is mentioned is with respect to the "lock" mode, thus it would seem to me that the wheel slippage and acceleration modes of VTM-4 are available at higher speeds since no such limitation is mentioned. The information on the Canadian website would seem to back that up. I will post the Q over on the CR-V forum for CR-V engineer and maybe he will ask the MDX engineer for confirmation and a link to more definitive info.
 

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zzdawg said:
There you go again bringing up Mercedes-Benz products. I think you must have MB-envy. Drew said nothing about Mercedes in his very informative post.
ZZDawg, you obviiously need to brush up on your reading comprehension skills :p And I quote:

Originally posted by Drew
The systems on MB and BMW vehicles (made by Bosch or Conti-Teves) are considered the most sophisticated on the market today, probably because MB invented stability control back in the early 1990's. [/B]
The irony of your remark is that in a thread where Chuck540Z3's question had absolutely nothing to do with MB or "soil erosion" :p , it was Drew who first brought up MB, and then proceeded to make several uninformed comments about the MDX's off-road capability. Yet here you are claiming that it is I who am obsessed with the M Class :p I'm just minding my own biz over here on the MDX forum, fending off one (take your pick of: jealous / misleading / misinformed / blind to reality) comment after another from the M Class trolls :p You don't see me posting over on the M Class forum do you? Surely if I was obsessed with the M Class I would be over there on their forum posting every day like the M Class trolls do over here :)
If anything, I'd say it's the MClass trolls who are obsessed with the MDX. Can't say I blame you though since the MDX has been winning all the awards of late when compared to the lard butt M Class (or anything else for that matter) :p


As my dear ol' grandpappy used to say: If you can't stand the heat, get out of the kitchen :) Or as I like to say: Quit whining :p
 

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zzdawg said:
There you go again bringing up Mercedes-Benz products. I think you must have MB-envy. Drew said nothing about Mercedes in his very informative post
Me thinks I hear the pot calling the kettle black here. Noone has any misperceptions on Drew's position - but at least Drew attempts to backup his claims with facts and figures (if not at least showing a little ML bias). Unfortunately, from some posters we see completely off-the-wall remarks like:
zzdawg said:
Testing has proven the MB gets better gas mileage than the MDX. and it will easily out manuever the MDX on the highway.
Would you mind posting a link or reference to ANY publication that has ever made that claim? (I will ignore the other references to the use and maintenance of the VTM-4 system since the only knowledge on the MDX you display seems to come solely from ML forums.

zzdawg said:
I hope Chuck got his answer before the name calling started again on this forum.
Funny, I didn't see any answer to Chuck540Z3's question in your response!
 

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Discussion Starter #7
<i>Soil erosion? :rolleyes: Nice try troll, but the VTM-4 system is not a "normal 'spinning wheels' 4WD system". When you are in a "delicate situation and inching your way past/through obstacles" as you put it, there is no "sudden unpredictable torque transfer to the opposite axle" cuz VTM-4 has a Lock feature. I know this from personal experience, not from what I've read on the ML forum :p</i>

Wow, name calling, juvenille and not at all unexpected from some people. Maybe if one looks pass the press releases (which are obviously designed to tout the vehicle's pros) then one can see things for what they are beyond that. Actually I have never mentioned what vehicle I drive either.

Wrong...because the torque needs to go somewhere when it's re-routed, it is perfectly possible for the wheel to break free. There is no brake application to stop the wheel from spinning free. As for the VTM-4 lock, yes of course it does help. However, it progressively reverts to FWD as you move above 9 mph, and you have no idea what the torque split ratio is after that. If you have ever seen the segment on MotorWeek with the Land Rover team discussing the Tread Lightly programme, you'd know that the soil erosion part is absolutely true, and this was demonstrated in their segment.


<i>Precisely, since the VTM-4 system is lockable, it is the ideal 4WD system to use your words.</i>

It is lockable only up to a certain speed. Some people like the system, and others prefer a more neutral setup. As a friend of mine says, "it's not god's SUV". ;-)

<i>Problem with the permanent/full time systems like the M Class is since you can't turn it off, you are obviously gonna get worse mpg and have more wear and tear on the powertrain.</i>

Worse MPG is not necessarily true. Consumer Reports has done fuel economy tests on Jeep Grand Cherokees with the vehicles in 2WD and permanent 4WD mode and there have been no fuel economy differences. Since the drivetrain (not powertrain) is designed for full time usage, there is not necessarily more wear and tear since this was taken into account in the first place.

<i>:p :D :eek: I think you spend more time on the MDX board then you do on the ML forum. Perhaps you have finally seen the light and are ready to trade in your ML for a 21st century SUV? :p</i>

Heh, when Honda shows to my satisfaction that they have as much committment to overall safety (not to say that the MDX is a poor performer by any means) then perhaps it will be in consideration. I'm not referring to just what you can see in the publically available tests, but what goes on behind the scenes.

It's not like I don't recommend the MDX to some people who insist on having a Japanese SUV. I like the neutral handling characteristics of a permanent 4WD/AWD system, so it is another reason why the MDX is not for me personally.
 

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Allow me to "slap some sense" into you (to use your words) The Worm was kind enough to point me to your lovely little post on the ML forum where you were quite literally trolling for trolls :p That is too funny :D

BTW, does any of this sound familiar? It should since you apparently wrote it :p

"with my '00 ML320 Elegance (early build 2000 model, first decade October 1999 production).

1) Window switch cluster replaced because of intermittent contact with the rear window switch (happened only
twice).

2) Transmission shift gate box replaced to cure the firm shifts when cold.

3) Door lock replaced because it was squeaking when cold.

4) Vinyl armrest/centre console lid replaced because of the vinyl bubbling due to the glue coming lose slowly
underneath.

5) Roof insulation re-glued to quell ticking noise from headliner.

6) Fuel pump/fuel sending unit replaced because of inacculate reading sometimes. ('00 MLs built after January
2000 have the updated pump).

7) Passenger side corner of dash repadded and felted to quell the vinyl creaking noise.

8) Washers added to keep glovebox lid tighter and from rattling."


It's now abundantly clear to me what's really going on here. Since you're stuck with one of the especially lame '00 M Class models, you're taking out your frustrations here on us by trying to deenigrate the MDX in the face of overwhelming evidence. Pretty sad actually.

The other thing I discovered in my little foray into the ML forum was some poor guy (it's on the first page) whose M Class has left him stranded something like 3 or 4 times already :p Personally, given the M Class' propensity for breaking down, I'd be afraid to drive one to the Taco Bell, much less a Nat'l Forest. It's a good thing MB offers road side assistance (I assume).

Get an MDX Drew, you know you really want one. Just think how much easier you'll be able to sleep at night knowing that your SUV is gonna get you to your destinnation under its own power, even if it's at the end of a "medium-duty off-road" :p
 

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Discussion Starter #9
Hmm, and the above post was on-topic for this thread?

And of course, you decided to leave out the last sentence in my message (no surprise), one that told it all.

<b><i>"And yes, I would do it all over again!"</i></b>

Weeping mirrors, front suspension thuds, wind noise, towing package issues, hmm, sound familiar? If I wanted to resort to that level, I could easily just quote things from the Problems section on this site. The common denominator is that regardless of the problems, most owners still enjoy their vehicles.

Oh and no reponse to the 4WD points in my previous message. Again, hardly surprising.

Of course, the whole point of this thread was to discuss VTM-4, but I guess some people just can't resist the chance to deviate off topic.
 

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Drew said:
"And yes, I would do it all over again!"/B]


I guess P.T. Barnum was right: there is a sucker born every minute :p

Drew said:
Oh and no reponse to the points in my previous message. Again, hardly surprising./B]


There is no point in responding to the so-called "points" of a pointy-headed troll :p (Aw, did I call you another bad name? I'm sorry :p ) For example, in your first post you were extremely concerned with "inching your way past/through obstacles". After I pointed out that the whole point of the VTM-4 Lock feature is to allow you to do precisely that, all of a sudden in your second post you became very concerned with what happens "as you move above 9 mph".

You backpedal faster than your lard butt M Class does 0-60 :p Thus it is pointless to argue your so-called 'points."

If you've ever actually gone off-roading, you would know that in areas with "obstacles" you wouldn't dare drive more than 18 mph in a $40K luxury SUV unlesss you are a complete fool. One would normally "inch" their way through it at less than 5 mph, but of course you already know that since you were the one who first brought up the concept of "inching" :p

I think it's time for the trolls to go back under the bridge from whence they came, unless they have more laughable misinformation, er, "points" to offer :p Perhaps they are just getting bored and restless reading the threads on their forum about all the mechanical breakdowns of the M Class? Or maybe they are just feeling lonely over there since the car mags have lost interest in them? Either way, I feel sorry for them, especially those driving the '00. :p
 

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RE: zzdawg's post

As an owner of both 2001 MDX base and a 2001 ML320, I would have to disagree with some of your statements.

Also, if you need ultra off-roading capability, both Benz and Acura will dissappoint compared to some others SUV's out there...

*Can't we all disagree in an agreeable manner?
 

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OT: Drew and Gatorgreg

I'm new to the group here. Also happen to be considering an ML and an MDX (as posted in Comparison forum).

I appreciate the depth of the technical discussion concerning the differences in performance between the two 4WD systems, and learn much from both of your perspectives.

More distracting are the personal snipes, name calling, and the incessant use of smilies.

I know this is a forum and is subject to personalities. I would think the forum benefits more when the dialogue continues than when it gets bogged down in personal comments and comes to a halt as a result.

As a reader, I rely on my own interpretation and judgement as to the motivation or veracity of particular comments, and if I don't understand something, I can always ask questions.

There are worse problems in the world than a disagreement on the particular merits of two elite luxury vehicles -- either of which the vast majority of the car-buying public would be proud to own if they could afford to.

Reading other sections of the forum, its apparent that the majority of the members don't squabble too often -- seems like the stakes aren't that high to warrant the baiting and the barbs that, unchecked, can undermine the valuable discussion.

Now we rejoin your regularly scheduled programming.
 

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Redirector,

Welcome to the forum--but more appropriately, welcome to the internet. There are no rules here--you make your own decisions, which is great--that means, if the remarks bother you, switch posts and stop reading this one. Like you said, most of the other posts on this board don't get to this level of warmth, so there's plenty other reading to do.

Threads like this are obviously inciting, so it's tough to not get a bit personal--wouldn't you agree, you lilly-livered newbie! ;)

Oops--I think I just annoyed you twice over!

Seriously, welcome, and enjoy the argument--we don't get many of them.

Rob :cool:
 

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Robyjo - Thanks for a little humor !!! It lightens an otherwise juvenile exchange. What's to come next - mine is bigger than yours?
 

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mine is BIGGER than yours- the mdx is larger than the ml320

what did u think i was talking about?:D
 
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