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Discussion Starter #1
It has been snowing here in east coast, and lots of slit/black ice on the road. My murano does not have VDC, it is a standard awd SL model.

Questions:
- will the awd kick in if necessary or should i be better off turn on the awd when the road seems icy?

- will having the awd but w/o vdc helps in snow condition?

I still think vdc *and* awd are redundant.
If your car is 2-wheel-drive then having vdc/stability control is a big help on slippery roads or when your car is loosing the grip. But having AWD, the car will redistribute the power and adjust the rotation of the other tires acordingly. So why VDC and AWD?

Any one kind enough to explain? -- Thanks ....
Drive safely in (and 'on') the snow ~
:D
 

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Turning the AWD "on" only works under 18mph.

AWD is on all the time and will engage when necessary. AWD lock is for very slippery and slow conditions.

Yes, AWD will provide greater traction in slippery conditions then FWD.

No, AWD is not a replacement for VDC. VDC is not a replacement for AWD. The two are very different systems and have very different effects. And they compliment each other well.

AWD provides power to front and rear axles.

VDC provides independent braking of each wheel.

AWD is for improved movement in slippery conditions. In other words more traction/velocity/acceleration.

VDC is for increased handling stability when either the front end or rear end or both slips left or right. In other words tries to stop the car from spinning out of control when you exceed the traction limits.

The two systems do share one thing in common. They will not make the vehicle stop quicker in slippery conditions.

As a side note, although AWD is better than FWD in slippery conditions, FWD is better than RWD in slippery conditions. For both FWD and AWD, applying power gently through a slippery turn will help pull the front end through dragging the rear. On a RWD vehicle, applying power kicks the rear end out and the front end tends to drag and the result is a spin. Under same conditions, applying power on a FWD or AWD or 4WD will pull you through the turn (best rate of turn possible) without the rear end kicking out.

What I did once upon a time was practice in a BIG empty freshly covered icy/snowy parking lot that you know has no concrete dividers/curbs, lamp posts, holes, or anything else that you might bang into and damage your car. Make sure there are no dry patches, lot must be flat and slippery everywhere.
 

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Here is an example of VDC. If your rear end starts to swing out due to slippery conditions, the VDC will apply braking to the proper wheels to prevent it. Non equipped vehicles will continue into a slide out if the driver is not capable of controling the skid. I have this feature on my Acura TL and believe me, it is awesome.
 

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Also, the differentials in the MO are "open".

An AWD or 4WD that has "open" differentials means that it is really 2WD, 1WD on the front axle and 1WD on the rear axle. A FWD only or RWD only vehicle with "open" differentials really has only 1WD.

On these vehicles, you can gently press on the brakes and it will act like a limited slip differential splitting power across the axle to both wheels. But it's hard on brakes, only used when you get stuck.

A "true" 4WD will have limited slip or detroit locker differentials. I built a Ford F150 for offroading and put a detroit locker on the front axle and a limited slip on the rear axle with manual front hub locks. I still got stuck, left the truck in gear, got out and walked around the truck watching all four wheels spinning. That's why they make winches.
 

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Discussion Starter #5
Enforcer, thanks for the reply... snowride more~

Ok consider your situation:
Here is an example of VDC. If your rear end starts to swing out due to slippery conditions, the VDC will apply braking to the proper wheels to prevent it. Non equipped vehicles will continue into a slide out if the driver is not capable of controling the skid
From the www.howstuffworks.com for AWD versus VDC, here is my conclusion:

If my rear end starts to swing out due to the slippery snow
VDC will slow down the slipping tire(s) that loose traction . The AWD, at a fraction of time later, will kick in and compensate the lost of torque to the other 3 tires by giving more torque to them. Hence, the vehicle pass through the snow/slit puddle without significantly relizing that it has slipped/lost traction on one tire. Without the vdc, the awd will compensate, but the sensation of loosing grip (slip) will be more pronounce. If you loose the traction too much (let say slip happen at higher speed), the AWD may not be able to compensate at all. Am i correct? :eek:

Now, i start to regret not getting the VDC-StabilityControl package!
 

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What you can do for an official

explanation is go to the source.

Continental Teves supplies the "VDC" to Nissan.

At their level it is known as the ESP and is used in many diferent makes and models.

You can find some info here at their Homepage complete with a "demo" of what it does and how.

http://tinyurl.com/y2o0

WHAT? You didn't think Nissan built this did you?

Homer
 

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SugarRushMurano

The AWD will engage by sensing wheel slip during acceleration which engages the rear wheels to compensate. (as in loss of traction because to much throttle was applied for the conditions encountered and NOT a sideways skid) If the wheel slip is still present, the traction control will take over by applying brakes and/or reduce engine output to the wheels to compensate.

In a nutshell, the AWD and traction control will prevent you from spinning any tires due to stomping on the gas pedal.

The VDC works for lateral slips such as the rear end slipping out. A good example of this is taking a corner too fast in slippery conditions and the rear tries to let loose. This example of a skid was caused by the side forces being too great and loosing traction, not stomping on the gas and I believe this is where you are confused. The sensors detect this movement and apply the brakes to the necessary wheel(s) to prevent it from happening. AWD cannot compensate for this and the rear end will simply swing out until driver skill compensates.
 

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I've had one occasion to "test" the VDC. I had about 1500 miles on the M-o and a deer ran out in front of me on a rainy night. I spun the steering wheel and panic slammed on the brakes and went into a sideways skid. In a split second I was past the deer and going straight down the road. The only thing I could say was, "How the hell did that happen?" It was pretty amazing. I didn't do a thing, but the car straightened out by itself. It made me remember a discussion I was having with my dealer when I was trying to decide if I wanted the VDC or not. His comment was "it will be well worth the $700 extra if it saves one accident." Makes sense now!
 

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Discussion Starter #11
pbeinetti .... i am without VDC...

should i worried :( ....
I wish there is an aftermarket one to add...:(
 

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Re: pbeinetti .... i am without VDC...

SugarRushMurano said:
should i worried :( ....
I wish there is an aftermarket one to add...:(
Why would you worry?

Look, I lived in DC and northern Japan (I'm in Texas now). I've been through blizzards with nothing but a RWD Mazda pickup truck. I just threw some sandbags in the rear and drove carefully. I've never been in an accident.

Look along the median of the Beltway or 95. I bet it is littered with abandoned SUVs, many of which have 4W or AWD and some with some sort of VDC like system. They are stranded because they did something stupid. VDC is a good system but NOTHING is better than common sense and good driving skills.

Just be carefull on the roads and think.
 

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Discussion Starter #14
sgt beavis and snowride.. thanks

I am without VDC.
But i am happy, because i am drivig an AWD.
Afterall, nothing beat common sense.

Thanks everyone :D
 

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I'm glad someone brought up 'driving with common sense."

My dad had a theory of 4WD back in his Jeep'ing days. 4WD only gets you stuck that much further off the trail.

Rant On/

With all the crap we have put in cars to help people drive i.e. ABS, VDC, AWD, Traction Control - people still have to remember to think when they are driving. Slow down when the weather is bad - I don't care if you're driving a Hummer - there is going to be a reason for a panic move - plan ahead for it.

FWD vs RWD - personally I call BS. I'd MUCH rather drive RWD in bad weather. Doesn't it seem odd the for years after the mainstream has had this FWD rulez attitude - Police cars, highway troopers are still driving RWD. There are times when it is better to hit the gas to avoid an accident - what happens if you punch the gas with the wheels TURNED in a front wheel drive car - you go STRAIGHT! Braking from FWD to RWD isn't any different.

/Rant Off
 

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SugarRushMurano,

I think what you said is true, but I don't look at it that way. AWD or 4X4 to me is not a safety device in slippery conditions, VDC is. Now you can use AWD to pull you through a turn faster (shorter turn radius), but AWD in of itself just helps you get more traction. For example going up a slippery hill. What putting power to both axles does is increases your drive contact patch surface area (drive wheel friction).

Again, neither of these two help you stop any faster. ABS/EBD does but we're not talking about that right now.

Likewise, I have driven 2WDs and 4WDs for years in various places I have traveled to and lived in and have never had an accident. A 4WD memory comes to mind. I was driving down the interstate in moderate snow (6-8") with my Cherokee in the left lane where a lot of cars and SUVs were running in the right lane. The right lane had deep ruts and the left lane was virgin snow covered. As I looked in my rear view mirror I saw 2WD cars and 4WD SUVs try to pull into the left lane (where I had just cut a path in) and they ended up spinning out in the median. A 2WD memory comes to mind, when I lived in Ohio I was driving a 1965 Pontiac Catalina with snow tires and concrete blocks in the trunk. The roads were iced over and everything was closed but I had to get to my grandmas because she had a water leak. Nobody was on the road, not even the salt trucks. My secret, I put the right two tires in the berm and gently applied brakes to get traction and went slow.

My point is, there is a lot to know about both 2WD and 4WD and how to use them in various conditions. What we think is "common sense" often isn't and sometimes is anti-intuitive. I have some offroading and 4WD experience so I know some things, but not everything. There is always more to learn. The best thing to do is find an empty parking lot and teach yourself as previously mentioned. There is also a lot to learn about the capabilities and limits of any given vehicle. While there are some similarities between my MO and Jeep, there a lot of differences.

Also, you don't need AWD or VDC or even ABS or EBD. But each one of these marvels of engineering adds a different capability and complement each other well. But none of them will overcome lack of experience or ignorance. Ignorance is defined as absence of knowledge. We are all ignorant until we learn.

A few things that come to mind:

In all cases, go slow and plan ahead, your stopping distance on slippery conditions is much much greater. Give yourself room. Also, when moving, energy is defined by onehalf times mass times velocity squared. In other words, it takes an increased proportionate/linear amount of more energy to accelerate or stop the heavier the vehicle is, but increasing speed increases energy by the square. Say mass is 1 and velocity is 1, energy is .5. Say mass is 10 and velocity is 1, energy is 5. Say mass is 1 and velocity is 10, energy is 50! Velocity is drastically more important than mass.

Traction is basically friction. Anything you can do to increase the friction between your tires and the road is good.

Stay out of ruts, always try to cut your own path. I love a freshly snow covered road that no one has been on. If ruts are present, ride in the fresh snow lane or if one lane, ride on top of the hills not down in the valleys. Even if the rut is only a half inch deep. Cut your own path, don't follow in someone elses. If you can't get both sides on top at least get one side on top. Remember you only have so much clearance under your vehicle, you don't want to hang up the chassis (high center) or drag it.

Let some air out of your tires to flatten out the tread blocks, this increases the surface area contact patch and increases tread flex to kick out snow that builds up in the treads. But put air back in once the roads clear or they become discontinuous (wet/dry).

If in an emergency, put the right side of your vehicle on the berm, but know the road well so you know there are no concrete curbs, steep drop offs etc and realize that you could end up with a flat.

If there is a small particularly slippery spot (hard packed snow or ice) or you are stuck (make sure your chassis isn't hung up, dig it out if it is), put sand, dirt tree branches or something in front of the tires and over the slippery spot.

Don't spin your tires. I don't know how many times I see somebody gunning their engines with their tires rotating a hundred miles an hour and the car is just sitting there or creeping. Apply slight power and gently tap your brakes to act as a temporary limited slip differential. This will engage the other drive wheel(s) on the axle(s) and double your friction. Again, friction is the key. Static friction (before slip) is greater than dynamic friction (after slip). If that doesn't work, try some of the other previously mentioned ideas. If none of these work, you need better tires, chains, studs or a plow.

Discontinuous drive path - dry spots. Try to avoid these, either stay on all dry or all snow. Sometimes you can't, sometimes there is a dry spot or slippery spot all the way across the road. What will happen is the wheels will grab and slip. Try to go through these such that the wheels are perpendicular to the discontinuity. Try not to take them at an angle or in a turn.

Discontinuous drive path - ruts. Be careful not to high center when crossing over the high spots of ruts. Avoid hanging or dragging the chassis. Try to cross these at a very slight angle, first ease your one sides front wheel up on the high spot of the rut (mountain) then ease that sides rear wheel up. If the distance from the mountain to the valley exceeds your chassis clearance, don't go over the other side such that you straddle the mountain. You want to straddle the valley. If you have to cross ruts, drive a little further and plan ahead where you won't run the risk of high centering or dragging the chassis, where the rut isn't so deep. If the rut is across the road and you have no choice, make sure you have chassis clearance and creep over it, if you don't have clearance (mountain is too high), get out the shovel and level the rut. The key is, watch your chassis clearance.

Chunks of packed snow or ice (snow boulders). Try not to drive over these (under chassis). It is better to hit them on the inside edge with your tire then to hit them with something under your chassis. When you hit them with your tire, either it will break apart and or get pushed out of the way. But make sure you hit it one the inside edge such that if it pushes, it doesn't push under the chassis but out away to the median or ditch.
 

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Discussion Starter #18
enforcer..you are great. Thanks for the tips

.. Now i learn new things.
Thanks for posting something that long.

Common sense i was referring to is to reduce speed when it is snowy/black iced/ slippery. You know, be the defensive driver rather than the aggressive one.
 

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Oh yeah, defensive driving works. Watch all the other cars on the road and watch the road. Drive slow enough that you have time to plan ahead and avoid an accident. That means your reaction time and the reaction time of your vehicle under those conditions, when in doubt give yourself lots of margin. You also have to judge the other cars and drivers and figure out what they are doing. Don't ride in somebodies blind spot, either drop back or pass. Check your rearview mirrors frequently, don't just plan-ahead ahead of you, plan-ahead behind you.

Now if only my Escort had an optional cell phone jammer attachment...
 

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Discussion Starter #20
it's funny you talk about cellphone and driving...(m)

My audi was rear ended by this lady on a parking garage downslope about a year ago. It was low speed, definetely less than 10 mile per hr. When her eclipse hit my rear, i said what the h*ck, this is a parking garage. So i went out, and see her still holding her cellphone to her ear. Turns out she is on the phone and did not notice that there is another car (me) in front on the downslope. Wtnesses were all over, there are 2 ppl just getting out of the car, laughing, for example.

Bumper need repaint, $550. She paid. All because of cellphone.
We need cellphone jammer mod indeed :p
 
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