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Discussion Starter #1
I was reading the FA forums, and a poster named "Ed" posted a wonderful "laymans" description of the Murano's AWD system. What follows is a pasted post (credit to "AWDCVTVQ35DEMONSTER" from FA) - I am posting this here for the benefit of the members of this forum:

I finally got through reading at least the first post of every thread in the Murano forum here *is going blind*, and I noticed quite a deal of confusion regarding the type of drivetrain on our Murano, and I just want to make it precisely clear how it works, and mention on the side some alternative systems on the market.
The Murano (AWD models, of course) offers TWO modes of usage, but the ONLY difference between the two modes is at speeds ABOVE 30K/H. When the AWD Lock switch is DISabled, the car operates in THE SAME way, at ALL SPEEDS: the car operates as FWD (FrontWheelDrive) UNTIL slippage of either front wheel is detected, hencewhich, the rear wheels are provided torque! This happens at ANY speed, from 0.0001MPH, up the computer limited maximum of 116MPH, SO LONG as the AWD Lock is OFF.
WHEN AWD Lock is ENABLED, at speeds of 30KPH and under, the rear wheels receive an equal share of torque from the front wheels (that is to say, the two rear wheels combined receive a full 50% of the engine torque, and the front two wheels share the other 50%), which is excellent for unjamming the crossover from snow (up to a sensible limit; it's foolish to attempt taking on 3' of snow in a car with unlockable diffs). Once you exceed 30KPH, the AWD system returns to "normal operation," wherewhich is operates as stated in my previous paragraph, and the car sends the full 100% of the engine's torque to be split between the two front wheels, unless slippage is detected, and then up to 50% of the engine's torque is then distributed to the rear wheels to share. When the car has AWD Lock enabled, and is operating below 30KPH, and also in the rare case where sufficient slippage occurs with AWD Lock DISabled but a full 50% of the engine's torque is still sent to the rear pair of wheels, the car is then operating "as if" it has a "Locked Center Differential." The Murano does not have lockable front or rear differentials; what does this mean? Simply put, even WITH AWD Lock enabled at speeds below 30KPH, and ESPECIALLY with AWD Lock DISabled or at any speed over 30KPH, if one front wheel AND one rear wheel have ZERO traction, your Murano will be sending 100% (all) of its torque to the zero traction wheels, thus applying zero torque to the ground, thus affecting zero motion to the car; if you're stuck in so much snow that one front wheel AND one rear wheel have no traction whatsoever, you're stuck, pal. Of course, this also means that so long as you have ALL four wheels with grip, ANY three wheels with grip, or BOTH wheels at EITHER end at ANY time with grip, you Murano will be able to move; so don't go putting your Murano in a position where it has one front AND one rear wheel tractionless!
The Subaru AWD systems on all their cars have, basically, limited slip center AND rear differentials. In basic terms, this means that in order to get your Subaru totally stuck, you have to have NEITHER rear wheel, AS WELL as one front wheel tractionless. How you're going to get a Subaru hung up and tractionless at the whole rear end and one front wheel is beyond me, but knowing some people it's boudn to happen *shrugs*. If you have some grip at any two wheels at the same time on a Subaru, and the snow is not packed under the car too tight, the car will move, albeit with a certain deal of wheel slippage anyway, because these are not true locked diffs center and rear, but merely limited slip, but limited slip does guarantee at least minimal torque split.
If you REALLY want to go dominate a bunch of snow, you would want a car that allows FULLY LOCKED FRONT, CENTER and REAR diffs! I know a few cars that have this, including the Humvee (Hummer H1), a Land Rover Defender 90, and the Toyota Land Cruiser (models outside the USA as well as the previous generation and older ones here in the USA. The latest, USA V8 model, from what I hear, only offers lockable center and rear diffs). With all three diffs locked, you'd have to have the car hung up in such a way that NOT ONE WHEEL can put down enough torque to get it mobile. I hope this clears things up... a little...

Let me just mention two more things...
A Murano will also get stuck if both wheels on one side of it are gripless, as in BOTH right wheels, or BOTH left wheels, so be VERY careful driving it laterally off a high ridge of some sort (it's an ONroader! ) Again, this would not happen to a Subaru with its center and rear limited slips or to a fully front/center/rear locked super-SUV like the Humvee, Land Cruiser or Defender 90.
With regards to torque steer, the only time the Murano's AWD system will reduce (not eliminate, but reduce) torque steer is when you REALLY hit the gas hard, one front wheel spins (thereby inducing torque steer, as the remaining wheel that grips pushes the car to one side, tank-style!) and then the rear wheels torque up in response, again this situation would merely reduce, not eliminate torque steer.
One last thing regarding AWD systems out there. I noticed that more and more cars are using the, IMHO EXTREMELY STUPID, system of open diffs and braking at slipped wheels. The first example of a car employing such a system, as I recall, was the Mercedes Benz ML320. When a wheel slips, sensor catch it, and then the car APPLIES THE BRAKE at that wheel, in order to force, or redirect, torque through the driveline, back to the other wheels. If you ask me, forward progress does not subscribe to brake-torquing the sh1zz0 out of your driveline. I noticed that while the Lexus RX300 has a decent and sophisticated AWD system, for its son (or daughter, however you look at it), the RX330, will use a simplified multiple open diff system that applies brakes at slipped wheels, just like the Benz. It woes me to see such backwards progress.

And now for another session in WWD class...

I see that the Infiniti FX35 is often compared with our beloved Muranos. While it's an obvious and fair comparison, I'd just like to mention the difference in AWD systems between the two cars.

I've already mentioned the system used in the Murano, but just to reiterate, it's a normally FWD car, and even the center diff to the rear "axle" is constantly in motion! The rear wheels are activated by application of torque at the rear of the wheels, where a torque converter applies torque to the open rear diff from the spinning center drive axle, upon slippage. Any AWD cars based on the FF-L platform (the underlying "chassis" of the current Altima, the new Maxima, the Murano and the upcoming Quest, meaning Front-Engine, Front-Wheel-Drive, Long) will use a similar, if not identical AWD system to the Murano, give or take a couple limited slip diffs, instead of fully open ones like Murano.

The FX35/45, which is based on the FM platform [Front Midship, from the JDM (Japanese Domestic Market) G35 (aka Skyline, non-GT-R, also our Infiniti G35), also the underpinning for our 350Z, our G35 Coupe, our G35 Sedan, the FX35 and the FX45], uses a virtual "backwards" version of our system. What happens is the car normally drives in RWD, like the Z. On the FX35/45, the car also is constantly driving a center axle like the Murano does, and if wheel slippage occurs, torque convertors in the front will apply torque from the spinning center drive axle to the front wheels. This, as I said, is virtually an exact reverse version of the Murano's system.

Neither system is superior, because, from what I can tell, neither car has limited slip diffs anywhere. Basically speaking, the only difference is that the FX will show oversteer characteristics when driven hard until the front wheels kick in, and the Murano will normally show understeer (being RWD vs. FWD in nature). Preference is based on your style and skill of driving, but the chassis of the FX does hold the inherent advantage of its front-midship mounted engine, whereat the engine is BEHIND the front axle! This endows thw FX with a remarkable front/rear weight distribution of 54/46% Murano is closer to 61/39, which also further contributes to characteristic understeer when driven harder.

If you ask me, the superior weight distribution is offset by the lack of CVT on the FX, which also, in VQ35DE form, weighs 200lb. more than the Murano. The VK45DE version (FX45) has a massive power advantage, but costs five-figures more than our "humble" Murano.
 

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Discussion Starter #2
I will note that what was not stated in the post above is that the Infiniti's ATTESA E-TS™ AWD system (Advanced Total Traction Engineering System for All Electronic Torque Split) defaults in AWD during every start of accleration from standstill, and then switches to RWD if slippage is not detected. In other words, on a dry sunny day, the system starts off in AWD momentarily, then switches to RWD in normal driving each time you start and go.
 

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well.. maybe someone should get the individual to explain this..
(I agree with his assement that the MO ACTS like it has an open differential, but NISSAN claims differently)

From the Manual:

"The VDC uses a brake Limited Slip Differential
(LSD) system to improve vehicle traction. The
brake LSD system works when one of the driving
wheels in spinning on a slippery surface. The
brake LSD system brakes the spinning wheel
which distributed the driving power to the other
drive wheel. If the vehicle is operated with the
vehicle dynamic control system turned off, all
VDC and traction control functions will be turned
off. The brake LSD and ABS system will still
operate with the VDC system off. If the brake
LSD system or the ABS system is activated, the
slip indicator light will blink and you may hear a
clunk noise and/or feel a pulsation in the brake
pedal. This is also normal and indicates the
brake fluid pressure is controlled properly.
While the VDC system is operating, you may feel
a pulsation in the brake pedal and hear a noise or
vibration from under the hood. This is normal and
indicates that the VDC system is working properly.
The computer has a built in diagnostic feature
that tests the system each time you start the
engine and move the vehicle forward or in
reverse at a slow speed. When the self-test
occurs, you may hear a clunk noise and/or feel a
pulsation in the brake pedal. This is normal and is
not an indication of a malfunction.
VEHICLE DYNAMIC CONTROL
(VDC) SYSTEM (if so equipped)
"
 

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SHIFT_FASTER
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A Brake LSD is not a true LSD. It applies brakes to one wheel (the slipping one), and because of the way an open differential works, the power is sent to the other wheel. Minus the power transferred into heat energy in the brakes.

Good for helping restore control if it is lost (because it also slows you down), but almost useless in any other scenario.
 

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Thanks for this detailed explaination. Call me silly but I for "normal" driving, like the MO is designed for, what is the advantage of the AWD? If both sides slipping or one front and one cross rear (or reverse) they you got nothing. Does the AWD really provide any benefit over the FWD?

Don't get me wrong I've fot an AWD but as I questioned it when I purchased it and question it again. I think I could have saved a couple of $$$ and ended up with the FWD and never have regretted it. No?
 

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Discussion Starter #6
Gonzo said:
Thanks for this detailed explaination. Call me silly but I for "normal" driving, like the MO is designed for, what is the advantage of the AWD? If both sides slipping or one front and one cross rear (or reverse) they you got nothing. Does the AWD really provide any benefit over the FWD?

Don't get me wrong I've fot an AWD but as I questioned it when I purchased it and question it again. I think I could have saved a couple of $$$ and ended up with the FWD and never have regretted it. No?
In everyday normal driving, such as on slick roads, it is unlikely a wheel will lose traction entirely. Therefore, the AWD system will generally function as advertised - i.e. give you traction to all four wheels when you need it. FWD is fine for most situations, but having driven in snow, I would take the security of AWD anyday!
 

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Definitely AWD here in Central MA. There are a lot of hills, and I've lost track of the number of snow storms we've had where people were slipping, sliding and stuck on hill with their FWD vehicles. I would wait until it was clear and just sail on by them in my AWD. If you live down south or someplace that doesn't see much snow or isn't muddy, I wouldn't spend the extra $$$ as the FWD will be perfectly fine for you.
 

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Tyler_Canada said:
Good for helping restore control if it is lost (because it also slows you down), but almost useless in any other scenario.
It prevents "smokey burnouts" for a faster take-off. :4:

If using the gas a bit on a slippery corner, it works effectively to reduce understeer.

It helps quite a bit in any slippery weather, including wet roads, if you accelerate quickly. If you normally accelerate quite slowly, there probably isn't much for it to do.
 

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awd resale value better than fwd ?
 

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AWD resale value is MUCH better than FWD.

As a rough example, when I bought the MO I sold my 1990 Ford Bronco II with 170,000 miles on it, body was in good shape, engine was still rockin' for $1000 without haggling. If it was FWD I would've been lucky to get $300 up here.
 

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Nissan Canada's lease program indicates residual after 48 mths- SL AWD 49.7% SL FWD 47.7%....I think market value 4 years down the road will be higher than 2% for AWD's.
 

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Yeah, the difference is definitely more noticeable long term. I intend to have my Murano for many many years, so it is definitely a big selling point for me.
 

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Limited Slip Diff

Anyone know if a limited slip diff from a Maxima or some other Nissan could be installed on (i.e. interchangeable with) the Murano?
 

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Eric L.,

Thank you for the excellent description of the AWD system.

But what about the contradiction between your description and darrylburke's quote from the MO manual? Is the manual wrong?

Respectfully,
Dave G
 

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Discussion Starter #15
From what I understand, the AWD Murano with VDC do indeed have a brake-limited slip front differential. I cannot take credit for the detailed writeup, as the original post was from the FA boards.
 

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Redbeard said:
Eric L.,

Thank you for the excellent description of the AWD system.

But what about the contradiction between your description and darrylburke's quote from the MO manual? Is the manual wrong?

Respectfully,
Dave G
Read the 4th post in the thread, by me.

There is brake limited slip front and back, but they are not Limited Slip Differentials. They are open differentials. Noone should call it a "Brake Limited Slip Differential", because the brakes are not part of the differential.

Do a web search for "brake limited slip", and maybe you can find a more detailed explanation.
 

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Ok, I did the legwork.

Here is an article that explains well all the different types of differentials, including BLSDs. Note they call the BLSD an EDL. It is what is on our vehicles, and not what Nissan calls TCS or VDC.

http://www.houseofthud.com/differentials.htm
 

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OK, I admit it, I am totaly confused.

My take on this thread is that the initial post by Eric L (originally written by Ed) refers to an MO that is not equiped with VDC. If such a vehicle has both left wheels spinning on a patch of ice, the vehicle will not move.

On the other hand, if the vehicle has VDC, the brakes will kick in on the wheels that are spinning, and torque will transfer to the other wheels.

But wait! The LSD still stays in effect when VDC is turned off!! So the vehicle will still transfer torque to the other wheels when VDC is turned off!?

I give up. This is too much for my feeble mind to comprehend.

Dave
 

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Yes that makes perfect sense. The off switch is not a power off, it's a request to the computer to not engage the software that allows VDC to do it's thing. VDC adds the yaw sensor, but the rest of what it takes I suspect is already in every Murano made.

Throttle control? Already needed for the CVT. Brake control? Already needed for ABS.

The same goes for traction control.
 
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