4wd Vs Awd??

[lesnar]

What's the difference? Do you turn it ON/OFF with a switch in the car? or is it automatic? And is there a major fuel efficiency between the two and compared to a traditional 2WD?

[Tijuana]

I believe 4WD only turns on when needed. Like on slippery turns or whatever. AWD is when all the wheels turn at the same time, all the time. I think most 4WD are actually RWD?

[nano]

i depends on the auto i have an Escape its is front wheel drive but 4X4 when the wheels slip i have other family members that have larger suv's and they have a leaver or a buttor or some have a dial

[Anessa]

Depends on the maker to show their preference for RWD or FF in the AWD system. BMW likes their xDrive to have the rear wheels bias because of the rear wheel nature of the non AWD BMWs. Volvo's have a preference for front wheels then the coupling adjusts when wheels slip.

[Evil Techie]

Depends on the maker to show their preference for RWD or FF in the AWD system. BMW likes their xDrive to have the rear wheels bias because of the rear wheel nature of the non AWD BMWs. Volvo's have a preference for front wheels then the coupling adjusts when wheels slip.

do u know what ratio subarus are?

btw i think AWD and 4WD are rated differently by insurance companies

here is a good and simple explaination for AWD vs 4WD that i dug up from google in 2 seconds
http://www.delalbright.com/Products/products_awd.htm

ALL WHEEL DRIVE:
Definition: A vehicle where all four wheels are driven, but there's no transfer case like a four-wheel drive rig. Most AWD setups are full time systems for year-round driving, and use a viscous fluid coupling center differential instead of a transfer case to route drive torque to all four wheels. This allows the front and rear wheels to turn at slightly different speeds when turning on dry pavement. Most folks do not consider this the same as four-wheel drive. It can be useful (and more fuel economical) in pavement driving where you're mainly negotiating bad weather conditions.

FOUR WHEEL DRIVE
Definition: A method of driving a vehicle by applying engine torque to all four wheels thru the use of a transfer case, differentials and hubs. Various schemes are used for 4WD including part-time, full-time and variable four-wheel drive. To help cut the drive train drag (and reduced fuel economy) that most 4WD's have, a transfer case is included that allows the driver to select either two- or four-wheel drive depending on driving conditions. Some performance cars have full-time variable four-wheel drive and use a computer-controlled transfer case to route power between the wheels.

It's important to note that even in 4WD, you still have only two driving wheels; one front; one rear. A normal passenger car is essentially one wheel drive, because the other one can slip. So a 4WD rig, with the front axle engaged, now has two wheels driving. Then if you add a locker to the rear, you've added one more wheel, to make your rig three-wheel drive. Add a locker to the front, so no tires can spin, and you have TRUE, 4-wheel drive, all four wheels driving.

[mudmojo]

do u know what ratio subarus are?




Most (maybe even all?) Subaru MT's are have a 50:50 front/rear torque split regardless of load. The lines get blurred when you start talking about factory specials, heavy machinery and different markets.

STi torque splits are driver adjustable since about 1996.

STi torque splits can be automatically left for the DCCD ECU to determine (from 2001 onwards) based upon yaw rates(at least from 2005 onwards)/tire slippage rates/tp.

The AT's torque splits are 90 front/10 rear (at least for recent NADM models) . Don't know if that's under load or not though.

[Evil Techie]

btw Subaru AWD's suffer from lacking low torque since its not 4WD?

[mudmojo]

Torque as in at the engine or on the ground? I'm thinking you're talking about to the ground because engine wise, it's the only Japanese manufacturer that makes or made torquey 4 cylinder engines down low in the rev range. Nissan and Toyota make honourable mention engines torque-wise but they are 6 cylinder engines.


Are you talking the Subarus not having a High-Low transfer case like most trucks are equipped with?

The Subarus consumers can purchase in North America are not trucks and as such, do not come with H-L cases. I'm assuming that they don't stand to gain any money by putting a truck transmission into a car but that's just speculation on my part.

For example, the Forester is based off an Impreza chassis.

[achc]

If you car is AWD, it CANNOT BE TURN OFF. Its full time AWD. That means the computer checks the wheels like 200 times a second (depending on what car you have) to see if it slips or loose traction, etc. It then transfer power to wheels to keep the car going at where the driver wants it to. Most SUV now a days are AWD. Most sports car that runs on more then 2 wheels are AWD not 4WD.

4WD is you can manually adjust which wheels to drive the car. This is used for real offroad. You can set front wheels only, rear wheel only, or 4 wheels. In basic 4WD, it is usually rear wheel only or 4 wheels. But an expensive top line offroad vehicle that is 4WD lets you drive with front wheel power only as well.

There is an ON/OFF switch for 4WD but none for AWD.

AWD makes driving easy but extream offraod or hill climb, you need 4WD

[P90Puma]

AWD makes driving easy but extream offraod or hill climb, you need 4WD

I agree with almost everything you said other then this. You are generalizing AWD/4wd with respect to what cars they are usually on.

This has nothing to do with the actual AWD/4WD system.

[mau108]

to my knowledge its either 4x4 or AWD. 4WD I think is toyota's version of AWD ?

4x4 is all time 4 wheel drive meaning all 4 wheels are getting the same power (well with technologies these days they can adjust the power to each wheel so ...)

AWD is pretty much FWD or RWD car but when the system detects slippage it kicks in the opposite wheels (FWD its the Rears, RWD its the fronts) Subaru has one of the best AWD systems as with Audi's Quattro.

Note Traction Control is not the same as AWD, traction control will detect slippage and adjust the powers to those wheels rather then activate another system in the case of AWD.

[mudmojo]

to my knowledge its either 4x4 or AWD. 4WD I think is toyota's version of AWD ?

4x4 is all time 4 wheel drive meaning all 4 wheels are getting the same power (well with technologies these days they can adjust the power to each wheel so ...)

AWD is pretty much FWD or RWD car but when the system detects slippage it kicks in the opposite wheels (FWD its the Rears, RWD its the fronts)



Stop the insanity! Where are you getting this information from?

[seftonm]

to my knowledge its either 4x4 or AWD. 4WD I think is toyota's version of AWD ?

4x4 is all time 4 wheel drive meaning all 4 wheels are getting the same power (well with technologies these days they can adjust the power to each wheel so ...)

AWD is pretty much FWD or RWD car but when the system detects slippage it kicks in the opposite wheels (FWD its the Rears, RWD its the fronts) Subaru has one of the best AWD systems as with Audi's Quattro.

Note Traction Control is not the same as AWD, traction control will detect slippage and adjust the powers to those wheels rather then activate another system in the case of AWD.

4x4 is a form of 4wd but it is not full time. For the majority of trucks, 4x4 means a part time system engaged and disengaged by the driver.

[Narci]

AWD is what it says...ALL WHEEL DRIVE. Whether it's 50/50 30/70. As long as all 4 wheels ALWAYS drive..it's AWD.

Here's the tricky part.

4WD means the driver and engage and disengage which wheels are driving. Olden days, you needed to lock the hub and drive for a bit to engage and disengage the 4WD. Then there was a system that looked like an automatic shiftbox in the car that alowed drivers to engage and disengage front wheel, rear wheel, 4 wheel, high and low. Now it seems like it's push button.

Toyota and Honda (RAV4 and CR-V) are not driver controlled 4wd systems. Honda calls thiers Real-Time which mean it's front wheel drive until it detects a slip then it engages 4 wheel drive on it's own.

[warpdrive]

Most (maybe even all?) Subaru MT's are have a 50:50 front/rear torque split regardless of load. The lines get blurred when you start talking about factory specials, heavy machinery and different markets.

STi torque splits are driver adjustable since about 1996.

STi torque splits can be automatically left for the DCCD ECU to determine (from 2001 onwards) based upon yaw rates(at least from 2005 onwards)/tire slippage rates/tp.

The AT's torque splits are 90 front/10 rear (at least for recent NADM models) . Don't know if that's under load or not though.

Some of their automatics, such as the one is the WRX or higher end performance models have a 45/55 FR split (they call it VTD automatic)

[cipher]

AWD, 4WD whatever is just a name that the manufacturers use and has nothing with the actual system on the vehicle. It used to be that AWD was for passenger cars and 4WD meant a truck with a transfer case. But these days it's all blurred with many trucks & SUVs getting similar systems as passenger cars.

[M-e-X-x]

for those that have ACTUALLY driven these 4WD and AWD, you have the right to comment... for all others, please refrain from replying...

with that said, i have driven 4WD and currently own an AWD car...

4WD can have a transfer case for manually controlling the torque split, but then there are the permanent 4WD systems (aka Jeep brand)... they are 4WD all the time, no matter slip or not... my family has a pathfinder with a shift-on-the-fly system (transfer case) that does a 50/50 split when the driver sets it... 4WD can do low range and high range, as is the nature of most transfer cases i've encountered... and yes, a lot of 4WD shift-on-the-fly systems are RWD when not engaged...

AWD is permanent split between front and rear, may it be 50/50, 40/60, etc. for subaru's 4EAT (aka automatic transmission), 1st and R are 50/50, 2nd i'm not sure is 50/50 or not, but as u go higher in gear, it's 90/10.. the 4EAT in a wrx is 45/55 as one other poster mentioned...

as well, those 'torque transfer when slippage is detected' ARE NOT true 4WD/AWD systems...

[achc]

I agree with almost everything you said other then this. You are generalizing AWD/4wd with respect to what cars they are usually on.
This has nothing to do with the actual AWD/4WD system.

AWD makes driving easy but extream offraod or hill climb, you need 4WD

I don't get your point. Yes I mention what cars have 4WD and what cars have AWD, but I did mention how AWD works (a computer sensor) vs 4WD works (drivers select which wheels to drive the car)

I even answered lesnar question directly about if this system can be turned off manually or automatic.


What's the difference?
Do you turn it ON/OFF with a switch in the car? or is it automatic?
And is there a major fuel efficiency between the two and compared to a traditional 2WD?

I wrote before:

If you car is AWD, it CANNOT BE TURN OFF. Its full time AWD. That means the computer checks the wheels like 200 times a second (depending on what car you have) to see if it slips or loose traction, etc. It then transfer power to wheels to keep the car going at where the driver wants it to. Most SUV now a days are AWD. Most sports car that runs on more then 2 wheels are AWD not 4WD.

4WD is you can manually adjust which wheels to drive the car. This is used for real offroad. You can set front wheels only, rear wheel only, or 4 wheels. In basic 4WD, it is usually rear wheel only or 4 wheels. But an expensive top line offroad vehicle that is 4WD lets you drive with front wheel power only as well.

There is an ON/OFF switch for 4WD but none for AWD.

This pretty much answer all lesnar questions besides the fuel efficiency part and I will state it here: Yes, 4WD/AWD will use more fuel then a 2WD car.

[baileyr]

I don't get your point. Yes I mention what cars have 4WD and what cars have AWD, but I did mention how AWD works (a computer sensor) vs 4WD works (drivers select which wheels to drive the car)


Bumping an old thread...

AWD does NOT mean that there are "computer sensors" involved.

The most basic AWD system would have three open differentials (front, centre and rear) and no computer involved or needed. Most early systems like this have some method of locking the centre diff, since it is quite easy to get stuck if you can't lock the centre. The early quattro systems also had a manually engaged solid lock for the rear diff as well, essentially becoming a "true" 3 wheel drive (both rear wheels and one front) when locked.

[kdholdom]

Just to clarify the Part Time 4 Wheel Drive System:

Part Time 4 Wheel Drive
This is the oldest system which the settings can be changed depending on your driving situation. With this system the four wheel drive CAN NOT be left engaged on pavement. The result will be necessary wear on mechanical parts. It costs quite a lot to replace your transfer case after it snaps because of Pavement four wheel driving. You have three settings 2WD, 4WD High, and 4WD Low. In 2WD it usually is the rear wheels that are working. In 4WD the torque gets distributed 25% to each wheel. When traveling around a corner the wheels have to travel different speeds but are linked together and forced to spin at the same speeds. As mentioned abve this puts a rather large strain on the transfer case. This type of system is best for people who go off-roading which is the reason this is the system of my choice.

[lh0628]

Subaru cars probably have way above average low end torques.

Most manual subaru cars have 50/50 F/R power split, some autos have 90/10 F/R power split, this changes when F/R tires spin at different rates, at which time the center differential comes in to work and changes the ratio.