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> AWD And 4WD
Nomake Wan
Posted: Mar 19 2005, 08:10 AM


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Now, what really throws a crazy wrench into the mix is what you would consider AWD. I have absolutely no idea how any 4WD/AWD systems work except those in Subarus. And merely in that category...

...there are older cars, like the XT6, which had what Subaru called "Push-Button AWD." By your definition, this is actually 4WD since it has to be activated. Then, you have the first-generation Subaru Legacy, which introduced AWD, ABS, the Boxer engine and a crapload of other ahead-of-its-time stuff. However, the AWD system in these first cars was not all that advanced. For instance, the system employed with the 4EAT (Automatic) sends 10% power to the rear and 90% power to the front. In essence, the car handled much like a FWD except in certain situations where the front tires slipped, in which case there was support power from the rear transaxle. The manual transmission sent a 50/50 split if I'm remembering my facts correctly. Therefore, what is the 4EAT's system, since it is essentially a power-assisted FWD?

The newer Subaru systems (as shown by DGoReck) are a hell of a lot more advanced, and as seen, are by your definition true AWD systems. It's still interesting that there's such a big difference between power distribution systems in manual and automatic Subarus.

Yeah, that's all I've got to really contribute. I always thought that the difference between 4WD and AWD was a mere marketing gimmick, but since there are systems where all of the wheels aren't powered all of the time, I think it's safe to use one of them to describe that system. That is... as long as everybody else on the planet knows what the hell you're talking about. ^_~
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VRr1FD
Posted: Mar 20 2005, 08:16 PM


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subaru - the beauty of 4 wheel drive. wink2.gif
WRX DEMON Type R
Posted: Mar 20 2005, 09:57 PM


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Subaru - The all time leader (?) in All-Wheel-Drive.
Frost
Posted: Mar 20 2005, 10:18 PM


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I'm not too sure of that.... lot's of people are doing AWD now and the father of the damned thing is Audi so Subby can't be the all time leader in it since Audi lead the way back in the late 80s.

Right now I'm dying to get my hands on the Acura's SH-AWD.

Frost
Sti_Brumby
  Posted: Mar 20 2005, 11:27 PM


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Cough leone Rx subaru 80 model is awd..
InitialN00b
Posted: Mar 20 2005, 11:37 PM


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Audi had it since the early 80s

Well, the first to seriously put some thought into it at least.
Frost
Posted: Mar 21 2005, 02:02 PM


Time to slam into 2nd gear!
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Ironically, the skeptics back then against Audi said AWD = 4WD and that it would never work in the rally scene. Someone bet on the wroooong side.

Frost
WRX DEMON Type R
Posted: Mar 21 2005, 04:32 PM


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I agree with you guys on the Audi = father of awd thing.

I was confused that Subaru ad said "All Time leader in AWD".
InitialN00b
Posted: Mar 21 2005, 05:04 PM


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QUOTE (Frost @ Mar 21 2005, 06:02 PM)
Ironically, the skeptics back then against Audi said AWD = 4WD and that it would never work in the rally scene. Someone bet on the wroooong side.

Frost

Indeed

It did take them a season to really develop it before they started mopping the floor with people's asses laugh.gif
sideways
Posted: Mar 21 2005, 05:11 PM


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When awd first came out it didnt really make a huge denti n the rally scene- they performaed awesome but it was still developing, often theyd break before they could finish- it wasnt until technology caught up and they could make them lighter/stronger did you really see them pwning' the dirt

This post has been edited by sidewaysgts on Mar 21 2005, 05:11 PM
Frost
Posted: Mar 22 2005, 06:42 AM


Time to slam into 2nd gear!
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Actually it did make a huge dent in the rally scene because they were just beginning to move from RWDs to FWDs. Audi came about and changed all that with the AWD idea. While granted it didn't sweep the standings in the first season due to technical problems (tell me what new technology never had startup problems), when it did finish, it finished way ahead of the competition and that was enough to shut up ALL the critics who suddenly began getting pink slips for not thinking outside the box.

Hence back to the AWD and 4WD arguement. 4WD is great and all but AWD is a whole new ball game.

Frost
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Posted: Mar 22 2005, 07:26 AM


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QUOTE (Frost @ Mar 22 2005, 09:42 AM)
Hence back to the AWD and 4WD arguement. 4WD is great and all but AWD is a whole new ball game.

Frost

I like this sentence very much. happy.gif
Sti_Brumby
  Posted: Apr 6 2005, 05:07 PM


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All Wheel Drive (AWD): Most cars are front wheel drive, some are rear wheel drive.
That means that either the front or rear axle is powered and usually only one wheel.

All Wheel drive means that instead of either front or rear, both axles get power from the engine. This means that your Subaru is being pushed and pulled by all four wheel at the same time resulting in far superior traction in all driving conditions.

Subaru's all-wheel-drive is intended for everyday driving, detects any loss of traction and adjusts instantly in all situations including emergency braking, hard cornering, rain or snow slick roads with a substantial improvement in driver control and safety.
In other words... it's great.

Subaru All Wheel Drive (AWD). There are 3 systems- Continuous, Active and VTD


The types of all wheel drive used are:

Continuous AWD: Subaru manual transmissions use Continuous AWD, normally 50/50 front-to-back power split and use a mechanical viscous center differential to to vary the power split when there is a loss of traction.

Active AWD: Subaru's automatic transmission use Active AWD, mostly front wheel drive and uses traction sensing computer input to electronically vary the front to rear power split via a hydraulic multi-plate transfer clutch.

VTD AWD (variable torque distribution). New in 2001, VTD transfers powers front to back electronically. The power split is 45/55 front/rear and the rear wheel bias is designed for a more luxury car feel as opposed to the front bias of the Active AWD system. Usually 45/55 front to back split but that varies according to wheel slippage.

Personally i think subaru are the leaders in AWD systems They would have to be as every car they make now has it!

This post has been edited by Sti_Brumby on Apr 6 2005, 05:12 PM
AP1
Posted: Apr 12 2005, 01:10 PM


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This explains everything, we have a 4WD Highlander and my Dad hasbeen asking me what 4WD is. All I know is that the power go to all 4 wheels. blink.gif
Nd4SpdSe
Posted: Apr 12 2005, 03:12 PM


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I started to type stuff out, but i ended up doing some research, this explains it best:

4WD vs. AWD: Which is best for you?

Although the terminology is often used interchangeably, four-wheel drive (4WD) and all-wheel drive (AWD) are different types of systems with different pros and cons. The type of vehicle that's best for you depends on the conditions you typically face.

AWD continuously powers all four wheels and provides maximum traction in all driving conditions. It's especially helpful in wintry conditions and when driving in moderate off-road terrain. All AWD systems are full-time, so there's no need for a driver to manually shift into AWD mode. Its lightness and compactness makes AWD the system of choice for wagons, minivans, and an increasing number of SUVs, particularly car-based models.

The key difference between 4WD and AWD is that 4WD uses low-range gearing, which helps in challenging off-road conditions such as traversing rocks, steep slopes, or deep water. The vast majority of 4WD-vehicle owners, however, rarely need this capability. In addition, 4WD systems are typically heavier, which compromises fuel economy.

Most modern 4WD systems are full-time. But part-time systems are found on many pickups and traditional SUVs. These require the driver to manually shift between two- and four-wheel drive, and the vehicle can't be driven on dry pavement when in 4WD mode.

Cubits
Posted: Apr 12 2005, 09:36 PM


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Why can't the vehicle be driven on dry pavement in 4wd mode? I drive my pajero on dry pavement in 4wd mode, but usually don't because of fuel economy and power loss issues. Maybe the can't would be better as shouldn't?

4wd can easily be single range (we call it single/dual range), but isn't common. Single range 4wd was only really seen on lightweight/car applications.

The key difference is AWD systems use torque sensing diff's to redistribute the torque to each wheel seperately, while 4wd systems have fixed torque distribution.
sideways
Posted: Apr 12 2005, 09:41 PM


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I thought driving on the road with 4wd engaged was hard on the difs and would break em easy? what ive been told at least, never thought much about it
Nd4SpdSe
Posted: Apr 13 2005, 04:41 AM


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This is why:

http://www.4x4abc.com/4WD101/axle-wind-up.html

Related article on why not:
http://www.4x4abc.com/4WD101/def_turnpart.html

Unless your Pajero's sytem is Full-Time 4WD
http://www.4x4abc.com/4WD101/def_turnfull.html

This post has been edited by Nd4SpdSe on Apr 13 2005, 04:44 AM
Cubits
Posted: Apr 13 2005, 05:20 AM


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Aaah, it's actually both. The transfer case has 2wd and 4wd modes with a lockable central diff, so it can operate as 4wd on pavement fine, just not with the diff locked.
AP1
Posted: Apr 13 2005, 05:43 AM


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Wait, I don't get it, why can't it be driven on dry pavement when in 4WD?
Cubits
Posted: Apr 13 2005, 05:59 AM


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Because in a turn the front wheels trace a wider arc than the rears, so the front wheels have to spin faster (more distance = more rotations).

Unfortunately, in 4wd's without a centre diff, the front and rear wheels are forced to spin the same speed, which means something has to give. In low grip conditions, it's usually the rear tyres that slip, but on a good grippy surface the drivetrain will fail first.

This post has been edited by Cubits on Apr 13 2005, 05:59 AM
Nd4SpdSe
Posted: Apr 13 2005, 06:46 AM


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QUOTE (Cubits @ Apr 13 2005, 05:20 AM)
Aaah, it's actually both. The transfer case has 2wd and 4wd modes with a lockable central diff, so it can operate as 4wd on pavement fine, just not with the diff locked.


Shouldn't make a difference if it's locked or not, a locked diff just prevents the tire with less traction to get all the power. Like rock climbers, sometimes they have1 or 2 wheels in the air, they use a locked diff so all tires move at the same time, otherwise the tire in teh air will get all the power, and they couldn't move. On a paved surface, since the tires can't slip, they have to move at the same time, and like you said, since the outter tire moves faster than the inner tire, and with (caution, double negative) no lack of traction, the diff will be strained and can pop or break.


This post has been edited by Nd4SpdSe on Apr 13 2005, 06:55 AM
Cubits
Posted: Apr 13 2005, 07:08 AM


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I think you're confusing the front and rear diffs with the centre diff.

I can lock the centre diff to transfer torque evenly front/back, but the left/right transfer is still open (although the rear has a viscous lsd). If i put a front wheel in the air with the centre diff open the car won't move. Having it closed will force the rears to drive despite the front being airborne.

This is why top end offroaders have lockable front/rear diffs or run the more durable spool diffs, so you can rock-crawl and essentially drive with one wheel.
LanEVOchris
Posted: Apr 14 2005, 07:34 PM


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4wd or four wheel drives are cars that run on 4 wheels. Unlike FF or FR or MR or RR, it has a faster pickup and more torque.But 4wd consumes a lot of petrol.
In Malaysia, most 4wd run on diesel and are equipped with turbo intercoolers.
Overall, 4wd are the best. Cars like Skyline, EVO, Impreza and H2 are fast because they are 4wds
sideways
Posted: Apr 14 2005, 08:04 PM


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^--- rolleyes.gif

awd has the advantage off the line IF your making some good power, this is because 2wd cars will spin their tires easy and awd has more chances to have forward traction, after this- awd is dead weight. Awd CAN also have advantages with accelerating abilities on corner exit.

HOWEVER awd (and ff) have "limited lines". Basicly theyre going to understeer pretty good on exit, just think about traction circles and its clear why. This is a big reason why rwd vehicles do well in competitive head-head racing.

Lastly, whats his awd has "more torque" deal? Generaly speaking, awd drivetrains are much heaver and theres more for the power to go through; to be blunt awd has (Generaly) the highest drivetrain loss %, with Frs being next, and ff/mr/rr (transverse 2wd vehicle) being last.

This post has been edited by sidewaysgts on Apr 14 2005, 08:06 PM

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