4wd Vs Awd
09-03-2003, 10:16 AM
#1
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Anyone else notice in GT3 that all the cars that are AWD are listed as 4WD? Why is this? I've noticed that the Japenese don't differentiated between 4WD and AWD (Eg the Skyline GT-R is listed as a 4WD car in Japan).
I know the differences mechanically, and its clear that AWD and 4WD aren't the same (at least in my head). So how can you call one by the wrong designation?
I know the differences mechanically, and its clear that AWD and 4WD aren't the same (at least in my head). So how can you call one by the wrong designation?
09-03-2003, 10:53 AM
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I think in the case of GT3, they just say 4WD because some people call AWD 4WD.
It's actually different, I call them both the same, but it confuses people...:
Jeep was one of the first with a 'Full Time' 4 wheel drive system called 'QuadraTrac'. The system works great, nothing to touch.. always in 4WD. A center differential (Which really makes it AWD since the center diff is what AWD cars use to compensate for turning) allowed the front axle wheels to move seperately from rear wheels.
By defination Four Wheel Drive and All Wheel Drive are the same thing, since cars all have 4 wheels. In the sixties, International (Scout) called their four wheel drives, 'all wheel drive' to be different from Jeep.
Modern terminology used by today's car companies uses 'All Wheel Drive' (AWD) to denote full time systems (Audi, Subaru, etc.). Part Time systems are more like original 4WD, ie. back tires normal driving, front and back tires off road driving.
Part time systems may have 'shift on the fly' (engage while moving) and/or automatic locking hubs. Locking hubs on the front wheels, reduces wear during normal driving (2WD). Automatic hubs eliminate the need to get out and manually lock both hubs before using 4WD.
Examine all features from each company. All time 4WD and AWD are the same thing (always in four wheel drive or able to transfer power to any wheel), but each company has different features. If you want the ability to crawl slowly or climb steep grades, then make sure the AWD or 4WD system has a 'Low Range' (or 'two speed transfer case') the Subaru AWD system does not, their former part time system did.
It's actually different, I call them both the same, but it confuses people...:
Jeep was one of the first with a 'Full Time' 4 wheel drive system called 'QuadraTrac'. The system works great, nothing to touch.. always in 4WD. A center differential (Which really makes it AWD since the center diff is what AWD cars use to compensate for turning) allowed the front axle wheels to move seperately from rear wheels.
By defination Four Wheel Drive and All Wheel Drive are the same thing, since cars all have 4 wheels. In the sixties, International (Scout) called their four wheel drives, 'all wheel drive' to be different from Jeep.
Modern terminology used by today's car companies uses 'All Wheel Drive' (AWD) to denote full time systems (Audi, Subaru, etc.). Part Time systems are more like original 4WD, ie. back tires normal driving, front and back tires off road driving.
Part time systems may have 'shift on the fly' (engage while moving) and/or automatic locking hubs. Locking hubs on the front wheels, reduces wear during normal driving (2WD). Automatic hubs eliminate the need to get out and manually lock both hubs before using 4WD.
Examine all features from each company. All time 4WD and AWD are the same thing (always in four wheel drive or able to transfer power to any wheel), but each company has different features. If you want the ability to crawl slowly or climb steep grades, then make sure the AWD or 4WD system has a 'Low Range' (or 'two speed transfer case') the Subaru AWD system does not, their former part time system did.
09-03-2003, 11:34 AM
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I thought the difference was that 4WD has a mechanical transfer case where the axles are locked by gears (50/50), and AWD has a viscous mechanical, or electronic differential that split torque. Or are we saying the same thing?
If that's the case then how can a car without a geared transfer case be 4WD as the Japenese call it? Eg Skyline.. and the many Japenese Subaru commercials I've seen that say "4WD".
If that's the case then how can a car without a geared transfer case be 4WD as the Japenese call it? Eg Skyline.. and the many Japenese Subaru commercials I've seen that say "4WD".
09-03-2003, 12:54 PM
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Originally Posted by Baldy' date='Sep 3 2003, 12:15 PM
what's the deal with suv's that have "AWD," in which it drives in 2WD, then switches to 4WD automatically when the car deems necessary? How's that work?
Well, now that I think about it.. they could do this electronically too. Gauges montior the same shear stresses I talked about above and electronically engage the front drivetrain to kick in. Electronic AWD is usually a little bit faster than viscous/mechanical AWD, but I don't l ike it as much.
09-03-2003, 01:05 PM
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Originally Posted by kkw4p' date='Sep 3 2003, 09:54 AM
That's usually done with a viscous coupling known as the center differential. Works just like a viscious limited slip diff. If there's shear (from the two axles not traveling at the same speed) the fluid binds up (forms a concrete like paste) that forces the front and rear drivetrains to turn at the same speed. Pretty neat actually.
Well, now that I think about it.. they could do this electronically too. Gauges montior the same shear stresses I talked about above and electronically engage the front drivetrain to kick in. Electronic AWD is usually a little bit faster than viscous/mechanical AWD, but I don't l ike it as much.
Well, now that I think about it.. they could do this electronically too. Gauges montior the same shear stresses I talked about above and electronically engage the front drivetrain to kick in. Electronic AWD is usually a little bit faster than viscous/mechanical AWD, but I don't l ike it as much.
mike
09-03-2003, 02:06 PM
#9
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All-Wheel Drive - All-wheel drive offers the best of both worlds. In an all-wheel drive system, power is distributed to all four of the vehicle's tires, all of the time. Subaru and Audi have built their reputations on all-wheel-drive sedans and wagons. All-wheel drive passenger vehicles handle better than most front- AND rear-wheel drive vehicles. Both 4WD and AWD improve traction for moving on ice and snow, but they don't do anything for stopping ability. For that reason, they can build a false sense of security that leads drivers to follow too closely.
Four-Wheel Drive - Many SUVs offer all-wheel drive as an option, with four-wheel drive as standard equipment. In a four-wheel drive system, power is delivered to all four wheels, only when the driver requests it. In normal use, four-wheel drive vehicles operate on rear-wheel drive. If additional traction is required, the driver flips a lever that switches the transaxle from two-wheel (rear) drive to four-wheel drive. This system is useful for off-road vehicles, snow plows, and tow trucks. Both 4WD and AWD improve traction for moving on ice and snow, but they don't do anything for stopping ability. For that reason, they can build a false sense of security that leads drivers to follow too closely.
Four-Wheel Drive - Many SUVs offer all-wheel drive as an option, with four-wheel drive as standard equipment. In a four-wheel drive system, power is delivered to all four wheels, only when the driver requests it. In normal use, four-wheel drive vehicles operate on rear-wheel drive. If additional traction is required, the driver flips a lever that switches the transaxle from two-wheel (rear) drive to four-wheel drive. This system is useful for off-road vehicles, snow plows, and tow trucks. Both 4WD and AWD improve traction for moving on ice and snow, but they don't do anything for stopping ability. For that reason, they can build a false sense of security that leads drivers to follow too closely.
That's from Smart Motorist.
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