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the difference between Four Wheel Drive (4WD) and All Wheel Drive (AWD)
Originally posted by heartbroke2 at 2004-12-6 01:28 AM:. j; \6 d4 d- s
4WD和AWD有什么区别？向阳花介绍一下。
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Full time four wheel drive (not to be confused with: part time 4WD ) is a system that powers all four wheels at all times. Each tire gets about 25% of the available torque when the ground is level with a consistant surface. Driver has a choice of a "4-high" (that's your every day setting) and "4-low".
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When "4-low" is selected the wheels receive substancially more torque (on a Grand Cherokee its 2.72 times more) than in "4-high" - at the same time the vehicle moves at substancially slower speeds (2.72 times slower on J GC).3 T. N2 v' z( W, t. R
- Y0 j& M5 e, J& K a$ zThe low setting is an advantage for drivers who need to tow and maneuver a heavy trailer etc and for drivers who at one point or another may want to negotiate difficult off-road terrain.
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2 F% r9 l# ^) @0 B7 oAll wheel drive is a system that powers all four wheels of a vehicle at all times as well. Difference to full time 4WD is that a "4-low" setting is not available. Due to the lack of "low range" AWD vehicles are much less capable in off-road settings than 4WD vehicles.
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2 p- a. O7 g1 e: pRecently some new "automatic" AWD systems have emerged. Fancy names like "Real Time 4WD" are hiding the fact that they are essentially sophisticated 2WD systems. They should be called part time AWD systems. They cannot claim the same (minimal) safety and traction advantages of full time 4WD. They are much less capable in off-road settings than full time AWD systems and inferior to full time 4WD. However, automatic AWD is becoming more and more sophisticated and offers pretty much everything consumers expect for everyday (pavement) driving.
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?4 @' X# _; v" | H* KHere is how they work: During traction loss on the driven axle (could be front or rear) a fully automatic system (hydraulic, mechanical or electronic) routes torque to the axle with traction. This means you have to completely lose traction in 2WD on your driven axle first and then the other axle will take over and try to keep the car moving. So, for a moment you have 4WD (AWD). Doesn't mean much because only two wheels have traction. Once the driven axle regains traction and both axles rotate at the same speed again, the system moves back to 2WD.% u$ S% u/ J3 d$ \. @. \3 o, t- M- V! ~
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A consumer complaints about automatic AWD is that all 4 tires need to be replaced." X. P, k$ J6 Z$ E R
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Examples: Honda CRV, LandRover Freelander, Isuzu Trooper (TOD), Volvo V70, 1999 Jeep Grand Cherokee (in high range)
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6 q* J( X6 u/ C4 L1 fSome vehicles have a combination of part time and full time 4WD
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9 u- ~) y1 w. p7 |% _0 v[ Last edited by 社员都是向阳花 on 2004-12-6 at 03:11 PM ] |
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发表于 2004-12-5 04:34
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