AWD vs 4WD

rosscci

what is the difference between AWD vs 4WD?
6 B8 L# ^& O3 A% GThanks

我的天地

all wheel drive, four wheel drive.
' C9 L; X1 c" F* z+ k  \
awd, 如果你车子是8个轮子,那他们都驱动
/ E4 ?: S0 t3 A4 h( e9 Q! w6 O
4wd, 是如果你车子是8个轮子,那只有4个动.

rosscci

for cars with only 4 wheels, there is no difference between AWD and 4WD. Am I right?
0 J" J; o9 t6 T1 oThanks

newguy

4wd is selective. You can switch it to 2wd if you want.
- |, d8 n& k; Q2 {- `- Iawd is fulltime as it doesn't offer the option of switching to 2wd

highbury

8个轮？！

Zhujiaolian

原帖由 newguy 于 2008-11-24 12:24 发表
4wd is selective. You can switch it to 2wd if you want.
awd is fulltime as it doesn't offer the option of switching to 2wd

/ Z* Z$ v# h) t$ v& b6 V( [No, my 4WD does not have choice, always 4 wheels drive. Maybe some do.

shark27

AWD恒时四驱
( o  F) M- s9 U. [2 Y- A; o! R1 }+ o4WD可转换到2wd而且有低速分动器

Zhujiaolian

原帖由 shark27 于 2008-11-24 21:53 发表
AWD恒时四驱
4WD可转换到2wd而且有低速分动器

我车上标的是4WD可是没有转换功能呀，郁闷！

hippo

A simple explanation with techno-primer...
" i4 v& P( I' I, K' O
PRIMER:

1 Y, R2 ^6 B: z& ?As a car moves down the road in a straight line all wheels are moving at
the same speed.  As it takes a corner each tire actually has to move at a
9 f# @7 I* p$ Ldifferent speed (since each tire actually travels a different distance -
  [8 Z/ V* q! @* \( j0 [! cinsides less than outsides and back less than front).  This difference of
8 t* f5 V4 g% {* W& `speed must be accounted for. especially if all four wheels are to be
driven.

; a2 y6 h! |% J9 QEXPLANATION:

AWD can be used under any conditions without concern for drivetrain damage
or drivability problems.  The difference in tire speed is allowed for
+ D6 _* E6 L( _7 v& q9 s, NWITHIN the vehicle's drivetrain.
2 l+ k' n3 ]' k1 T3 m" s
+ J: y: r: E+ U. z) ~' R& g4WD requires that the vehicle be taken out of 4WD on dry pavement.  In this
case, the difference in tire speed is NOT allowed for within the drivetrain
/ J. Z. S3 @3 [7 M& {$ H  n5 i" aso must be accomodated EXTERNALLY by actually allowing the tires to slip
& t0 i: ?+ k% K/ ?5 h(like when on ice, snow, or mud).

& B! f! B/ I3 k" z$ V/ p+ w$ yDEEPER:

4 t0 z) N5 T: |In 4WD there is no center differential to allow for front to back speed
( u- Y$ N  u% I9 }' ]; ^) x$ W+ Xdifferences, in AWD there is.  Most good AWD systems also allow for
transmitting power to the wheels that have the most traction (a regular
) r1 k) R+ K& U7 \8 q1 uopen differential actually sends most of the power to the wheel with the
LEAST traction!).  Two good systems (my own judgement) are the viscous
" V: L- j1 a; a! t% V# rcoupling and the Torsen (torque sensing) - both work fine and are reliable.

shark27

原帖由 Zhujiaolian 于 2008-11-24 21:56 发表
" R/ O; Z! J6 `$ W
我车上标的是4WD可是没有转换功能呀，郁闷！

some marketing people dopped too much, they dont know the different between AWD and 4WD, or maybe they just want to build up a false ideas in your mind

Zhujiaolian

原帖由 shark27 于 2008-11-25 22:49 发表

5 g! x/ i) l+ x- t' D, ]
( U# ?3 P( H; ^" xsome marketing people dopped too much, they dont know the different between AWD and 4WD, or maybe they just want to build up a false ideas in your mind

  S3 Q6 O3 z4 g# H8 G& W* k看不太明白，车上的标志是原厂的标志，难道生产者也不知道吗？？？

CASH$$$

现在没什么区别了,4wd 和awd都是全时4驱.

shark27

原帖由 Zhujiaolian 于 2008-11-25 22:53 发表

看不太明白，车上的标志是原厂的标志，难道生产者也不知道吗？？？

mostly they knows well, just want to fool you and grab your money

放风儿

试着解释一下有关概念。

All wheel drive (AWD) 所有轮子同时得到动力（很多crossover车都是Auto AWD）
# i9 F. d% R. V% U' i, x0 W/ @1 \) lfull time 4WD  所有轮子永久得到动力，有些truck和suv有switch手动转换到2WD
( A) E! g7 X5 f1 t  e( Qpart time 4WD  正常情况下只有两个轮子驱动，只在traction loss的时候分配给另外两个轮子动力
Auto AWD 基本被认为是Part time 4WD
3 N' c9 _; @) p4-low 一般只在4WD的truck和SUV上有，4-low模式对车速有严格要求，不能过高（不同车具体看manu）。当4-low状态时，四个轮子得到最大的扭矩，在上陡坡，拖引trailer或载重大时有巨大帮助。
" S$ i, O7 \. \: R# r: v. q! @center differential 在4x4的truck和SUV中都有，也是我们常说的中央差速锁。即当汽车的一个轮打滑空转时，它能迅速锁死差速器，同时把大部分的扭矩甚至全部扭矩传给不滑转的轮子，充分利用它的附着力而产生足够牵引力，使汽车能够继续行驶。
9 i( M0 \0 ?; z& w, g$ u* j) z
( l$ v+ q, J8 _: }4 ?; q2 {0 Y综上所述：AWD（非part time AWD）和4WD在一般情况下无异，都是四个轮子同时得到动力，但真正意义的4WD或4x4有AWD车没有的4-low和center differential 。
不知解释清楚没有？

另外影响越野车越野性能和通过性能的还有底盘结构，悬挂方式，离地空间，轴距等。

MingJ

Full time 4WD, also called permanent 4WD, (not to be confused with: part time 4WD ) is a system that powers all four wheels at all times and can be used full time on all surfaces including pavement. The additional feature of a differential incorporated into the transfer case makes it possible to use 4WD all the time.
$ R. q0 q. ]# S+ r- h2 n2WD is not available (only part time 4WD offers that option). Each tire creates 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".
' C/ v7 N- Z0 b" m" j, @* Y$ tFull time 4WD vehicles work very well on-road and are very capable off-road.

5 Y- |# ~* O- B( u$ w$ lWhen "4-low" is selected the wheels create substantially more torque (on a Grand Cherokee its 2.72 times more) than in "4-high" - at the same time the vehicle moves at substantially slower speeds (2.72 times slower on a Jeep Grand Cherokee).

Important: "4-low" does not create more traction - it creates more torque and that can be detrimental when traction is marginal. Slipping tires are more likely in "low" than in "high"!
) L3 {1 G2 |; _2 @9 J1 m4 X( I
8 L/ B3 z- M' d1 g% |. cThe 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, when more torque and/or slower speed is needed.

2 A( n  m# @$ Y5 yAll wheel drive (AWD) is almost the same thing as full time 4WD - it is a system that powers all four wheels of a vehicle at all times as well. Full time symmetric AWD would be the best term to be used. Difference to full time 4WD is that a "4-low" setting is not available in AWD cars. Due to the lack of "low range" AWD vehicles are much less capable in off-road settings than full time 4WD vehicles, but work perfectly well on-road.

Automatic AWD system is the newest kid on the block. PR agency generated names like "Real Time 4WD", "intelligent AWD" or "active AWD" are hiding the fact that automatic AWD is essentially a sophisticated 2WD system. Automatic asymmetric AWD would be the best term for them.
& b1 p! Q! `# S; r- ]" K2 W
Here is how they work: Under normal conditions one axle gets 100% of the torque - meaning you are driving in 2WD. During traction loss at the driven axle (could be front or rear) a fully automatic system (hydraulic, mechanical or electronic) makes up to 50% of the torque to the axle with traction available. This means you have to lose traction in 2WD on your driven axle first and then the other axle will be added and try to keep the car moving and stable. Once the primary driven axle regains traction and both axles rotate at the same speed again, the system reverts back to 2WD. So, for a moment you had AWD.
6 Y. T, Z+ V# v4 B  d
: p* h! E! r4 m) ^8 \Automatic asymmetric AWD is much less capable in off-road settings than full time AWD systems and inferior to full time 4WD. However, automatic asymmetrical AWD is becoming more and more sophisticated and offers pretty much everything consumers expect for everyday (pavement) driving.
1 n+ W; ]* R9 `: x. i
0 `, y. d* x0 \7 \8 rExamples: Honda CRV, (newer) Toyota RAV4, LandRover Freelander, Isuzu Trooper (TOD), Volvo V70, 1999 and later Jeep Grand Cherokee (in high range).
' z. J& T1 `, a- m# e/ ?6 S
/ _0 p- ^: Z9 |5 g! |" WRecently some magazines have called the automatic AWD system "part time 4WD", since it offers AWD only part of the time. They have a point - however, the term "part time 4WD" has been used since WW II for cars like the Willys and Jeep Wrangler and their part time 4WD . A manual system where the driver had to select 2WD or 4WD. The name coming from the fact that 4WD was designed to be used only part of the time (when off-road), most of the time it had to operated in 2WD (on-road).

A center differential is essential for on-road use but can be detrimental for off-pavement use. When leaving pavement the center differential needs to be disabled (locked). It either locks automatically* or it has to be locked (disabled) manually