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Old 01-15-2005, 11:08 AM   #1
daan
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Default Impreza (or Subaru) AWD vs. CRV AWD

Hi all,

Just out of curiosity, I had a question which I could find the answer to. What is the difference between the above AWDs. Is it that the CRV is normally two wheel drive and it distributes power to the rear once it slides and the Impreza's all wheel drive is normally on all the time and it distributes more power to the specific wheel. Thanks.
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Old 01-15-2005, 12:33 PM   #2
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Quote:
Originally Posted by daan
Hi all,

Just out of curiosity, I had a question which I could find the answer to. What is the difference between the above AWDs. Is it that the CRV is normally two wheel drive and it distributes power to the rear once it slides and the Impreza's all wheel drive is normally on all the time and it distributes more power to the specific wheel. Thanks.
CR-Vs are not AWD unless they changed it recently, CR-V is RT-4WD. There is no locking centre diff to make it AWD. and you are right, CR-Vs are usually in 2WD until there is slippage, then the rear wheel gets power. Not sure about the current generation CR-Vs but the old ones actually takes a bit of time to switch to 4WD.
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Old 01-15-2005, 01:03 PM   #3
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An automatic impreza is also "RT-AWD" the normal distribution is 90 front and 10 rear, so on a wet day with bad tires (ie: stock), full throttle and you can get the front wheels spinning and then there'd be a second of waiting before the awd "kicks in" to 50:50... the full time AWD is only on the manuals where there's a consistent 50:50 distrubution

I used to own an auto impreza and that's what it felt like... very inconsistent and quite unpredictable, since it works this way you can easily snap-oversteer... pretty scary if you ask me
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Old 01-15-2005, 01:15 PM   #4
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Quote:
Originally Posted by ashtaron14
An automatic impreza is also "RT-AWD" the normal distribution is 90 front and 10 rear, so on a wet day with bad tires (ie: stock), full throttle and you can get the front wheels spinning and then there'd be a second of waiting before the awd "kicks in" to 50:50... the full time AWD is only on the manuals where there's a consistent 50:50 distrubution

I used to own an auto impreza and that's what it felt like... very inconsistent and quite unpredictable, since it works this way you can easily snap-oversteer... pretty scary if you ask me
interesting..... I didnt know that auto arent really full-time AWD
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Old 01-15-2005, 01:37 PM   #5
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yeah it's pretty weird...
i was playing donnuts in my car and in my friend's 04 TS wagon...while in my car i can do perfect drifting around the pole (counter steering all the time), in his car sometimes i have to use handbrake to induce oversteering while so other times it just suddently go oversteering...not very predictable and less control...
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Old 01-15-2005, 01:38 PM   #6
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I thought all Subarus are AWD doesnt matter what their tranny is, but really interesting to find out.

March
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Old 01-15-2005, 01:52 PM   #7
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Yeah this is a fun discussion.. Now can we get someone with authority on the subject to make an appearance?

I've heard things that vary between the model 50:50, 40F:60R (WRX?), 60F:40R (RS/TS?), 90F:10R .. and newer STi are totally variable between 40:60 and 60:40 ? It's hard to keep track of it all.
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Old 01-15-2005, 01:55 PM   #8
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general speaking
all manual WRX/RS/TS = 50:50 all the time
all auto WRX/RS/TS = 90:10 all the time
STI w/ VCD = i'm not sure...somebody help me out~
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Old 01-15-2005, 01:59 PM   #9
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Quote:
Originally Posted by anonymous_wolf
...
all auto WRX/RS/TS = 90:10 all the time
Not exactly. 1st gear - locked 50:50, second gear - locked 50:50 as well, third and fourth is 90:10 by default, switches to 50:50 when accelerating and everytime when the wheel spin detected.

So it's not that bad after all. You _can_ do donuts in an auto TS
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Old 01-15-2005, 02:28 PM   #10
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really?!
i didn't know that...
so i guess it is the rear LSD that makes my car easier to do donuts~
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Old 01-15-2005, 02:47 PM   #11
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Quote:
Originally Posted by jackwei
CR-Vs are not AWD unless they changed it recently, CR-V is RT-4WD. There is no locking centre diff to make it AWD. and you are right, CR-Vs are usually in 2WD until there is slippage, then the rear wheel gets power. Not sure about the current generation CR-Vs but the old ones actually takes a bit of time to switch to 4WD.
I'm not sure why you said CRV's are not AWD. AWD doesn't necessarily mean full time AWD. If something can send power to all of its 4 (or 6, or 8...) wheels, it's AWD.

Along your line of argument, does this mean an older 4Runner/Grand Cherokee and the like are not AWD because it requires a manual lever (or button) to select the all wheel drive mode?
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Old 01-15-2005, 03:09 PM   #12
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Quote:
Originally Posted by -S-
Along your line of argument, does this mean an older 4Runner/Grand Cherokee and the like are not AWD because it requires a manual lever (or button) to select the all wheel drive mode?
Exactly, those vehicles are considered 4WD, not AWD. Generally the distinction between 4WD and AWD has been 4WD requires user action to engage it (often a hi-lo transfer case), and there is usually no center diff. AWD means all the wheels are driven all the time and because of this AWD cars do require a center diff (otherwise you couldn't turn tight corners). I'd argue that real time switching systems like CR-V's and Subaru's 4EAT are much more like AWD since the switching basically acts like an electronic center differential.

Locking center diff has nothing to do with AWD/4WD. As I mentioned, most 4WD vehicles have no center diff, but all AWD vehicles do have one. Some AWD vehicles have locking center diffs to help in situations with extremely low traction. An AWD vehicle with open diffs would get stuck if only one wheel had zero traction but with a locked center diff, you need one front and one rear wheel to have zero traction. Add a rear diff lock and now you need both rears and one front to have no traction to get stuck.
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Old 01-15-2005, 03:10 PM   #13
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DCCD can change the ratio of % power to the front or rear wheels. Extreme's are 90:10, 10:90; 50:50 for normal I guess. Yeppers only in 1st and 2nd gear in a auto ts or rs can 50:50 be active at all times, its pretty much the best way to make nice tight donuts or figure eights in the snow. No clue as to whether the wrx's are the same. Anyone want to clue in on this? Is the wrx auto tranny in respects to % distribution the same that of the rs or ts?
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Old 01-15-2005, 03:41 PM   #14
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errr... not exactly... for WRX's it's 45/55 split
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Old 01-15-2005, 03:44 PM   #15
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Quote:
Originally Posted by OnlyKor..
errr... not exactly... for WRX's it's 45/55 split
For 45/55 with automatic and 40/60 for STD? .. I was told I have a 40/60..
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Old 01-15-2005, 04:00 PM   #16
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so auto subarus have a 90:10 distribution until the car senses a lost of traction?? that applies to all 4 gears on an auto wrx?
i drive an auto myself and now that i know about the distribution differences, at times i did feel that the car's AWD kicks in when i am starting to lose traction on my rear wheels, but i just thought how RT-AWD would work anyways?
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Old 01-15-2005, 04:24 PM   #17
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Quote:
Originally Posted by ashtaron14
An automatic impreza is also "RT-AWD" the normal distribution is 90 front and 10 rear, so on a wet day with bad tires (ie: stock), full throttle and you can get the front wheels spinning and then there'd be a second of waiting before the awd "kicks in" to 50:50... the full time AWD is only on the manuals where there's a consistent 50:50 distrubution

I used to own an auto impreza and that's what it felt like... very inconsistent and quite unpredictable, since it works this way you can easily snap-oversteer... pretty scary if you ask me
that's not correct. RT-4WD has 0 percent to the rear when there is no slippage. AWD means that there is a locking centre differential, the CR-V does not have one and the AT subarus do.

your fronts were spinning because the diff has not locked yet. on a CR-V the centre diff WILL NOT LOCK. so if one wheel slips on the CR-V, only that wheel will spin since all the differentials are open. If you AT Subaru has a rear LSD, at least 3 wheels will spin no matter what once the diffs are locked.... 2 if it doesn't have a rear LSD.
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Old 01-15-2005, 04:29 PM   #18
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Quote:
Originally Posted by AllWheelDrift
Exactly, those vehicles are considered 4WD, not AWD. Generally the distinction between 4WD and AWD has been 4WD requires user action to engage it (often a hi-lo transfer case), and there is usually no center diff. AWD means all the wheels are driven all the time and because of this AWD cars do require a center diff (otherwise you couldn't turn tight corners). I'd argue that real time switching systems like CR-V's and Subaru's 4EAT are much more like AWD since the switching basically acts like an electronic center differential.

Locking center diff has nothing to do with AWD/4WD. As I mentioned, most 4WD vehicles have no center diff, but all AWD vehicles do have one. Some AWD vehicles have locking center diffs to help in situations with extremely low traction. An AWD vehicle with open diffs would get stuck if only one wheel had zero traction but with a locked center diff, you need one front and one rear wheel to have zero traction. Add a rear diff lock and now you need both rears and one front to have no traction to get stuck.

WRONG. Look up the definition, I have a book here that says otherwise, you can come read it if you like. AWD is 4WD with a locking centre differential.
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Old 01-15-2005, 07:36 PM   #19
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no no ! 4eat is 45/55 front/rear !! better than manual 50/50 !!
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Old 01-15-2005, 07:46 PM   #20
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Quote:
Originally Posted by jackwei
WRONG. Look up the definition, I have a book here that says otherwise, you can come read it if you like. AWD is 4WD with a locking centre differential.
What's the title and whose the author of the book?

Quote:
By AWD
Generally the distinction between 4WD and AWD has been 4WD requires user action to engage it (often a hi-lo transfer case), and there is usually no center diff.
[emphasis by me]
AWD's general statement above is regarding PART TIME 4WD vehicles (such as older 4WD SUV's, pickups, and other vehicles. The "part time" is due to the fact that to get "all 4 wheels" going, you need to use the transfer case to connect power to the front wheels. Usually these transfer cases mearly lock the front-and-rear drivetrains together and do not have a centre differential.

Quote:
By AWD
...Some AWD vehicles have locking center diffs to help in situations with extremely low traction...
Again, another general (yet correct) statement by AWD.

Quote:
Taken from www.rallycars.com
A full time 4WD performance car, as mentioned earlier, needs 3 differentials in order to operate properly.
In general, "full time 4WD" is better known as "all wheel drive". Without the centre differential, the vehicle would handle terribly due to the fact that the front AND rear wheels would in essence have to turn at the same speed. Not a problem with these (part-time) 4WD vehicles since usually it's in 4WD mode in snow, on dirt, in the mud, etc. Rarely would they been in 4WD mode on pavement.

The purpose of the "locking" centre differential is to have the best of both worlds. 1) The ability to have the front-and-rear wheels spin at different speeds for handling. (Have you driven a 2WD car with no differential? Why don't they make a 2WD car with no differential? It'd handle better in a straight line, but turning (slow turning especially) would be a real PITA). 2) The ability to lock and transfer power to both ends for better traction.

I hope you've enjoyed this lesson and discussion on AWD/4WD and the many variations of it. Tune in tomorrow, where we'll learn why we need to put oil in the frying pan AND in the engine, and why they're different.

LaterZ!
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Old 01-15-2005, 07:59 PM   #21
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Quote:
Originally Posted by jackwei
that's not correct. RT-4WD has 0 percent to the rear when there is no slippage. AWD means that there is a locking centre differential, the CR-V does not have one and the AT subarus do.

your fronts were spinning because the diff has not locked yet. on a CR-V the centre diff WILL NOT LOCK. so if one wheel slips on the CR-V, only that wheel will spin since all the differentials are open. If you AT Subaru has a rear LSD, at least 3 wheels will spin no matter what once the diffs are locked.... 2 if it doesn't have a rear LSD.

I'm not sure about the R(eal)T(ime) AWD system on the CRV. My wife has one, but I haven't played with it in the snow just yet. I do believe it's mainly FWD until slippage, then the drivetrain clunks into place to get power to the rear wheels. And if the centre diff doesn't transfer any power to the rear, then why get an RT CRV at all? Might as well stick with FWD which Honda does pretty well with.

I'd have to disagree with you with respect to the Subaru AT "centre diff". Not all AT's have them.

I've got my MY05 Subaru Legacy catalogue in front of me right now. In the specs section at the back it says:

Quote:
4-speed AT better known as the 4EAT
Electronically controlled multi-plate transfer case
No mention of a centre diff here.

But with the new 5EAT:
Quote:
5-speed AT (a.k.a. 5EAT)
VTD with lateral g-sensor AND an electronically controlled locking centre diff.

How does the 4EAT get away with not having a centre diff? Well, the electronically controlled transfer case basically acts as a "torque converter" [for the lack of a better word] that allows the two ends of the drivetrain spin at different speeds, much like a differential, but without all the gearing inside.

LaterZ!
Darren!!
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Old 01-15-2005, 08:16 PM   #22
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Well I heard that All-Wheel Drive is a term registered by Subaru, but they just never mind other brands using that name, correct me if I'm wrong.

Then for Subaru, the term All-Wheel Drive is not only a matter of the diffs., but it also includes the boxer engine (which lowers the centre of gravity), the different varieties of transmission (in AT the centre diff is included in the transmission), and the symmetrical layout. Now it might even includes VDC, or other means traction control.

At least that's what I found from their brochures ^_^. So if u ask what's the differeces between the CR-V and Subaru's AWD, u might as well think about the engine.

That's just what I found, correct me if I'm wrong.
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Old 01-15-2005, 08:29 PM   #23
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I think that's Subaru's catch phrase for 'Symmetrical AWD' for including the boxer engine AND the AWD layout. AWD has nothing to do with the engine. Heck, the Carrera4 (or whatever the AWD 911 model is called) has the boxer engine BEHIND the rear wheels!

LaterZ!
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Old 01-15-2005, 11:41 PM   #24
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Quote:
Originally Posted by jackwei
WRONG. Look up the definition, I have a book here that says otherwise, you can come read it if you like. AWD is 4WD with a locking centre differential.
Well then by your defintion, 90% of vehicles sold as AWD aren't AWD.

Maybe I should sue Subaru because they claim my TS is AWD (5mt) but it doesn't have a locking center diff.
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Old 01-15-2005, 11:57 PM   #25
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BTW, if anyone wants to know more about AWD and 4WD, including differentials etc, they can read these links:

http://auto.howstuffworks.com/four-wheel-drive.htm

http://mozart.chat.net/~jeske/unsoli...egacy/awd.html
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