Can someone explain how AWD works with an open differential?
01-07-2003, 03:32 PM
#1
Guest
Posts: n/a
Can someone explain how AWD works with an open differential?
This is my first post!!!!!!!!!!!!!!!!!!!!
Anyway, I currently own an Outback and I'm thinking about purchasing a WRX.
I know my Outback has a limited slip rear differential, and also that the WRX has one but the 2.5RS does not.
So far so good. This is were I get confused. How does AWD transfer power "from the wheels that slip to the wheels that grip" if there is an open differential in the front, and in the case of the 2.5 RS and other Subarus which don't have a LSD in the rear?
An open differential will always transfer power to the wheel with the LEAST amount of grip. Subaru's with a LSD in the rear will always transfer power to the wheel(s) with the most grip. However in the front, which has an open differential power will always be sent to the wheel with the least grip.
Also, in Subaru's with no limited slip differentials, power could only possibly be sent between the front and rear wheels with the least grip.
Someone please explain this to me since one of the reasons I'm leaning toward getting the WRX over the 2.5 RS is the LSD in the WRX. My Outback has the LSD and that car is unstopable in harsh weather conditions, so I'm afraid to get an AWD car without one.
Explanations Please. Thanks.
Anyway, I currently own an Outback and I'm thinking about purchasing a WRX.
I know my Outback has a limited slip rear differential, and also that the WRX has one but the 2.5RS does not.
So far so good. This is were I get confused. How does AWD transfer power "from the wheels that slip to the wheels that grip" if there is an open differential in the front, and in the case of the 2.5 RS and other Subarus which don't have a LSD in the rear?
An open differential will always transfer power to the wheel with the LEAST amount of grip. Subaru's with a LSD in the rear will always transfer power to the wheel(s) with the most grip. However in the front, which has an open differential power will always be sent to the wheel with the least grip.
Also, in Subaru's with no limited slip differentials, power could only possibly be sent between the front and rear wheels with the least grip.
Someone please explain this to me since one of the reasons I'm leaning toward getting the WRX over the 2.5 RS is the LSD in the WRX. My Outback has the LSD and that car is unstopable in harsh weather conditions, so I'm afraid to get an AWD car without one.
Explanations Please. Thanks.
01-07-2003, 04:02 PM
#2
Guest
Posts: n/a
Basically, an AWD car with open front and rear diffs will only transfer power between the front and rear. So if for instance you stopped with the right half of your car on a patch of ice, it would do you no good whatsoever. The open diffs would send all the torque to the wheels on the ice, and you would go nowhere. But in most real world situations it is still pretty nice.
01-07-2003, 04:11 PM
#3
Guest
Posts: n/a
So basically the LSD in the rear is worth it. I just read that the WRX STi will also have a LSD in the front, not to mention 300hp and ft/lbs of torque. Maybe I should just wait for an STi. That sounds like an amazing car.
Anyway back to my original post.
Is this statment true?: "Subaru cars with AWD and no limited slip differentials transfer power from the wheel (singular) with the least amount of grip in the front or rear to the wheel (singular) with the least amount of grip in the front or rear?"
I just signed on to this board and I will say this: "I love my Subaru Outback and I've owned one for 3 years now. It has performed flawlessly and if I could go back in time I would definitely buy it again." However, I really think that if you want the best traction possible then LSD's are the way to go, and I just don't think that Subaru's without the LSD in the rear are really AWD vehicles.
Anyway back to my original post.
Is this statment true?: "Subaru cars with AWD and no limited slip differentials transfer power from the wheel (singular) with the least amount of grip in the front or rear to the wheel (singular) with the least amount of grip in the front or rear?"
I just signed on to this board and I will say this: "I love my Subaru Outback and I've owned one for 3 years now. It has performed flawlessly and if I could go back in time I would definitely buy it again." However, I really think that if you want the best traction possible then LSD's are the way to go, and I just don't think that Subaru's without the LSD in the rear are really AWD vehicles.
01-08-2003, 03:26 AM
#4
no.
in a perfect world with completely flat roads, an open diff will send power to both sides.
if you lifted an awd vehicle and then start it and get in gear, you will see all 4 wheels going.
only when a difference in speed, will the differential start to work, ie. let the side with the LEAST amount of resistance have the power.
that's when any type of NON spool tractional adding differential will start to work.
in a viscous type diff, the gooey fluid will start to harden and will then "lock" up the other side.
other types of LSD work on clutch packs or even helical geared (like the detroit true-trac in my toyota truck).
so to answer your original question, the BEST traction adding type diff is a spool, which technicaly isnt a diff. it's just a device connecting the left and right axles in the diff housing...
next is the ARB air locker and the toyota eletronic locker design, when a mechanism will lock the two sides together, forming a spool. the nice thing about them is you can engage and disengage them on the fly. these 2 designs though, are essentially an OPEN diff, when unlocked.
now, a new type of user selectable locking diff combines an LSD with a locking action. i forget the company making this, and they have a llimited product application.
then, then is the detroit automatic locker. this better than a limited slip since when it is locked, it is a spool, but when, say you are making a turn, the dog-leg type gears will unlock and then relock. no user intervention is required.
then there is the LSD. LSDs dont offer 100% lockup like the ones mentioned above. maybe 50% to like 70% lockups, depending on the LSD design.
in a perfect world with completely flat roads, an open diff will send power to both sides.
if you lifted an awd vehicle and then start it and get in gear, you will see all 4 wheels going.
only when a difference in speed, will the differential start to work, ie. let the side with the LEAST amount of resistance have the power.
that's when any type of NON spool tractional adding differential will start to work.
in a viscous type diff, the gooey fluid will start to harden and will then "lock" up the other side.
other types of LSD work on clutch packs or even helical geared (like the detroit true-trac in my toyota truck).
so to answer your original question, the BEST traction adding type diff is a spool, which technicaly isnt a diff. it's just a device connecting the left and right axles in the diff housing...
next is the ARB air locker and the toyota eletronic locker design, when a mechanism will lock the two sides together, forming a spool. the nice thing about them is you can engage and disengage them on the fly. these 2 designs though, are essentially an OPEN diff, when unlocked.
now, a new type of user selectable locking diff combines an LSD with a locking action. i forget the company making this, and they have a llimited product application.
then, then is the detroit automatic locker. this better than a limited slip since when it is locked, it is a spool, but when, say you are making a turn, the dog-leg type gears will unlock and then relock. no user intervention is required.
then there is the LSD. LSDs dont offer 100% lockup like the ones mentioned above. maybe 50% to like 70% lockups, depending on the LSD design.
Last edited by ldivinag; 01-08-2003 at 03:29 AM.
01-08-2003, 08:18 AM
#5
it all depends on what you are trying to do.
front LSD is no good when you are road racing because it makes harder to turn in,
but it makes sense in gravel rallying because it gives traction on loose ground.
keep in mind the center diff is viscous LSD on any model (except the new STi)
the reason why STi has LSD in front is there. It needs LSD in front and rear because the center diff is open occasionally.
front LSD is no good when you are road racing because it makes harder to turn in,
but it makes sense in gravel rallying because it gives traction on loose ground.
keep in mind the center diff is viscous LSD on any model (except the new STi)
the reason why STi has LSD in front is there. It needs LSD in front and rear because the center diff is open occasionally.
Thread
Thread Starter
Forum
Replies
Last Post
DetailAddict
Teh Politics Forum
3
07-02-2008 03:12 PM
