AWD with open diffs

[rumatt]

Fun experiment.

https://youtu.be/FOmZIu_y1js

Though as the first comment conveys quite nicely, they could have mentioned open diffs.

[Jeff_DML]

I thought most Subaru's just have a center lsd and open front and rear diffs. Just the STI has all the fancy diffs. My 2004 wrx had a rear lsd but pretty sure the new ones have open.

[bren]

I'm not aware of any "pedestrian" vehicle with individual limited-slip diffs.

What was the point of constant throttle in that test? Other than to show that Subi may send more power to the rear by default. If you are stuck, are you really worried about conserving fuel?

My guess is most of those systems can only transfer a small percentage of the power rearward which was exacerbated by only providing limited throttle - that and/or their traction control systems were switched on.

[rumatt]

I thought most Subaru's just have a center lsd and open front and rear diffs. Just the STI has all the fancy diffs. My 2004 wrx had a rear lsd but pretty sure the new ones have open.
That was my understanding as well. I guess this car had some sort of ediff system in the rear diff?

[rumatt]

I'm not aware of any "pedestrian" vehicle with individual limited-slip diffs.

What was the point of constant throttle in that test?

No but I'd think this is the ideal scenario for an ediff. Who cares if it gets you around a race track as fast as possible. But if you end up with 3 of 4 wheels on ice? I'd think it should be able to help you get unstuck.

I think the constant throttle was just to point out that the car bucking and sliding backward wasn't due to the driver messing with the throttle.

[JST]

A test like this is (obviously) designed to highlight one particular failure mode which the Subaru can handle but the others can't. Useful if you have a roller ramp setup in your driveway, but otherwise I'm not sure of the utility.

For what it's worth, I think I've said before that the Haldex setup in the Golf R has never given us even the slightest bit of trouble in real-world conditions. The car can unstick itself from some pretty hairy snow/ice combos. Is there a particular set of circumstances where a 50:50 system might work better? I guess, but I've never encountered it.


EDIT: It's not the primary function, but I would guess that the electronic trickery that lets the Focus RS do "drift mode" would be useful in a circumstance like this, too.

[bren]

No but I'd think this is the ideal scenario for an ediff.
When are you ever going to get stuck and think: "well, self, I can only use 20% throttle here - sure sucks that my rear diff only sees 5%, but oh well."

No, you apply 100% throttle so that the rear sees 60% and has enough power available to actually move the 4k pound vehicle mass.

[rumatt]

No, you apply 100% throttle so that the rear sees 60% and has enough power available to actually move the 4k pound vehicle mass.

If that's true, sure I agree. But if you have an open diff back there more throttle isn't going to help you. The left rear wheel on those cars was receiving power and was spinning like mad. It just wasn't transferring to the right.

[rumatt]

A test like this is (obviously) designed to highlight one particular failure mode which the Subaru can handle but the others can't. Useful if you have a roller ramp setup in your driveway, but otherwise I'm not sure of the utility.

I'm a computer scientist. This is like a test case for an extreme condition. It's fun. :mad2:

But I don't think it's too insane of a scenario. 3 wheels on ice, one on dry. Is that so ridiculous to ask that your AWD vehicle is not rendered useless in that condition? :dunno:

[bren]

I'm a computer scientist. This is like a test case for an extreme condition. It's fun. :mad2:

But I don't think it's too insane of a scenario. 3 wheels on ice, one on dry. Is that so ridiculous to ask that your AWD vehicle is not rendered useless in that condition? :dunno:

You saw that video a couple winters ago of the guy with the Grand Cherokee right? :lol:

edit:

this one (turn down the volume)

CuTXUcoGdhw

[Josh (PA)]

A good set of snow tires (like Nokians) fixes a lot of these problems.

[rumatt]

You saw that video a couple winters ago of the guy with the Grand Cherokee right? :lol:


:lol: :lol:

He just needed to slam the doors harder. :bustingup

In his case it seems the AWD did OK. The left side wheels were spinning nicely. I'm guessing the wheels on the other side had equal or less traction and were spinning as well. If so, you can't ask for much more from the Jeep

[wdc330i]

You saw that video a couple winters ago of the guy with the Grand Cherokee right? :lol:

edit:

this one (turn down the volume)

CuTXUcoGdhw

That's why I always kept one of these in the X5--even with AWD and snow tires.

[Jeff_DML]

I would be kind of pissed that my trail rated jeep got stuck like that:D I am guessing the fancy offroad version has the locking diffs option?