Why are there so many AWD cars now?

[UG_Passat]

Ford Focus RS used the dual electronic Haldex setup as well. IMO those aren’t true AWD systems like we’ve been otherwise discussing, since if you burn up a Haldex there will be exactly 0% power going to that wheel regardless of conditions, at least how Ford explained it.

Haldex is an electronic slip and grip system, especially the older generations.. If the clutch can't lock up to any degree, then it can't transfer power. The newer generation take in a lot more data from sensors to "anticipate" slip and then tell the coupling to start locking up. Unfortunately, Haldex requires frequent fluid changes of its wet clutch, and requires additional maintenance of the pump, such as cleaning the pump screen of clutch particles.

In a viscous coupling, instead of an electronic controlled lock up clutch, the silicone fluid mechanical properties does the lockup within the clutch

 

[UG_Passat]

We agree on that part. But the part that’s still a fly in the ointment is that the viscous diff is always seeking to be at 50:50, even if it may momentarily allow a slightly different bias. It may allow some slip at one end, but it never tries to apply power in anything but a 50:50 differential. Same premise applies for turns, both side-to-side and front-to-back.

You can't take away power from one side and still call it a 50:50 condition, the laws of thermodynamics still applies to Subarus

Going back to default is aways the preferred operating condition. Subaru's electronic multiplate clutch will lock to 50:50, until it doesn't need to and will go back to 60:40 or 45:55, depending on the AWD system electronics.

a FWD-based system will always prefer to be in FWD mode, unless torque is needed in the rear.

Likewise in X-mode, the preferred operating condition is not having the ABS pump grabbing on a wheel(s) to keep moving forward, it will do that as needed to divert power across the axle, b

 

[edyvw]

Which means technically, you're not quite correct in your generalization of Torsen TBD use cases

I say, I am technically correct.
JFC.

 

[Ws6]

Best conventional awd is Acura SH AWD w/torque vectoring. That said, when its super nasty out, nothing can compete with my EV cars.

 

[OX1]

When you take away torque and give it to the other output shaft, it's no longer 50:50 at that time.

If the center differential was a true fixed 50:50, like a part time 4WD truck on 4-high, you have driveline bind when you turn the car on high traction surfaces, which is why you don't use 4-high on dry asphalt and concrete surfaces.

Agree, use 4 low on concrete "surfaces".

 

[CheezWhiz]

after getting stuck behind fwd vehicles on snow tires every year on spokane's south hill, i certainly wish that everyone here had either AWD or a true 4x4.

 

[IndyIan]

Best conventional awd is Acura SH AWD w/torque vectoring. That said, when its super nasty out, nothing can compete with my EV cars.

It would be interesting to compare say a 2200lb 1985 Tercel AWD wagon, vs a heavy EV with equal snow tires, in a variety of snow conditions. I think the Tercel would win braking, and handling, and maybe the first 10'-20' of acceleration in most, or at least some snow conditions. I don't think any 4500+lb AWD electric cars are going to be competitive ice racers, in the lower traction "street stud" or "rubber to ice" classes at least.
I find in slush, a heavy vehicle does do pretty well, unless its going way too fast and aquaplanes and lots of new vehicle come with quite wide tires, which isn't helping.
On hard packed snow or ice, then wider tires may help, but heavier weight of the vehicle isn't if you have to turn or stop.

For me atleast, I've found that super skinny snow tires on a light car works pretty well if you want to drive quickly in snow that its deep enough rub the bottom of the car. In stuff like this, with a skinny tire you can still maintain directional control while aquaplaning, and if go into a slide, the tires regrip quickly due to how light the car is.

 

[Ws6]

It would be interesting to compare say a 2200lb 1985 Tercel AWD wagon, vs a heavy EV with equal snow tires, in a variety of snow conditions. I think the Tercel would win braking, and handling, and maybe the first 10'-20' of acceleration in most, or at least some snow conditions. I don't think any 4500+lb AWD electric cars are going to be competitive ice racers, in the lower traction "street stud" or "rubber to ice" classes at least.
I find in slush, a heavy vehicle does do pretty well, unless its going way too fast and aquaplanes and lots of new vehicle come with quite wide tires, which isn't helping.
On hard packed snow or ice, then wider tires may help, but heavier weight of the vehicle isn't if you have to turn or stop.

For me atleast, I've found that super skinny snow tires on a light car works pretty well if you want to drive quickly in snow that its deep enough rub the bottom of the car. In stuff like this, with a skinny tire you can still maintain directional control while aquaplaning, and if go into a slide, the tires regrip quickly due to how light the car is.
View attachment 184847

That actually looks very driveable. What I drove looked clear. It was about 1/4" of ice only.

 

[dlundblad]

Brakes and physics pretty much work the same with or without AWD.

One would definitely think that. There’s a video out there of 2 Cherokee XJ’s driving on snowy terrain. One was in 4WD while the other wasn’t… the 4WD did better in every aspect.

 

[atikovi]

One would definitely think that. There’s a video out there of 2 Cherokee XJ’s driving on snowy terrain. One was in 4WD while the other wasn’t… the 4WD did better in every aspect.

Driving yes. Braking, not so much difference.

 

[dlundblad]

Driving yes. Braking, not so much difference.

Driving and braking both.