Why are there so many AWD cars now?

[SubieRubyRoo]

Manuals with the viscous coupling are not fixed 50:50. The default split is 50:50, and the coupling can go up to around 70:30 or 30:70 depending on which axle has slip.

That’s nowhere in Subaru’s literature nor in the body of evidence in 20+ years of manual Subarus that I’ve seen. The STi has an adjustable center, and I believe can only be set to 35:65 to 50:50. The Forester, Impreza, Legacy/Outback manuals from what I’ve read and what Fenske’s had are “locked” at 50:50; the front diff is open so the spinning tire gets the power, and only the Legacy/Outback with LSD are any better in the rear.

If you’ve got definitive proof that it’s not 50/50 I’d like to see it, because the locked split was always what was of interest to me.

 

[UG_Passat]

That’s nowhere in Subaru’s literature nor in the body of evidence in 20+ years of manual Subarus that I’ve seen. The STi has an adjustable center, and I believe can only be set to 35:65 to 50:50. The Forester, Impreza, Legacy/Outback manuals from what I’ve read and what Fenske’s had are “locked” at 50:50; the front diff is open so the spinning tire gets the power, and only the Legacy/Outback with LSD are any better in the rear.

If you’ve got definitive proof that it’s not 50/50 I’d like to see it, because the locked split was always what was of interest to me.

Sounds like both you and Jason Fenske doesn't know how a viscous coupling works.

What do you think the LSD is on the older upper trim Legacy/Outback/Forester has? It has a viscous coupling, that transfer power from the rear wheel that slips to the rear wheel that grips.

And early Toyota highlander had a fixed 50:50 AWD system.

 

[edyvw]

The only AWD system I'm familiar with is Subaru. I've seen some CRV's get out of some snow that they were struggling in but those systems are not the greatest and are too reactionary. Subaru's 60/40 torque split keeps traction going. Of course tires are always the biggest factor. Subarus are little tanks with snow tires.

People are always going to be idiots and you see this when they drive their first 4wd or AWD car in a snowstorm. They are way too overconfident and end up in a ditch anyway.

Subarus are one of the few AWD vehicles that can drive on the beach successfully. Most of the others get stuck.

Maybe the other manufactures just jumped on the bandwagon due to Subaru?

The only vehicle more common in the ditch in Colorado, besides tourists renting 6,000lbs SUV, is your average Subaru.

 

[buster]

The only vehicle more common in the ditch in Colorado, besides tourists renting 6,000lbs SUV, is your average Subaru.

Overconfident, inadequate tires and poor judgment. No AWD or 4wd system can compensate for that.

 

[SubieRubyRoo]

Sounds like both you and Jason Fenske doesn't know how a viscous coupling works.

What do you think the LSD is on the older upper trim Legacy/Outback/Forester has? It has a viscous coupling, that transfer power from the rear wheel that slips to the rear wheel that grips.

And early Toyota highlander had a fixed 50:50 AWD system.

That’s funny that you think we’re the ones that don’t know how a viscous coupling works. As one side spins faster than the other, the viscous coupling fights the speed change because it is only truly happy when both outputs are at the same speed (and you acknowledge this in your anecdote); in this case it is the overall front axle speed and rear axle speed. If the viscous coupling is only truly “happy” when both outputs are at the same speed, meaning EQUAL, what power split does that sound like you? Sure sounds like 50:50 to me, and to everyone else who grasps a viscous coupling. Just because traction itself may only be present in a 90:10 relationship, doesn’t impact the fact that a viscous coupling is always working to apply a 50:50 split. In effect, the sole reason for the viscous coupling is to use any slip that is present on one wheel or axle to match the speed on the other wheel or axle.

By definition, then, if the front axle loses traction and is spinning faster than the rear, the viscous center differential will “suck” power away from a maybe 90 (spinning) :10 (not spinning) split and send more power to the rear… ALWAYS in pursuit of maintaining zero slip between both outputs, hence 50:50. The viscous coupling itself can never seek anything else when both outputs are coupled to the same output gear ratio.

 

[SubieRubyRoo]

Overconfident, inadequate tires and poor judgment. No AWD or 4wd system can compensate for that.

Not even Subaru AWD can fix stupid.

 

[edyvw]

Not even Subaru AWD can fix stupid.

Which is OK system. Far from being the best.

 

[SubieRubyRoo]

Which is OK system. Far from being the best.

Personally, I think the CVT versions are a step back from some of their past technologies; they also missed some opportunities because of cost avoidance over the years. But for the average Jane Doe, the Subaru system is arguably among the most advanced “100% hands off” system available, certainly for the money.

Which ones do you feel are more advanced?

 

[PF52]

My AWD Subaru stays in the garage all winter. I own beaters for driving in the snow!

 

[edyvw]

Personally, I think the CVT versions are a step back from some of their past technologies; they also missed some opportunities because of cost avoidance over the years. But for the average Jane Doe, the Subaru system is arguably among the most advanced “100% hands off” system available, certainly for the money.

Which ones do you feel are more advanced?

Audi, BMW, MB, Land Rover, others utilizing Torsen's etc.
I mean OK, in that class, maybe their system might have better performance in certain situations, but both Honda and Toyota have vectoring rear axle, VW has it in some models (front). For the average Jane Doe, any system today is good, even that hybrid in Toyota with an independent rear axle. Slap good tires; they are all good for vehicles that are intended to drop kids to school. Those vehicles usually have more serious shortcomings than the simplicity of AWD.

 

[SubieRubyRoo]

Audi, BMW, MB, Land Rover, others utilizing Torsen's etc.
I mean OK, in that class, maybe their system might have better performance in certain situations, but both Honda and Toyota have vectoring rear axle, VW has it in some models (front). For the average Jane Doe, any system today is good, even that hybrid in Toyota with an independent rear axle. Slap good tires; they are all good for vehicles that are intended to drop kids to school. Those vehicles usually have more serious shortcomings than the simplicity of AWD.

I agree Torsen would be an upgrade (and that’s what I alluded to in their missed opportunities) but in the sub-20 to $27ish K range I don’t believe there’s anything better; maybe a few peers but not many. Quaife would be another option… but in terms of simplicity and results, the system is difficult to beat on a cost-performance ratio.

Yes, Land Rover is among the absolute cream of the crop, but what’s the cheapest LR with the full kit run? You could likely own 3 decently outfitted Subarii for the cost of one base LR

 

[UG_Passat]

That’s funny that you think we’re the ones that don’t know how a viscous coupling works. As one side spins faster than the other, the viscous coupling fights the speed change because it is only truly happy when both outputs are at the same speed (and you acknowledge this in your anecdote); in this case it is the overall front axle speed and rear axle speed. If the viscous coupling is only truly “happy” when both outputs are at the same speed, meaning EQUAL, what power split does that sound like you? Sure sounds like 50:50 to me, and to everyone else who grasps a viscous coupling. Just because traction itself may only be present in a 90:10 relationship, doesn’t impact the fact that a viscous coupling is always working to apply a 50:50 split. In effect, the sole reason for the viscous coupling is to use any slip that is present on one wheel or axle to match the speed on the other wheel or axle.

By definition, then, if the front axle loses traction and is spinning faster than the rear, the viscous center differential will “suck” power away from a maybe 90 (spinning) :10 (not spinning) split and send more power to the rear… ALWAYS in pursuit of maintaining zero slip between both outputs, hence 50:50. The viscous coupling itself can never seek anything else when both outputs are coupled to the same output gear ratio.

When you "suck" away power via the fluid thickening at the multiplate clutch, the non-slipping side gets a portion of torque/power, so at that moment, it's no longer at 50:50 split. One side will momentarily have more power/torque than the other side (the non-spinning side will be heating up the silicon fluid to thicken it, to essentially "lock" that side of the clutch, to transfer torque), to the side that grips will have more than 50% bias

That's the part you're excluding.

Then as the output shafts get back to equilibrium, it goes back to 50:50, when it's "happy"

 

[SubieRubyRoo]

When you "suck" away power via the fluid thickening at the multiplate clutch, the non-slipping side gets a portion of torque/power, so at that moment, it's no longer at 50:50 split. One side will momentarily have more power/torque than the other side (the non-spinning side will be heating up the silicon fluid to thicken it, to essentially "lock" that side of the clutch, to transfer torque), to the side that grips will have more than 50% bias

That's the part you're excluding.

Then as the output shafts get back to equilibrium, it goes back to 50:50, when it's "happy"

Exactly… a viscous is designed for equilibrium, 50:50. It never “adds” past 50% power to a given axle. It will never spin the axle with traction faster than the axle without traction. This means a “temporary” spin does not change the bias of the viscous coupling itself. It’s as close to a 1:1 power transfer to both axles as you can have without having a mechanical coupling, which prevents the “hopping” in corners or other situations where one axle spins faster than the other.

 

[edyvw]

I agree Torsen would be an upgrade (and that’s what I alluded to in their missed opportunities) but in the sub-20 to $27ish K range I don’t believe there’s anything better; maybe a few peers but not many. Quaife would be another option… but in terms of simplicity and results, the system is difficult to beat on a cost-performance ratio.

Yes, Land Rover is among the absolute cream of the crop, but what’s the cheapest LR with the full kit run? You could likely own 3 decently outfitted Subarii for the cost of one base LR

I agree, getting some base Impreza with that AWD is not possible in that price range among competitors.

 

[UG_Passat]

Audi, BMW, MB, Land Rover, others utilizing Torsen's etc.
I mean OK, in that class, maybe their system might have better performance in certain situations, but both Honda and Toyota have vectoring rear axle, VW has it in some models (front). For the average Jane Doe, any system today is good, even that hybrid in Toyota with an independent rear axle. Slap good tires; they are all good for vehicles that are intended to drop kids to school. Those vehicles usually have more serious shortcomings than the simplicity of AWD.

BMW xdrive uses an electronic multiplate clutch.

Porsche when adapting the Q5 to Porsche Macan, deemed the Torsen differential to be too slow in reaction, so, the Macan gets their electronically controlled multiplate clutch.

Audi used to use Torsen C differentials, until around 2010, started to roll in the Crown gear differential, which is more of a mechanical multiplate clutch design. And for the "fuel efficient" Quattro to replace Torsen, the Magna "Quattro with Ultra technology" uses a electronically controlled multiplate clutch system

The MK8 Golf R's Haldex system also gets 2 clutches in the rear axle, similar to Honda/Acura and Toyota.

 

[edyvw]

BMW xdrive uses an electronic multiplate clutch.

Porsche when adapting the Q5 to Porsche Macan, deemed the Torsen differential to be too slow in reaction, so, the Macan gets their electronically controlled multiplate clutch.

Audi used to use Torsen C differentials, until around 2010, started to roll in the Crown gear differential, which is more of a mechanical multiplate clutch design. And for the "fuel efficient" Quattro to replace Torsen, the Magna "Quattro with Ultra technology" uses a electronically controlled multiplate clutch system

The MK8 Golf R's Haldex system also gets 2 clutches in the rear axle, similar to Honda/Acura and Toyota.

Yeah, and?

 

[UG_Passat]

Exactly… a viscous is designed for equilibrium, 50:50. It never “adds” past 50% power to a given axle. It will never spin the axle with traction faster than the axle without traction. This means a “temporary” spin does not change the bias of the viscous coupling itself. It’s as close to a 1:1 power transfer to both axles as you can have without having a mechanical coupling, which prevents the “hopping” in corners or other situations where one axle spins faster than the other.

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.

 

[SubieRubyRoo]

BMW xdrive uses an electronic multiplate clutch.

Porsche when adapting the Q5 to Porsche Macan, deemed the Torsen differential to be too slow in reaction, so, the Macan gets their electronically controlled multiplate clutch.

Audi used to use Torsen C differentials, until around 2010, started to roll in the Crown gear differential, which is more of a mechanical multiplate clutch design. And for the "fuel efficient" Quattro to replace Torsen, the Magna "Quattro with Ultra technology" uses a electronically controlled multiplate clutch system

The MK8 Golf R's Haldex system also gets 2 clutches in the rear axle, similar to Honda/Acura and Toyota.

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.

 

[UG_Passat]

Yeah, and?

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

 

[SubieRubyRoo]

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.

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.