Ford AWD vs Subaru "Active AWD"

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supasixfo
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Ford AWD vs Subaru "Active AWD"

Post by supasixfo »

Realized this was more of powertrain question than engine one...

So what i was hoping would be a very simple analysis has turned into a much more complicated one. the other car my friend is considering is a ford fusion awd. I wanted to say one was clearly superior to the other, but it appears like both systems are more similar than they are different.

Everything i have read about ford's system points to a "haldex-like" system. what i have read about the forester XT is also haldex-like.

"The vehicle is equipped with a four wheel drive (4WD) system, also referred to as intelligent torque control coupling (ITCC) , that is always active and requires no driver input...The system continuously monitors vehicle conditions and automatically adjusts the torque distribution between the front and rear wheels. During normal operation, most of the torque is sent to the front wheels. If wheel slip between the front and rear wheels is detected, or if the vehicle is under heavy acceleration (high throttle position), the AWD system increases torque to the rear wheels to prevent or control wheel slip.

The system consists of a power transfer unit (PTU), 4WD control module, rear axle and a solenoid actuated intelligent torque coupling control device. The module varies the torque sent to the rear wheels by sending a duty cycle based on the amount of current sent to the clutch to the active torque coupling device located inside the rear axle. "
(http://www.fordfusionforum.com/index.ph ... drive-awd/)

Similarly for the subaru forester xt:
"The mechanism that transfers torque fore and aft is contained within the transmission’s tailshaft. To the casual observer it looks just like a typical hydraulic clutch found in any automatic. The key difference in this clutch pack is its operation. It’s designed to slip according to how much all-wheel drive is needed... the multi-plate transfer (MPT) clutch uses a special friction material that easily withstands the friction loads generated during torque transfer. (Also referred to as VTC = Variable Transfer Clutch)
The MPT’s operation is controlled by the Transmission Control Unit (or TCU) and constantly changes dependent on how the vehicle is being driven. To get more all-wheel drive, the TCU increases the hydraulic pressure to the clutch for less slippage. Less all-wheel drive calls for more slip and the TCU reduces the hydraulic pressure to the clutch.
Under normal, dry pavement operation torque split is about 90% front and 10% rear. This distribution helps to compensate for the car’s weight distribution and resultant smaller effective rolling diameter of the front tires. As weight transfers to the rear of the vehicle, (i.e., under acceleration), the TCU shifts the torque split more toward the rear wheels."
(http://legacygt.com/forums/showthread.p ... 5d&t=48112)

The only thing i was really able to deduce was that the ford has open front and rear "active coupling unit" (viscous?). Not sure what's in the forester xt. supposively there is an open front and rear lsd, but what is it? clutch-pack? torsen? viscous?

[*]http://www.subaruforester.org/vbulletin ... ost19.html
[*]http://www.awdwiki.com/haldex.html#4
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thermobox
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Re: Ford AWD vs Subaru "Active AWD"

Post by thermobox »

Viscous in Manual Trans for 'Continous AWD'. Clutch Pack in Auto Trans for 'Active AWD'.
Automatic transmission uses 'Active all wheel drive', with electronically controlled variable transer clutch that detects wheel spin and directs power to the front or rear axle as needed. Normally 80/20 (or 90/10 depending on source) front rear power split.
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