Thread: ('11+) explain imprezas AWD?
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Old 12-24-2012, 11:06 AM   #14
Snow Drift
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Member#: 75071
Join Date: Nov 2004
Chapter/Region: Tri-State
Location: NYC
Vehicle:
4 Train - Subway
Past: 05, 08, 11 Red WRXs

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Quote:
Originally Posted by motorace View Post
from what i know about 4x4 ford trucks, which i can be wrong about, the 2 fronts wheels would be locked together with one of the rear tires, with least resistance rear, having power. thus, 3 wheels have power while in 4x4.



what does an impreza have? with the computer transferring power to slipping wheels, does that means it's similar, as in 3 wheels have power?

(or like other brand awd vehicles, where its just 1 wheel up front and 1 wheel in the back and call it awd?)
No, all Subarus (save the BRZ and foreign kei cars) use full-time awd which is never deactivated. All 4 wheels receive power all the time unless slipping occurs where the system needs to reroute it.

2011+ Impreza 5MT

Rear Differential = Open (VDC applies brake to slow spinning wheel)
Front Differential = Open (VDC applies brake to slow spinning wheel)
Center Differential = 50/50 torque split ALL the time. A viscous coupling center differential has metal plates that are connected to either the front or rear driveshafts and are surrounded by a viscous fluid. During normal driving the metal plates spin at an even 50/50 rate. Upon either axle slipping that shaft's metal plates will begin to spin at a faster rate that the other. The shearing action of the plates and heat from friction causes the fluid to harden. The hardening fluid thus slows the spinning plate and forces all plates to spin at 50/50 again. This is a VERY good system.
Turn off VDC when in deep snow to prevent Engine Power Reduction from stalling the motor.

2011+ Impreza CVT

Rear Differential = Open (VDC applies brake to slow spinning wheel)
Front Differential = Open (VDC applies brake to slow spinning wheel)
Center Differential = Actively changing torque split (60/40 normally per SOJ and SCI). A multiplate clutch system is housed in the center differential which can be compressed based on a number of sensors (throttle position, wheel slip, steering, etc). The computer will determine how much clamping pressure to apply to the center, thus altering the amount of torque flowing between the front and rear driveshaft. A major difference between Subaru and others is that the system is not FWD until slip. The system will alter the torque split if you merely push down the gas pedal. It is not a fwd car that only kicks in the rear tires in bad situations. This system works well for normal snow driving. Not designed for off-road.
Turn off VDC when in deep snow to prevent Engine Power Reduction from stalling the motor.
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Last edited by Snow Drift; 12-24-2012 at 11:12 AM.
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