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Old 13 Oct 2009, 08:35 PM   #1 (permalink)
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subaru AWD

I now there are many different aplication when making AWD car. First big difference is weather car has all time or part time AWD, second is wether it has torsen, visco or multipleclutch as center LSD, and third if it is electronicaly or mechanicaly controlled.

But I can't find how does Impreza (WRX) or Lancer (EVO) ADW works.
If I am not mistaken Impreza uses visco center diff and torsen at rear and front and Lancer uses clutch type center diff and torsen.

But as I know differential has one input shaft and two outputs in contrast to visco coupling and haldex that only has input and output. So how can Subaru's or Mitsubishis's center diff split torque between front and rear?
Any schematics would be appriciated.

this is what I found for evo but don't know how it works and weather it is center or rear diff.

Last edited by bogicevic; 13 Oct 2009 at 08:41 PM.
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Old 14 Oct 2009, 07:35 AM   #2 (permalink)
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Subaru AWD

All i have is this info:

Viscous: Used as the center and rear differentials in the WRX/RS (08+ WRX has an open rear diff). Varies power applied between two axles via fluid dynamics and discs. This type of unit is filled with a silicone based fluid that becomes thicker as the difference in input shaft and output shaft speed increases, thereby increasing the viscosity of the fluid and the grip between the input and output discs, which do not actually touch each other.

Suretrac: Only available on the 2004 STi. Manufactured by AP Racing, this unit comes stock in the front differential of the 2004 STi. It is a mechanical type differential that employs a set of specially shaped teeth to intelligently transfer power, unlike the bevel gears that are used in conventional LSDs. Very similar in operation to the torsen type, though through different mechanical means.

Open differential: Used as the front differential in the WRX/RS. In a nutshell, itís one wheel drive. The wheel with the least amount of traction will have majority (if not all) of the vehicleís power applied to it.

DCCD: Short for Driver Controlled Center Differential. Used on the STi. Planetary center differential in conjunction with an electronically managed continuously variable transfer clutch. And as the name suggests, it allows the driver to control the torque bias of the center diff by a turn of the thumbwheel.

Torsen type differential: Used as the front (2005+) and rear differentials in the STi. Short for TORque SENsing differential. Itís worth mentioning that though Torsen is a brand name, it is the most commonly used name for this type of differential. This type of unit is also known as a helical or mechanical type. It uses gears to split power between two axles. Once one wheel is off the ground or slips, it in essence, becomes an open diff or exhibits limited traction based on the torque bias of the unit. It has the added drawback of weight. The additional torque required to rotate a heavier differential will require more energy, energy is heat, heat is friction, friction and heat are wasted energy. It requires more energy to drive and this can be shown on a chassis dynamometer if same car is measured before and after the differential change. The other downside is that if the engine is quite powerful and extra special abuse is administered (high grip launches, donuts, etc.) they will explode. These broken gears will make their way through the case and can cause considerable damage. Keep this in perspective though, as very few cars exert this kind of power and those owners tend to understand what that power is capable of breaking.

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Old 14 Oct 2009, 04:27 PM   #3 (permalink)
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Re: subaru AWD

This isn't really any answer
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