[JWA]

Originally Posted by CGMDan

Those of us that have been around here for a while, have read more than a few tech articles about the system. Not "media" articles but discussions on actual Subaru tech manuals. Some of which he's posted above.

Ok, cool. Are any of these "tech articles" available to the common customer/public?

What I find hard to believe is that these tech articles you refer to explain that the system operates in a completely different manner than explained in the various sources I have access to. I find it hard to believe from both a practical standpoint and because all of my experience in both my '07 STI and my '08 STI have indicated that the system works as explained by these sources and that Rootus's assertions to the contrary are incorrect.

Nobody is saying that the system uses some wild variable gearing system, but that the DCCD system's solenoid LSD is able to adjust the nominal torque transfer by adjusting the locking action of the mechanical dif, and that it can do this "on demand". Rootus says this is BS.

Could you please point me to the appropriate sections in the "actual Subaru tech manuals" where it is explained that the DCCD system is not capable of varying the torque transfer on demand (again, by the solenoid LSD adjusting the locking factor) as Rootus has stated? I will go to my local dealer tomorrow to read them.

[Rootus]

Originally Posted by JWA

Ok, cool. Are any of these "tech articles" available to the common customer/public?

Subaru makes the shop manual available to the public for a very small fee.

Could you please point me to the appropriate sections in the "actual Subaru tech manuals" where it is explained that the DCCD system is not capable of varying the torque transfer on demand (again, by the solenoid LSD adjusting the locking factor) as Rootus has stated? I will go to my local dealer tomorrow to read them.

Did you read the sections that I posted above? You can go download the manual yourself from Subaru and read the same stuff for each of the model years.

Please don't take this the wrong way, but ... I'm not going to try any harder to convince you. This topic has been hashed out so many times, in so many places, and I only really enjoyed feeling the pain when I was working to understand it myself . The information is out there, I encourage you to research it and learn how the system works. I'd recommend you avoid marketing materials, since those are some of the least factually correct sources (and just because it's the advertising agency Subaru uses doesn't make them any better ).

[JWA]

Originally Posted by Rootus

Did you read the sections that I posted above?

I did, and the explanation in the shop manual sections that you have on your site seem to directly contradict your statements in this thread. That's why I don't understand where you're coming from.

Originally Posted by Rootus

Please don't take this the wrong way, but ... I'm not going to try any harder to convince you.

No problem, and understood. Take care.

[lackskill]

Originally Posted by JWA

Then what would a 50/50 split mean to you? 100% of the torque is transferred through the system, with half of it powering each side, right?

With the differential locked, it no longer acts as a differential. It effectively becomes the equivalent of a transfer case or a spool (for the sake of this discussion anyway). Neither of those can redistribute power since they are a direct drive. 100% of the torque available goes front and rear OR to the wheel with the most mechanical grip, in which case the other wheels are receiving no torque (for the basis of this argument the amount of torque to simply spin the wheel is 0, and unpredictable dynamics such as chassis flex are not factored). I can see where the 50/50 argument comes from, and it is fed by advertising jargon. In any event, the differential is not causing the shift in torque distribution, it's simply allowing (or not allowing in the case of full lock) torque to be distributed by using varying degrees of lockup.

[Subw00er]

Ok, two easy questions to balance all the brain-bleeding ones..

1. If I want the car to act most like a RWD car (read: oversteer), do I go to manual mode, and select the first bar (the smallest one, farthest from LOCK)?

2. On the AUTO setting, would the "Auto-" make the car act more like a RWD car?

To be honest, I cant tell any difference between any of the settings (except LOCK of course). Is the real world application for DCCD only when stuck in mud or something? I was hoping the DCCD would let me take liberties with the rear end and then tune it back to 50/50 for daily driving. I'm a powersliding master with RWD cars, but I cant figure out how to do on this thing. It feels a little like big brother... maka it stop!!

[TarmacST1]

I tried that last night. with tc off first i tried it on auto. On auto setting i went about 45-50 on 3rd gear, down shift to 2nd and chucked the wheel and floored it. it was pretty stable out the corner. In manual mode i tried the samething and the backend wobbled a little more than before.

[stretch]

I'm so glad there are people here that understand the AWD system well enough to refute the dribble that magazines say. The magazines either try to overly dumb down the explanations or don't understand how the AWD works. There is no variable torque bias, as others have now said.

Full open will feel the most RWD because of the vehicle's weight distribution and torque split. The car sends more torque to the rear wheels, and those wheels have less weight on them (until weight transfers rearward under throttle). Thus, the rear wheels will have a tendency to break away first unless you're smooth with the throttle.

With an open center differential, which you never fully have on a 2006+ STI, the car will send more torque to the tires with the least grip. So with an open differential, you only need to get a set of tires to begin slipping and they will keep spinning forever until you back off on the throttle. Anyone who has driven a front wheel drive family sedan in snow should be familiar with this phenomenon. (This is when the LSD kicks in, to prevent endless wheel spin.)

With no center differential (fully locked), the car will always send torque proportionately to the tires with the most grip. All your tires will lose grip simultaneously when pushed too hard. You may still get oversteer depending on your suspension setup, but this is not a tendency that was caused by torque distribution.

It is impossible to force your center diff to fully open, though- a mechanical LSD engages with a relatively soft clutch, even with the computer-controlled clutch disabled. 2004 and 2005 STI's lacked this second mechanical LSD, instead relying on a computer, and could become stay 100% open. They also had a higher rear torque bias. Thus, these cars felt much, much more RWD.

I don't think the 2006+ AWD system every feels very RWD, but I don't have nearly as much seat time behind one either. Still, the same rules apply, even if to a lesser degree.

[Subw00er]

So stretch, is the most open setting the one with the single bar (smallest bar away from LOCK) on manual setting?

[kris]

Originally Posted by Subw00er

So stretch, is the most open setting the one with the single bar (smallest bar away from LOCK) on manual setting?

That's correct, one small bar is the most open setting

[supermarkus]

It damned near takes heroics to get the same kind of drift angles in an AWD car as you can with a RWD car. The levels of grip available make these cars relatively poor drifters unless you're on gravel or something. Don't get your hopes too high for dorifto.

[lackskill]

Originally Posted by stretch

I'm so glad there are people here that understand the AWD system well enough to refute the dribble that magazines say. The magazines either try to overly dumb down the explanations or don't understand how the AWD works. There is no variable torque bias, as others have now said.

I would just like to add, that under VERY few circumstances, should you EVER listen to technical data from an advertisement funded source. Advertisers want you to not be able to understand the product. That way they can over-glorify it, completely lie about it, and make you feel like you can't live without it. All the while it was really nothing special.

Referring only to the proverbial "it", of course. The Subaru AWD system really is a thing of beauty, but also one of the most complex systems. Mazda and VW also have fairly complex AWD systems. But only because they were just taking a FWD platform and adding torque to the rear wheels, which takes a level of technical complexity to save money and time.