[hwy61]

Hello All, I've read the manual, I've searched, I've experimented but I haven't been able to figure out how, when, where and why you use different settings on the DCCD.

auto-------------the computer monitors wheelspin and controls??????
lock-------------when, where, why, under what conditions is this used?????
rear bias--------ok, 65% of power to the rear wheels????? good for????launching with a little wheel spin, sliding around curves??
those settings in-between-----the diff. really drags here if driving in a slow circle on asphalt, the inner rear wheel almost skids from some friction somewhere in the drive-line. The DCCD will make a really terrible knocking sound in some positions and the manual says don't worry, it's normal.

Under what driving conditions would you use the various DCCD options. A really fancy device that the manual does almost no explaining on. Hwy61 Oh yeah, I'll be running around the Barber Track in December, what setting for that?

[Nachos Libres]

This topic has been covered many times, and basically the Subaru Technician's Guide (or whatever it's called) says the settings are Auto ; 100% ; 85% ; 65% ; 35% ; 15% ; 0%. That's going from top down. These settings change the amount of lockup placed on the center differential, which can affect torque distribution but it's not like you can say, "hmmm, I'm going to use this other setting to change the torque from 35f/65r to 50f/50r." I think the DCCD was designed more for an advanced traction control device, instead of a manual torque distribution device.

Explanations of DCCD
DCCD Operations and Controls
DCCD Primer
DCCD Questions
More DCCD Discussion
Even More DCCD Discussion

[wdb]

First off, let's be clear as to what the DCCD is. DCCD stands for "Driver Controlled Center Differential". It's a fancy way of saying that Subaru took their already existing, electronically controlled, fully automatic center differential, and added a switch and a control wheel in the center console so that the driver could override the control unit.

This next part is important. All the DCCD does, no matter what mode it is in, is adjust the amount of lockup between the front and rear output shafts of the center differential. It doesn't perform magic; it doesn't change the car from FWD to AWD to RWD, it doesn't send all the power to the front or rear wheels, and it doesn't change the torque distribution. In '04 and '05 STi's the torque distribution is 35F/65R, and the center differential is an open design. In '06 they went to a limited slip center differential and changed the torque distribution to 41F/59R.

Originally Posted by hwy61

auto-------------the computer monitors wheelspin and controls??????

The computer monitors a whole slew of stuff, not just wheelspin. Since you read the stuff available here you already know that.

lock-------------when, where, why, under what conditions is this used?????

Use it on dirt, gravel, snow, ice, and other very, very, slippery surfaces.

rear bias--------ok, 65% of power to the rear wheels????? good for????launching with a little wheel spin, sliding around curves??

That's not what it does. See above.

Oh yeah, I'll be running around the Barber Track in December, what setting for that?

From what I've read, if you want the fastest lap times leave it in Automatic. If you want the car to feel a certain way -- at the expense of lap times -- adjust it manually.

[Davenow]

Originally Posted by wdb

This next part is important. All the DCCD does, no matter what mode it is in, is adjust the amount of lockup between the front and rear output shafts of the center differential. It doesn't perform magic; it doesn't change the car from FWD to AWD to RWD, it doesn't send all the power to the front or rear wheels, .

Dont bother wasting your breath. I tried to explain this to a bunch of these numbskulls and just got flamed and called an idiot. Some people are just to stupid to be helped, which is why I have stopped helping people here. Not everyone here is that way, but I am sick of getting kicked in the nuts for trying to help people out. A few ruined it for everyone.

The funny part is you know they wont have the balls to flame you or call you an idiot, becuase they know you will beat them with a ban stick

[wdb]

Originally Posted by Davenow

Dont bother wasting your breath. I tried to explain this to a bunch of these numbskulls and just got flamed and called an idiot.

Patience, patience. Sometimes the road to enlightenment must be traveled over and over and over again.

Seriously though, let's face it: for most people, differentials are complicated gizmos that do some kind of mumbo jumbo stuff and then the wheels turn. With a car like the the STi, where such a device is even more complex, plus it is highlighted in the marketing strategy, and the driver is given manual control, well... let's just say that a lot of confusion and questions are to be expected.

The funny part is you know they wont have the balls to flame you or call you an idiot, becuase they know you will beat them with a ban stick

You've been around long enough to know that a clue is a clue is a clue. If they don't have enough clue to realize that flaming and calling people 'idiot' is a bad idea, do you really think they have enough clue to realize who it is they're flaming?

[Majin]

let me see, will this get me banned?


WDB

[wdb]

Lucky for you the image is within forum specs.

[Majin]

that was close!

[hwy61]

After reading a lot of info on this, I still don't fully understand it but I have come to this conclusion. Subaru installed a perfectly good computer controlled center differential. They then advertised and added a feature to allow the user to screw with this system without providing any useful information on how, when, and under what conditions to do so. In fact it seems apparent that manually operated in one of the locked positions can actually damage the drive-line components of this car by driving on a hard, dry surface, like a road or parking lot. Did I mention expensive parts.

It sure seems that instead of remaining largely mute on this system and at worst saying you will hear knocking when turning with the center differential in one of the locked modes, but don't worry, this is normal, they should have in fact explained exactly how to use the system and what not to do as many other manufacturers of locking diffs do. I'm still learning about this system but it's off to TopSpeed in Atlanta for a long overdue tune tomorrow. Oh boy, oh boy, 400 whp?, 500 whp? perhaps a million. Hwy61

[hwy61]

Oh yeah, thanks for the input and info everyone. I actually read it all. I really cracked up at posters saying that's bs, this is how it all works and I know what I'm talking about. I've been fooling with cars for over 45 years and they keep evolving faster than I can keep up. I do know how you shut a diesel engine off and some of you don't. I also know the difference between an engine and a motor and some of you don't. I also understand octane, octane rating and the importance in regard to high performance engines and some of you don't. I'll also have 2 million whp tomorrow after TopSpeed gets through with my car and some of you won't. This is a good learning place. Thanks to all. hwy61

[raindance]

I've recently started to mess with the thing a lot. I'll go to a nice curvey little backroad somewhere. Stop, then put it in manual. Dial it to lock, take off and as I accelerate move it toward open. I fiddle with it to see what it will do under different situations (I do this when there's no traffic around and it doesn't distract me too much). If you goof around with it in different circumstances you'll begin to get a feel for it. I've read all the posts about how it does what it does, I've read the '04 and '06 tech manuals about what it does and how it does it (wish I had a copy of the '05 but the other two are close enough). It's slick and it does work. If you're more mechanically inclined, read the tech manuals, they helped me understand it the best.
-rain-

[Antimullet]

I use it alot at the autocross and drag.

Autocross, run it as loose as possible (to the rear) for a slightly loose tail and less push. Unless it rains then its auto.

Drag I like to run it almost all the way loose or a click or two up from loose.

The idea being less power going to the front and causing front tire slip off the line, and less parasitic drag of having a locked as opposed to open diff. This is a balancing act though, too loose and you may slip the rear tires too much, too tight and you may slip the fronts too much off the line.

[Philthy]

I've started to play with the DCCD a bit - based on my driving style in dry conditions, I found that I get a lot of push and torque steer in auto mode - I dial it all the way back (green arrow) and it gets much better - I'm able to go much faster in the twisties in this mode.

Haven't played much with the middle settings yet...

.02

[Nachos Libres]

Originally Posted by Philthy

I've started to play with the DCCD a bit - based on my driving style in dry conditions, I found that I get a lot of push and torque steer in auto mode - I dial it all the way back (green arrow) and it gets much better - I'm able to go much faster in the twisties in this mode.

Haven't played much with the middle settings yet...

.02

The middle settings are more for gravel, ice, and snow, not really for dry tarmac.