[T3h_Clap]

Originally Posted by JiveMasterT

Sorry but how would that reduce understeer? If you have more torque going to the front won't that increase the chance that they will spin under cornering and then cause you to understeer more?

if you've got your foot in the floor yes it will cause the fronts to slip. by your theory this means all rear wheel drive cars wouldn't ever understeer, which is not true at all. I trust the Subaru engineers know what they are doing when it comes to the Center Diff stuff.

this was done in 06 to also make the vehicle more stable at high speed.

there is a reason the 06 is faster around the track, and it's not b/c of the new hood scoops

[JustinH]

Originally Posted by T3h_Clap

....
there is a reason the 06 is faster around the track, and it's not b/c of the new hood scoops

[flat4t]

counter steer..this helps from spining out...and don't punch it so hard at first you need to feel the car...luke feel the torqe it is your friend...be safe!

[flatthump]

Originally Posted by JiveMasterT

I'm pretty sure they 06 has the 35/65 just like the older ones. There were a lot of changes in 07 like the downgrade of various suspension bits as well as no additional caster, which in turn shortened the wheel base a half an inch.

No it doesnt I promise you.

In 06 it changed to 41/59 and they added a mechanical LSD to aid the DCCD clutch. So even with the DCCD dial turned all the way down to green('open'), there is still a certain degree of lockup from the mechanical lsd.

[wdb]

Sigh, yet another DCCD (mis)information fest.

'06 was the change from 35/65 to 41/59 front/rear torque split.

[JiveMasterT]

edit...
Confirmed...
The addition of the Torsen rear diff in the STi changes things a bit in that it is possible for a 90/10 split in either direction on the rear diff as where with the old type of diff it was possible that it could go 100% to either side. Whether they did this to have less maintenance on the rear diff or because they wanted to help with the understeer issues is something I don't know as I wasn't part of the design team

Originally Posted by wdb

Sigh, yet another DCCD (mis)information fest.

'06 was the change from 35/65 to 41/59 front/rear torque split.

Thanks, that seems to be the concensus around here then I won't question it any more. My apologies.

It does seem that they have made a lot of changes to the DCCD system over the past few years though and handling does seem to be improving.

Originally Posted by T3h_Clap

if you've got your foot in the floor yes it will cause the fronts to slip. by your theory this means all rear wheel drive cars wouldn't ever understeer, which is not true at all. I trust the Subaru engineers know what they are doing when it comes to the Center Diff stuff.

this was done in 06 to also make the vehicle more stable at high speed.

there is a reason the 06 is faster around the track, and it's not b/c of the new hood scoops

My theory doesn't say that, but it does stem from the fact that in a rear wheel drive car you are much less likely to understeer than you are to oversteer. One of AWDs greatest hurdles is getting that front "bite" when cornering under acceleration since the front wheels will tend to spin since the car is leaning backwards under the acceleration. In a RWD car you only have the weight transfer to worry about.

I can see now though how the new center diff's split would help because now you're not throwing the weight of the car back as hard since there is not as much torque going to the grippy wheels which in turn gives the front wheels a "chance" to grab the pavement and pull you through the turn. That would be the ideal setup for totally neutral cornering. From there with weight transfer or the ebrake you can throw the car sideways and all that fun stuff.

Hope this make sense.

[JAYMAC10]

Its like the ATTS (Automatic Torque Transfer System) found in the Prelude SH. Its a FWD car and thus has a great amount of understeer. Honda's solution to reduce understeer was to add a torque transfer case to the front wheels. When the car sensed that the front wheels where slipping or loosing traction in a corner the computer applies more torque to the outer most wheel.

It actually works quite well and does make a difference over the regular Preludes that don't have it!

Same idea with Subaru. Increasing the torque to 41/59 FROM 2006 AND UP, more torque is applied to the front wheels to help aid in cornering. Of course, a lot of how a car corners has to do with how good the driver is!

[Mykl]

Originally Posted by JiveMasterT

My theory doesn't say that, but it does stem from the fact that in a rear wheel drive car you are much less likely to power understeer than you are to oversteer.

I revised this statement to be more accurate. FWD cars can't power oversteer, only power understeer. RWD cars can power oversteer, and depending on size, weight, and power level they may even understeer like any other FWD car. But aside from when you roll on the power, generally speaking FWD cars aren't any more prone to understeer than any other car.

I don't understand why anybody would use anything other than the 'auto' setting in DCCD for pure performance on tarmac. All it does it make you faster. When you manually set it you're making a compromise. If you lock it up, the car isn't going to change directions as easily. If you open it up, the car isn't going to get as much power to the ground when you try to accelerate out of a turn. On 'auto' the diff will be open when you need to change directions and will lock when accelerating out of turns.

Also, the knob shouldn't be seen as a "front to rear torque adjustment knob." Yeah, with it set all the way open, it's going to feel like a mad dorifto RWD car... but if that's what you want then why not just buy a RWD car? You're basically limiting the STi's very sharp edge over other cars in limited traction situations.

If you find that your STi actually understeers on throttle (wtf?), you need to adjust your driving or check your air pressures. If your rear pressures are too high, if they exceed the front pressures, the car may push a bit. When at the track, or at autocrosses, set yourself up to go full throttle as soon as it's time to accelerate. One of the greatest joys of this car is the amazing things that it can do when it's time to throttle out. This is all because of the 'auto' setting.

[Mykl]

More info....

Basically, if you're running full open, the amount of torque your front wheels receive is limited by the amount of traction you have at the rear tires. On the '04-'05 models this number may be quite low. On the '06+ models the difference is less significant since there's a mechanical LSD in the center.

On auto, when it's time to accelerate, after the computer as locked the center diff... the amount of torque the front wheels get is going to be limited only by the amount of traction they have.











And for the 2005's with the Yaw sensor, it should be noted that the input from the yaw affects DCCD lockup ratio as shown below:

[Atomic]

Originally Posted by Mykl

More info....

Basically, if you're running full open, the amount of torque your front wheels receive is limited by the amount of traction you have at the rear tires. On the '04-'05 models this number may be quite low. On the '06+ models the difference is less significant since there's a mechanical LSD in the center.

On auto, when it's time to accelerate, after the computer as locked the center diff... the amount of torque the front wheels get is going to be limited only by the amount of traction they have.











And for the 2005's with the Yaw sensor, it should be noted that the input from the yaw affects DCCD lockup ratio as shown below:

That is great stuff. Helps allot in understanding auto mode. Any idea how this changes with the 06 set up?

[JAYMAC10]

Well its been snowing for about a week strait here in Kelowna! I can tell you that for the first time I have ever driven a Subaru in the snow they are TANKS!!!! Awsome cars!!!

Anyways, I have been playing around with the DCCD and to tell you the truth, I can't really tell the difference between Auto and Full open (all the way back)

I can get the car to fish tale no matter what, and it doesn't do it any easier with it in open vs auto....

Just thought I would mention it... but I will continue to play with the settings. I have yet to try it at 1 click below lock.

However, my understanding is that even at full lock, the torque is still split 41/59 (on my 06) and not 50/50. Its just that in full lock the computer doesn't change the torque based on wheel slippage???

Or am I worng?

Jay

[Mykl]

Originally Posted by Atomic

That is great stuff. Helps allot in understanding auto mode. Any idea how this changes with the 06 set up?

Yeah, when I stumbled on that everything started to make sense.

The '06 is probably very similar to the '04-'05 models, at least in how it electronically adjusts lock.

[Mykl]

Originally Posted by jaydow11

Well its been snowing for about a week strait here in Kelowna! I can tell you that for the first time I have ever driven a Subaru in the snow they are TANKS!!!! Awsome cars!!!

Anyways, I have been playing around with the DCCD and to tell you the truth, I can't really tell the difference between Auto and Full open (all the way back)

I can get the car to fish tale no matter what, and it doesn't do it any easier with it in open vs auto....

Just thought I would mention it... but I will continue to play with the settings. I have yet to try it at 1 click below lock.

However, my understanding is that even at full lock, the torque is still split 41/59 (on my 06) and not 50/50. Its just that in full lock the computer doesn't change the torque based on wheel slippage???

Or am I worng?

Jay

I'll try to explain this correctly...

At full lock torque is going to go to the axle with traction. If all four wheels are on ice, you're only going to get as much torque at either end as the tires can put down, which is probably less than the engine can provide unless this is some really grippy ice. But if the front has enough traction to accept all available engine torque and the rear has no traction and can't accept any, then your torque split is going to be 100f/0r. The front will be pulling the car hard and the rears will just be spinning. I hope that made sense.

So when the center diff is fully locked, that 41/59 torque split number is pretty much meaningless. The actual torque distrubution is based only on how much traction you have between the tire and the ground. This means the torque split is probably jumping around a lot.

[Muffnbluff]

I just got done driving around in some ice/slush/snow and wow what a difference the DCCD makes. Slip it all the way back and the fun in the parking lot can go all night. On the way back home slipped it back into locked and it was like I had to try to make the car handle poorly on the mess of ice and slush.

[rmo55c]

muffnbluff - where did you go? i'm debating some late evening donuts in an empty parking lot around the valley or something =)