DCCD Torque Split

[Dean]

Originally Posted by cody

http://velozt.com/elements/tech/sti/.../DCCD_FAQ.html

Welcome to post #6...

[cody]

my bad.

[A1337STI]

Oh hey so Scott, what do you think of this song now? How does getting Pwned like a noob feel?

thanks for that pdf Mike, that's similar to the one i had on my old work computer, but the one i had actually explains what the cpu looks at to change your locking rates (torque split)

As you get off the gas and brake it expects a corner and opens up the diff, as you turn it it opens it up a bit more, and as you power out it starts to lock it. fully locking it when your steering is straight and WOT.

BTW this song is really good, anyone else have a chance to listen to it ...
*sings to him self* "I'll play with my toes, and still be better than you ... "

[A1337STI]

PWNED /w th3m3 song!

Anyone down for some Computer Games? CSS? Rfactor?

[ScottyS]

[sperry]

So, does he get banned for insulting the board owner? Or banned for post whoring? Or banned for once again derailing a technical thread? Maybe for general retardation? I'm all for votes from the contributing members that are tired of this thread-back-from-the-dead crap like I am.

And for the record, Alex, you still cannot change the torque split of the center diff... it's made out of gears. It's not a transmission, it's not a CVT, it's not electric motors... it's gears, with a 35/65 ratio. I'm still under the impression that you can't ever get more than 35 of the engine output to the front wheels, but there's a decent argument to the contrary (not that you contributed in the least towards the technical discussion) based on the locking of the clutch. But either way, that knob never turns the car into a FWD or RWD car, nor does it change the ratio in the diff. Oh, but I'm sure you meant "torque levels as seen by the wheels" when you quoted that C&D article.

And FYI, the diff works a lot better when it locks up during braking as it balances the braking force through all four tires, but I'd rather not spin out while braking. Not that I have a programmable DCCD controller and 1000's of track miles with it or anything... I'm sure you know so much more about this 'cause you read the STI brochure and hit a rallycross or two.

[knucklesplitter]

With 0 hours of track time I disagree. But from obsessing over the drawings, photos, etc. my conclusion is that when engaged, the clutches (be it 10% or 100% or whatever) will lock the center diff. at 50/50 until some differential torque (ie. loss of traction) between front/back overcomes the clutches at whatever duty cycle they are being driven. I do not know what that torque is.

You can get more than 35% at the front wheels - it will be 35% of the total torque plus whatever torque it takes to overcome the clutches (well sorta). And vice-versa for the rear too. This is described by that table "Here is a table that summarizes this:" in the DCCD FAQ article linked. Note the torque to the rear is more that 65% when the clutches are engaged (and this is an extreme example where the front is on dirt and the rear on pavement).

[AtomicLabMonkey]

Originally Posted by sperry

So, does he get banned for insulting the board owner? Or banned for post whoring? Or banned for once again derailing a technical thread? Maybe for general retardation? I'm all for votes from the contributing members that are tired of this thread-back-from-the-dead crap like I am.

My vote is a ban for general retardation. Sorry dude, but the imaginary theme song and excessive use of the word "PWNED" pushed me over the edge.

[sperry]

Originally Posted by knucklesplitter

With 0 hours of track time I disagree. But from obsessing over the drawings, photos, etc. my conclusion is that when engaged, the clutches (be it 10% or 100% or whatever) will lock the center diff. at 50/50 until some differential torque (ie. loss of traction) between front/back overcomes the clutches at whatever duty cycle they are being driven. I do not know what that torque is.

You can get more than 35% at the front wheels - it will be 35% of the total torque plus whatever torque it takes to overcome the clutches (well sorta). And vice-versa for the rear too. This is described by that table "Here is a table that summarizes this:" in the DCCD FAQ article linked. Note the torque to the rear is more that 65% when the clutches are engaged (and this is an extreme example where the front is on dirt and the rear on pavement).

My track experience tells me that having the DCCD engage under braking decreases braking distance, as it adds stability and helps prevent lockup at any one corner.

As far as how it works, I'm still confused. It seems to me that having a clutch physically lock front to rear would result in a clutch that would wear out quickly and would need to be a consumable and serviceable part. Perhaps that's why running the DCCD at 100% generates so much heat, and why you shouldn't do it except on loose surfaces, but I'm still not convinced that's the way it works.

[Dean]

I think the reason it doesn't wear out is that it is only having to work against a very small speed differential between the input and rear wheel speed which as we have discussed is where most of the torque is going anyway.

It is not like you Exedy trying to make up thousands of RPMs of differential at max torque.

I think the heat is more likely coming from the LSD clutch, but could be mistaken. I can't remember which clutch pack has more surface area. Whichever it is, that's the one making the heat.

[knucklesplitter]

Originally Posted by sperry

My track experience tells me that having the DCCD engage under braking decreases braking distance, as it adds stability and helps prevent lockup at any one corner.

As far as how it works, I'm still confused. It seems to me that having a clutch physically lock front to rear would result in a clutch that would wear out quickly and would need to be a consumable and serviceable part. Perhaps that's why running the DCCD at 100% generates so much heat, and why you shouldn't do it except on loose surfaces, but I'm still not convinced that's the way it works.

I don't disagree with the braking thing, just the always-35/65-no-50/50-ever thing.

Clutch wear is minimized by three things I can think of:

• In Auto the ECU probably keeps it open as much as possible (but I don't know this for sure).
• As Dean mentions the speed difference is usually not much.
• These are wet clutches bathed in the lube that lubes the planetary gears (I assume). Synchronizers are basically wet clutches and last a long long time under more stressful conditions. LSD clutches are even more similar.

[A1337STI]

I honestly have only thought briefly about if having some center diff lock during braking would help or not. As i don't have many track hours to use to aid me to come up with a good guess.

I'm sure what the cars computer does on Auto is geared for keeping the car in control.

Seems like some people think the torque changes and others don't. It is a very complicated system and no one document seems to answers the majority of the questions about it.

I have driven a lot in loose surface conditions with a variety of Center diff settings and I've felt how different locking rates affect the cars traction and handling aspects, though at lower speeds. And while that experience doesn't qualify my opinion as any better as anyone else's , It really leads me to believe one way until I've come across some literature that conclusively shows otherwise. (Perhaps with lots of pictures for my benefit.)

[100_Percent_Juice]

Tell me you didn't post on this again.

[Kevin M]

Originally Posted by A1337STI

I honestly have only thought briefly about if having some center diff lock during braking would help or not. As i don't have many track hours to use to aid me to come up with a good guess.

I'm sure what the cars computer does on Auto is geared for keeping the car in control.

Seems like some people think the torque changes and others don't. It is a very complicated system and no one document seems to answers the majority of the questions about it.

I have driven a lot in loose surface conditions with a variety of Center diff settings and I've felt how different locking rates affect the cars traction and handling aspects, though at lower speeds. And while that experience doesn't qualify my opinion as any better as anyone else's , It really leads me to believe one way until I've come across some literature that conclusively shows otherwise. (Perhaps with lots of pictures for my benefit.)

Right. The Earth is flat until you can personally orbit it.

[100_Percent_Juice]

Originally Posted by BAN SUVS

Right. The Earth is flat until you can personally orbit it.

Oh I imagine he is orbiting earth as we speak.

[M3n2c3]

Originally Posted by BAN SUVS

Right. The Earth is flat until you can personally orbit it.

There's plenty of literature to prove conclusively that the earth is not flat. With lots of pictures for everyone's benefit.

[Kevin M]

Originally Posted by M3n2c3

There's plenty of literature to prove conclusively that the earth is not flat. With lots of pictures for everyone's benefit.

[Dean]

Originally Posted by M3n2c3

There's plenty of literature to prove conclusively that the earth is not flat. With lots of pictures for everyone's benefit.

Yeah, and next you will be saying we landed on the moon... HA!

Edit: Dang, I just polluted a tech thread. I was trying not to do that...

[cody]

Originally Posted by sperry

http://velozt.com/elements/tech/sti/.../DCCD_FAQ.html

Anyone have links to part 2 and Part 3 of this article?

[Dean]

Originally Posted by cody

Anyone have links to part 2 and Part 3 of this article?

I looked pretty hard and couldn't find them. They may never have been written.

[cody]

Okay, thanks.

[wrxkidid]

peace love and happiness....