Since the STi has an adjustable DCCD (Driver Controlled Centre Differential), what would be the best configuration for 1/4mile launches? 50/50, 65/35, etc....

 

This is a great question. I was thinking about this also. I would "THINK" off the line 50/50 then after second gear get it as close to 2 wheel drive as you can.

 

i d say more to the back is better.

considering skyline GTR. on straight line accelaration

transfer majority ( 90 % or so ) to the back wheel.. as it has more grip..

i think DCCD AUTO mode will do fine

 

Well, if a 50/50 weight distribution in the 325iX calls for a 37/63 split for full acceleration under launch.... the nose heavy, yet more powerful, WRX STi should require the same or less. I seriously doubt you'll be able to vary the torque distribution more than 65% to the rear.

Remember, the impreza platform started life as a FWD compact and handles accordingly. With a 50/50 split in the current WRX, the majority of the weight is over the front wheels, which means overall handling is reminiscent of a FWD with the benefits of AWD. If you want to know the difference.. go drive a RWD based AWD car like the 325iX hard through some turns.. it behaves like a RWD with the benefits of AWD... anyway, that's beside the point.

If a car is built off of a FWD platform, then the best course of action for a variable center diff is to only really vary one axle... so you drive the front axle directly off of the transmission and only vary the rear.. which would mean 0-50% torque to the rear with 50% at full lockup.

This is all estimation though, from knowledge of several AWD systems.. I haven't heard yet what the claimed adjustable torque distribution will be on the WRX STi.

 

I'd think you would want to put as much power to the rear wheels as you can, 65% being the max on the DCCD I believe. When you accelerate, the center of weight distribution shifts toward the back, so that's where you want most of the power. Plus you'd want as much power going to one set of wheels as possible so more of the power is going to the ground rather spinning more rotating mass. All of which might combine to make about .1-sec difference.

 

Is it possible to get 65% of power to the rear? I thought that 50% was max. I know that 65/35 is possible, but considering the FWD format, I didn't think 35/65 would be possible.

 

I sure hope so. If you can't move more than 50% of the torque to the rear wheels, it's hard to see the benefit of a DCCD over the standard VCD.

 

Good to know.

 

I would like a little bit of slip. I bet the WRX does better off the line with the 16 inch potenza re92 than it would with the BBS 17's and sticky tires. Not so much bog off the line. So my vote is for the auto set up on the DCCD, let the back or the front wheels slip a little then let the transmission put the power where it needs it.

 

Just to let everyone know, heres the specs on the DCCD.

There is an auto mode that varies the torque distribution from a cumputer control.

The driver can manually adjust the torque split from 50/50 lock, to 35% FRONT / 65% REAR.

There you have it, sounds like tons of fun to me, and in my opinion: 50/50 off the line, then in second gear, or after the shift to third, go to 35/65 for the remainder

 

Wow! Can't believe the lawyers let that through to the States. There's gonna be some wrecked STi's on Ebay for sure.

Powerful, rear wheel torque bias with a noseheavy car in the inexperienced hands of many owners (I'm not pointing the finger at any of you guys, many of you are enthusiasts). Keep it in 50/50 if you're trading your civics in guys

 

I agree. Performance numbers would be even better with 16's.

But when you're running head to head with an "enthusiast" next to you, is it really that easy to switch the DCCD on the fly or in between shifts?

 

yes it is! its a small dial in the center console only inches from your hand after the shift to second gear!

 

As you accellerate, the majority of the weight of the car goes to the back of the car. This is why the FWD drag racers put on the wheely bar thing on their rear, to keep some of the wieght of the car on the driving wheels.
The DCCD sounds cool for one thing, kickin yer butt out on a turn by maintaining power to the rear wheels consistantly throughout the turn.
I could be wrong on this but it sounds like the Auto setting on the DCCD is alot like what the VDC does?

Incidently, I was at the dealership (Denver) yesterday.
It's funny how uninformed these guys are. Tell me if you have heard otherwise but what he was saying is that the STI will be a 35K hot rod, base model without carpet or a stereo. He was also under the impression that the DCCD will be fully adjustable, 100% FWD, RWD or anything in between. It is truly disapointing what you get when you ask these clowns for info.

Parden my newbee rant, that's just my opinion, I could be wrong.

 

If you want knowledge of a specific car, here's who you ask, in approximately this order:

1) the manufacturer
2) knowledgeable owners/enthusiasts
3) car magazines
4) internet sites like this one
5) someone who owns one
6) your neighbor
7) your cat
8) your navel
9) a tree stump
10) a car salesman