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DCCD Info


kamineko
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DCCD: Driver Controlled Centre Differential

This is another big subject, here's a compilation of information.

Useful info and first hand experiance welcome. please no 'i kan do phat dccd skids' spam please, it will be bumped off into general or off topic.


Source unknown, lol

The adjustable centre differential is one of the toys upon the Type R which makes the car desirable amongst Impreza owners. The way it works is by an electronic clutch which engages fluid filled clutch plates and this acts unlike a limited slip differential and more like a mechanical device. In the open condition the Type R handles very like a rear wheel drive car. The differential transfers the torque front and back equally but when one end loses grip (usually the lighter rear end) all of the torque is transferred to the axle that is wheel spinning. An LSD would keep some torque going to the wheels still with grip. Thus the Type R can bite the unwary.

Moving the centre console switch one notch forward progressively locks the differential, and in the fully forward position the differention is completely locked. So why should you not have the diff. locked all the time? You are in effect forcing the drive on the front axle to be exactly the same as the rear. When going round a corner the wheels all rotate at different rates, the ones on the inside slower than the ones on the outside of the circular path. The front turning wheels travel at different rates to those on the rear fixed axle. Driving a Type R with the differential in the locked position on a good grippy surface will cause transmission damage, and the effects can be felt through the steering even when the diff. switch is set only one position forward.

So when should you move the switch? As stated the rear of the Type R can be very lively if you let it get away from you. On damp and wet roads this is more likely to happen, so transferring some of the torque forwards might be advisable. With the slippery conditions the speed difference of the wheels will be compensated for by the overall slip on the road surface. If the surface is gravel or snow then it is safe to move the diff. lock to fully closed, giving exceptional traction from both front and back, something an LSD would never be able to give.


Source: A Japanese book 'GC8 Bible' I scanned

Thumb clickable.

dccd%20page_thumb.jpg


Source: Official or translated STI user manual, I'm not sure

centrediffenglish1.jpg

centrediffenglish2.jpg

centrediffenglish3.jpg

centrediffenglish4.jpg

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  • 1 month later...

Have installed one of the DCCDPro automatic controllers into a car that was intended for gravel use (DCCDPro started developing software for tarmac first then gravel). The install was simple as, just a few wires and mounting a g-sensor. The controller could be used in manual mode (like the early DCCD control) or in full auto mode. Full auto mode was then adjustable for "aggresiveness" (not sure how best to describe it). This worked wonders with the car and was incredible easy to adjust while driving.

i.e. at a Rallysprint when setting it up, the driver was asking me to turn it a bit at a time until the car had the balance he was after. The car could be changed from being rather oversteery to very understeery but it was also constantly adjusting the diff itself depending on how you were driving it.

If anyone is fitting DCCD into a car that doesn't have it as standard, then I'd highly reccomend getting one of these types of units. And would also be an improvement if you were looking to make an early factory fitted DCCD car even better.

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Guest SPANKU

i have a dccd ecu, ver4 sti type gearbox R180 reardiff forsale if anyone is keen?

still waiting for my mate to get back to me if he wants it or not then its up on trademe

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has anyone used, heard about the manual controller that possum bourne motorsport do, with 2 dials one for usual adjustment of the diff and the other for adjusting the amount of lock up under breaking and e brake???? similar price to the dccdpro one by the time ya convert to nz dollar and freight.

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 kamineko said:

anyone have a pic of inside the possum bourne motorsport DCCD control unit? i've heard its a Jaycar labeled circuit board, in which case i'm pretty sure what kit has been used/modified

would be a good experiment

cheers.

thats the same one im talking about. from the *sounds* of it, its worth about $50 to build, and is a lot, lot simpler than the dccdpro device

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i havn't seen one, but i'm going to build one to match the description so far.

i see the track quite often these days. i understand and have to deal with the problems of running a manual dccd on the track, quite keen to play around with a basic system

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 kamineko said:

i havn't seen one, but i'm going to build one to match the description so far.

i see the track quite often these days. i understand and have to deal with the problems of running a manual dccd on the track, quite keen to play around with a basic system

good man!

would be very easy to set up. you'd need a second pwm generator, like the jaycar boost controller kit, then use the brake pedal switch to switch the signal to the transistor that drives the diff between the two signals

according to the oem config it pretty much opens the diff up under brakes

dccd02.jpg

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f'in saved! thanks for that optical!

there are a few ways to approach it, even our 10A pwm motor controller could be tricked into doing the job.

but yeah, pretty much just need the diff opened up under brakes for turn in, and cranking it back up on the exit. trick will be gradual changes of the duty cycle.

i have cheap access to jaycar stock, certainly will play. if i could afford 600 for that dccdpro setup, it would be ideal

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  • 2 weeks later...
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  • 2 weeks later...
 smokn4 said:

does this dccd come "only" in sti's or do the "some" wrx's have them aswell?

only sti ra, and type r in gc8...

Version 8 onward all sti got it i believe..

Actually im just thinking the wrx type r and ra MAY have got it but i have idea on that one just a guess.

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 nt_a_foz said:

Actually im just thinking the wrx type r and ra MAY have got it but i have idea on that one just a guess.

negative from the looks of it- a quick look at a couple of gearbox charts all indicate that they got viscous centers. I concede this is internet truth and im quoting it..

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 nt_a_foz']

[quote name='smokn4 said:

does this dccd come "u]only[/u]" in sti's or do the "some" wrx's have them aswell?

only sti ra, and type r in gc8...

Version 8 onward all sti got it i believe..

Actually im just thinking the wrx type r and ra MAY have got it but i have idea on that one just a guess.

ok...im looking at buying a "97 v3 sti type r" but when i car jammed it it comes back as just a 97 subaru impreza ???, when i qn'd him about it he said "its got dccd, only sti's have dccd" ???

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