wrighty338

iTrader: (33)

From watching the prodrive p2 video c/o top gear

From 3.00 onwards

YouTube - Top Gear - Pro-Drive P2 Test Drive and Stig lap - BBC

If so, this is a huge advantage? and an upgrade that should be considered for sprint/track use surly? I never realised it did this

urban

iTrader: (1)

No thats definately not how DCCD works

I wonder if it will ever appear as an option though?

The rookie

iTrader: (1)

The P2 uses standard components but set up differently to give a degree of active torque control, the wear rates on the clutches will be much higher than in the standard application as its trying to create a torque split, also the differential is 'working' the whol time rather than rotating as one unit as it does in a standard car when driving in a straight line, so I doubt it would achieve the durability required for a production car.

Simon

P.S My mate was working at PD when the P2 was built and built the transmissions for it as he was in the GroupN trans build team.

wrighty338

iTrader: (33)

oh

how does dccd work then lol

Splitpin

Think of the DCCD as two separate components - an open diff with an inherent rearward torque bias and a clutch.

The clutch can either lock the front and rear outputs of the diff together, or it can be disengaged, to allow the diff outputs to do whatever comes naturally. Or it can apply an amount of force anywhere between those two extremes. Rather than being operated by springs and a cable or hydraulics, like a normal clutch, it is electromagnetic.

With the clutch fully open (i.e. off) the diff behaves as it wants, freely able to balance differences in the front and rear axle rotation speeds, and following its natural torque bias under power.

The more preload is applied via the electromagnetic clutch, the "stickier" it becomes - and so the natural rearward torque bias will increasingly be counteracted - up to the point of "lock", where you basically have no centre diff at all. Although, as you'll know if you drive round at parking speeds with the diff "locked", it doesn't literally lock up - you can still make it slip if you load it up enough.

wrighty338

iTrader: (33)

excuse my lack of knowledge i really dont understand diffs and all this r180 type diff and final drive talk it confuses hell out of me

Ok so we have an open diff and a clutch (not normal clutch no?) So a clever Central diff

So with DCCD off the drivetrain will behave like a drivetrain on a non DCCD. and split the power equally? or are they set to deliver a certain % front + rear?

And with DCCD adjusted on (the more 'on' = the more 'stick or lock'?) so the power iv bia's towards the rear?

so what does it mean when a diff is locked? its working more?
and realistically, does a DCCD offer any real gain other then preference as to how the car behaves when the power is placed more to the rear?

Splitpin

Plenty of resources around to read fella. It's probably a lot less complicated than you think. A bit of time spent learning now will probably save a lot more in future.

The operating principle is a little different than a normal clutch, but that is, in effect, what it is - a way of creating friction between two rotating shafts.

Not quite, no. As above the diff part of a DCCD has an inherent rearward power bias - around 66:33, 65:35 or somewhere around there. The other thing to bear in mind is that a non-DCCD Impreza has a viscous coupled centre - so there's still a significant limited slip aspect to them. With the DCCD unpowered there is almost no slip limitation, it's pretty much an open diff.

No, it's the other way round, pretty much. The more power you apply to the electromagnets in the DCCD, the more friction it will apply to the front and rear outputs, and so trying to stick them together - the more it will try to send power to the front axle and the more it will resist a loss of grip at one end or the other of the car causing the power to be spun away.

No, when the diff is locked, it's not working at all - it's like having a solid shaft connecting the front and back axles. This means that as above there's effectively no (or next to no) chance of a loss of grip at one end or the other causing the diff to spin away all the power as would happen with a fully open diff, so in a straight line on a low grip surface you will get better traction than with an open (or with a fairly soft LSD).

It also means that there's no way for the centre diff to mitigate differences in the front and rear axle rotation speeds - as you get, for example, when turning into a corner (the front axle will want to slow down quicker than the rear).

It's not just about feel. Well set up DCCD car is ultimately quicker than a viscous one if all other things are equal - especially if the diff is actively controlled.

wrighty338

iTrader: (33)

right so pretty much the opposite of what i was thinking

thanks for your detailed answers