floppy dave

guys, after having had lengthy threads going about the problems with my diff i thought i would get back to basics, what are the different ratios on the thumb wheel from lock [red] to off [green] on my STi 5 ?

i took my mate out for a spin today who was amazed at just how easily the back end stepped out when even at cruising speeds as if it was rear wheel drive, which got me wondering?

discuss...........

sg72

What!!!

And cruising speed Is!

Think you better check Wheel/tyre sizes./Pressure. Suspension and geometry.

Mines grips like a good'n even on Open.

Steve.

greasemonkey

The torque distribution of the diff itself is 33/66. When you turn the thumbwheel up, preload is applied to it via the electromagnets, which progressively stiffens, and finally locks it.

Thus, at the "Lock" setting, there will be a 50/50 torque split, but only by virtue of the fact that the centre diff has effectively ceased to exist, and the front and rear axles are now locked together.

Don't forget that despite there being five LED's on the dash, the preload itself is continually adjustable via the roller, so it's not like we can tell you what the torque split corresponds to when any of the particular LED's is lit...

floppy dave

im running standard size wheels and tyres which are at the recommended pressure, the suspension is just fine as it is all STi or cusco parts.....
seeing a weenie manged to make such a mess of his when he span it i thought i betta check, i was going around the island at 25 ish not quick at all, however at my favourite island i can push it around at 70 and not even loose grip?

peccy

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.

greasemonkey

What are you talking about Peccy? This is not how the DCCD works.

The DCCD has an inherently unequal, rear-biased torque split, and while the static weighting of the car is lighter at the back, weight is transferred to the rear under acceleration, thus in practice the rear-biased split provides better traction under power.

While an unloaded axle will indeed spin with a truly open differential, the DCCD still has some preload even in an unpowered state, and the further the roller is turned, the more the front and rear axles are locked together and the less inclined it will be to "spin away" power.

If you're talking about the 'normal' centre diff, while it has a 50/50 inherent torque split, the viscous coupling prevents all the torque spinning away to an unloaded axle by creating friction between the front and rear outputs. Thus, a fair amount of power is transferred to one axle even if the opposite end has no traction at all.

peccy

greasemonkey, was just what i read on the IWOC site, http://www.iwoc.co.uk/jpstir.html???

but if torque is still going to the front wheels when the backs are spinning how come the front wheels dont move when Type R's, dccd equiped cars do donuts?

Donut'ing Type R



[Edited by peccy - 10/21/2003 3:54:36 PM]

ChristianR

iTrader: (1)

see johnfelstead excellent post here :

http://www.scoobynet.co.uk/bbs/threa...hreadID=143750

greasemonkey

The information on the IWOC site is erroneous Peccy, looks like it was written at the time the Type R was launched, before the full SP on the diff became available, and certainly before the author had driven a DCCD equipped car.

As for that video, the outside front wheel clearly is spinning, as the car is rotating mainly around the inside front, which is itslf spinning slightly as the car clearly isn't spinning around a fixed point.

Admittedly though it's hard to work out exactly what the wheels are doing as the shutter speed is set too fast, and the frame rate of the final video is far too slow to convey the motion properly. At one point it looks as though the rear wheels are nearly stationary, even though the tyre smoke clearly indicates otherwise.