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DCCD setting
I have a 1998 STI type R Jap Import and there is a diff control wheel between the seats which says c.diff on it. there is no manual/auto switch.
does anyone know if - 1. Fully back is this an auto setting ? 2. which is the best setting for everyday road driving ? |
Fully back is more rear wheel drive, quite naughty. I drive with mine one notch forward;)
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I use mine fully back for daily drive, and just into the green/prange for racing on track (hillclimbs).
Wind it back for slow parking etc. |
No auto element to 98 or any classic dccd boxes - fully back is fully unlocked so 66R 34F drive split. fully forward 50:50 (you'll never use that, unless you're bogged down in a muddy field or trying to get up asnowy bank or whatever.
fully open for dry tarmac. two greens or just into orange for greasy wet days |
Not quite right, fully locked still gives a 66/34 nominal torque split (just as a normal 50/50 torque split diff would stay at 50/50 is locked like say some LandRovers), its just any rotational speed difference will mean the torque split changing as the two output shafts fight each other...
As for open being 'more' rear biased, equally rubbish as the epicyclic gear set means its always nominally 66/34 rear biased... Simon |
The more I read about the DCCD the more I get confused! :wonder: :lol1:
Could someone explain in very simple english for a not massively technically minded person such as myself? I was always under the impression that in fully open mode (wound right back, bottom green light) that is in '4 wheel drive mode' (66/34) and wound right forward into the locked position (top orange light) is pretty much 'rear wheel drive'. |
ALL TECH aside:
It's always 4wd, but with controlwheel fully back/open, it almost feels like a RWD (but it's still 36/64, 35/65, 40/60 depending on version) and you're going to spin your rear wheels if trying to climb a muddy slope or similar. Can easily cause oversteer. control fully forward/locked will force both axles to move with equal speed and thereby act as it's 50/50. Good for bad friction surfaces, bad for sharp turns (wheels wants to rotate at different speeds). Will give understeer. |
Its a normal differential, it has epicylic gears (similar to the Audi Quattros and Ford Sierra/Escort 4x4's) which gives a 66/34 torque split, the limited slip function is a plate diff, however it has very little preload, the preload (and therefore also the effects of the ramps) is set by the electronic magnet and this is controlled by the ECU, more clamp = more limited slip function, provide enough clamp and its effectively locked, this does not effect the static torque split one jot, but as with any limited slip diff, as soon as the limited slip takes effect the actual torque split changes.
Not sure it ever acts like its 50/50 (as mine is 50/50 with a very loose VC!), but try and corner off throttle and a locked diff forces a LOT of torque to the front as the rears try and trun slower - result is UNDERSTEER. Simon |
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Originally Posted by The rookie
(Post 7567216)
Not quite right, fully locked still gives a 66/34 nominal torque split (just as a normal 50/50 torque split diff would stay at 50/50 is locked like say some LandRovers), its just any rotational speed difference will mean the torque split changing as the two output shafts fight each other...
As for open being 'more' rear biased, equally rubbish as the epicyclic gear set means its always nominally 66/34 rear biased... Simon Felly's original post of the dccd manual, that that Steven /P20SPOD has helpfully linked to again, says it all for the OP, but if you want loads of technical arguments you could always go to the 50 odd pages of arguments on NASIOC.com that these technical niceties spawned. Ultimately OP, if you leave the diff fully open on a greasy wet bend and accelerate hard the tail will come out more easily and will stay out more than it will when the diff is partially locked- so lock it up a bit in the wet, limited effect on dry grippy tarmac so leave it open - all as Adam K said. |
Originally Posted by Fat Boy
(Post 7568153)
:rolleyes: Technically correct, but,in practice, that's pretty pedantic as all the OP wants to know is what's the best setting for everyay driving. As you say yourself - it's a "nominal split" as the locking effect of the effectively plated centre diff will "mean the torque split changing as the two output shafts fight each other..." so once some lock has been applied and torque is put into the diff it's effectively moved away from the nominal split.
Felly's original post of the dccd manual, that that Steven /P20SPOD has helpfully linked to again, says it all for the OP, but if you want loads of technical arguments you could always go to the 50 odd pages of arguments on NASIOC.com that these technical niceties spawned. Ultimately OP, if you leave the diff fully open on a greasy wet bend and accelerate hard the tail will come out more easily and will stay out more than it will when the diff is partially locked- so lock it up a bit in the wet, limited effect on dry grippy tarmac so leave it open - all as Adam K said. Fat Boy - how many lights forward are recommended for driving in the wet. When I drive in the wet with dial fully back I get wheelspin is this normal ? Also does the car have to be stationary to change the setting. Will it cause any damage to the car moving the wheel when the car is in motion ? |
Fat boy in my opinion and experience racing my Sti V3 with dccd in al conditions to the limit is correct.
You can change the dccd on the move. It's characteristics change as fast as the knurled wheel is moved. I do not use the dash lights on my converted car, too mush messy wiring so have mad a simple device to count the individual ribs (knurl) on the wheel. This gives a very fine dccd adjustment. iirc there are about 20 ribs I count across starting from fully open to fully locked. For the road I use the car in Fully open, I do not try to drive round islands sideways, so this is good for wet or dry for me. Racing in the dry, I advance the wheel 8 ribs from open. The wheel is a simple electrical variable resistor, but its relationship or action with the dccd is not linear. Half way from open to locked is almost 80% locked. Due to manufacturing tolerances/wear and tear, this setting may not be ideal for another car, so expeiment, but use small changes, not big swings of the wheel! I had a hard time with the car till John Felstead told me. I use the same '8 ribs' fo the wet/damp too while hillclimbing with the dccd set just before the start of the hillclimb run and leave it there till I have crossed the finish line and on the move wind it back to open to allow judder free parking. |
Except "Even if the DCCD is set to LOCK (orange), by pulling the hand brake lever, it will automatically go to DIFF FREE, moving all power to the rear wheels" is completely wrong, especially as if the handrake is on, then the power will be spilt 66/34 with the rears locked and the fronts taking their share!
Simon |
Originally Posted by 911
(Post 7569750)
Fat boy, in my opinion and experience racing my Sti V3 with dccd in all conditions to the limit, is correct.
You can change the dccd on the move. It's characteristics change as fast as the knurled wheel is moved. I do not use the dash lights on my converted car, too mush messy wiring so have mad a simple device to count the individual ribs (knurl) on the wheel. This gives a very fine dccd adjustment. iirc there are about 20 ribs I count across starting from fully open to fully locked. For the road I use the car in Fully open, I do not try to drive round islands sideways, so this is good for wet or dry for me. Racing in the dry, I advance the wheel 8 ribs from open. The wheel is a simple electrical variable resistor, but its relationship or action with the dccd is not linear. Half way from open to locked is almost 80% locked. Due to manufacturing tolerances/wear and tear, this setting may not be ideal for another car, so expeiment, but use small changes, not big swings of the wheel! I had a hard time with the car till John Felstead told me. I use the same '8 ribs' fo the wet/damp too while hillclimbing with the dccd set just before the start of the hillclimb run and leave it there till I have crossed the finish line and on the move wind it back to open to allow judder free parking. Given that you have a 98 type R, you'll have the dash lights - so fully back/one green in the dry is fine, maybe come up a little bit if you're going to really press on just for a bit more stability. In the wet - two greens/just into orange, but return it back to open for low speed manouevring/ parking, or as Rookie says just lift the handbrake a little bit ( until the light just comes on) and the diff will go free. Experiment - a track day or an airfield day would be the best & preferably in the wet so you can feel the changes at a lower limit. Above all - enjoy and work up to limit. Cheers FB |
John F sorted my dccd settings a treat, the guy is brilliant in suspension too. The two actions were tuned by John on a private day on a real sprint track, and the difference a small wheel movement makes is remarkable,
and proven and for me totally revealing to the antics of the dccd when really using it to go faster. Set it wrong in the wrong conditions when DRIVING the car hard and you will have a real handful. Some call it exciting, I don't and it robs you of speed. Get it right and it is fab. |
i have just bought and fitted a STI 3 DCCD box and now need a wiring diagram for it - can anyone help????
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Yes, i have one for you to follow, but one question:
Do you really want to fit the stock ecu for the dccd? The Neetronics controller offers a lot more. Wish i had invested in one. The diagram will take some finding in 'email' format. Will have a search. and post on here. |
I have an Neetronics and it's fantastic. They have just included a left foot brake function too :-)
(trigger and level for trottle position, brake, left foot brake, handbrake (0%), slow speed (0%), launch mode, and thumb wheel of course :D ) |
can you give me a link to the Neetronic controller , I have just bought a type R rally car so looking to get as much out of it as I can
Cheers ian |
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