CDR

Am a relatively new owner of a STI RA VI Limited (came from a std model MY99 rex) so am just getting in to experimenting with the settings of the DCCD at the track. Keen to hear what others experience of it are.

Started using it full open to start getting a feel for the car. Found I was getting wickeed power over steer out of the corners. Very good fun but not very fast. Also found the tendency to lock wheels wa quite high with the open centre. (Coming to terms with no ABS as well)

Have now found that about the middle position seems to get the car nice and neutral and has the added benefit (nice surprise) of reducing wheel lock up by forcing the drive elsewhere.

Haven't played with it fully locked, but am heading out to a wet autokhana today, so today might be the day!! The settings above have been used on dry days with a road legal R comp tyre.

johnnynomates

I'm in the same sittuation. For tarmac ralling, i've allways set the diff control to the centre setting. Would it harm the shafts/ diffs if i set it fully locked?
Full diff lock as anyone tried this on dry tar?

stockcar

you'll overpower the front wheels in the fully "locked" position with a std box, as the front has an 'open' type diff.....................all you'll do is induce lots of understeer and wheelspin as the car tries to waste the power you are throwing at it!!
have always found around the central to 2/3rds rear to be the optimum in a std car.................
hope this helps,
alyn - asperformance.com

RRH

I've always used 1st yellow in heavy rain and / or very slippy on track.

Helps massively with the stability.

Much more than the 1st yellow can prove counter-productive.

It will help high speed stability and braking (will probs knock its nuts off under heavy braking though) but, as Alyn quite rightly suggests, it will make the car understeer dangerously.

Never needed to use more than 2nd green on road, first yellow in really heavy rain and standing water.

John Felstead wrote a very good article on DCCD setting a while back- it makes good reading if you can find it.

hope this helps,
simon

ps never used anything other than fully open in the dry- always found I'm quickest like this.

Kane

On track always leave diff free, understeering and bad control can be fixed(Powerstation suspension mods and driving within your limits/track experience) When it started to rain at CC - set to middle was ok while a few RWD cars went off - mine handled fine, did go diff lock for half a lap when it really was bad rain and was still ok as long as you let the car drive in/out of the corners and dont try to over drive it yourself.

SUBTYPER

I am getting GEMS Active Diff controller and will see what it likes but already a great response from MISS SCOOBY.

ScoobySport (SdB)

A good rule of thumb in this (although far from a hard and fast rule) is that you'll get more power-on understeer the further forward (closed) you set the centre diff.

The reasons for this are mainly due to the agressive nature of the rear diff.

The rear diff tends to lock solid almost as soon as any reasonable slip happens. A locked rear diff basically means that the rear wheels are no longer able to roll at different speeds (to cope with the fact that you are going round a corner) so at least one is going to have to slip / lose traction.

The laws of the traction circle dictate that once you've used up all of the available longitudinal "grip" available (due to wheel spin / slip) there is no lateral grip left. This means that whichever tyre is not slipping, is having to do all of the lat acc work and is also trying to do the most work on longitudinal acceleration at the same time.

Meanwhile the fronts are left pretty much untouched and only have to deal with lat acc, making them nice and powerful.

Sooner or later (usually within a few nanoseconds! ) this gives up the ghost too and you're into a world of limit handling and pant filling!


By closing the centre diff a little more, you are forcing the fronts to take some of the torque, causing them to use up parts of their traction circle as well, effectively balancing out the power-on handling.

Locking the diff completely has other issues. You end up relying very heavily of the difference between the front and rear diffs as your handling balance. I am not sure what the differences (if any) are between the front diffs of the different models of scooby with a DCCD, so couldn't comment exactly on how this would affect things, but you are likely to have a very tricky car which understeers badly then snap oversteers, unless you really know what you're doing.

For interest, the most performant set-up on loose surfaces like gravel would probably be the fully locked setting as it gives you the best possible traction, but for tarmac, you might say that the fully open position is the quickest. Of course, all of this changes for different circumstances.

Active is the ideal way to go if you have the time / money / interest, but as with engine mapping, the actual software / engineer who maps the diff is the clever part and should not be entertained unless you know what you're doing.

All the best

Simon

CDR

Seems there are mixed opinions, but seem to agree with most that the 1st orange provides the most neutral handling and the quickest times for me.

Did experiment with full lock, and as expected, understeering pig!

Full open, despite trying to counter steer and feed in the throttle more progressively still felt slower to me. Could put more power to the ground and get better exit speeds with a bit of drive further forward. I also find that without the ABS, the car performs much better under brakes with a bit of lock in the centre diff.

Thanks for all the feedback.

Note: car does have significant suspension upgrades so I dont think this is lacking (upgraded swaybars, links, coilover shocks, anti lift kit, upper and lower braces, chassis lock bolts) and has had a reasonable amount of time spent setting up. Also has been dynoed at 289ps at the wheels which seems to make it a bit more of a handful and highlight traction issues.