mdosu

iTrader: (6)

Hey everyone with ACD's...I was wonder what the splits were for the 3 settings?

Also, I'm just curious, if it's raining, which setting do you put it on?

4-BNGR

iTrader: (3)

Tarmac - 40% front, 60% rear
Gravel- 60% front, 40% rear
Snow- 50% front, 50% rear

In the rain use snow

mdosu

iTrader: (6)

wait, it's not that all the time right? It's split between that and 100%-0% front-rear, at least for tarmac?

4-BNGR

iTrader: (3)

It's really always 50/50. The center diff has a fixed ratio gearing, which is 50/50.
The ACD mode varies the differentials lock state duration and locking power only. So the #'s I gave are an illustrative approximation...

mdosu

iTrader: (6)

ok, so on Tarmac, it's 40%-60% fixed at all times?

so this is a massive change from the non-ACD Evos which is basically an automatic adjustment by the car from 100-0 to 50-50 depending on conditions pre-determined for the car?

sabastian458

iTrader: (25)

just leave it in tarmac when it rains, the only time you change it is if you are in gravel or snow

donour

iTrader: (6)

Um...no. The drive train always keeps at least 50% of the power in the front. The "best" split you can get is 50-50.

As someone else said, ACD settings don't really define a specific power split. Instead they simply control how soon power is taken away from the rear.

d

JoeWalker4G63

iTrader: (6)

If I'm correct the 05 models have the ACD?

DaWorstPlaya

iTrader: (31)

^What he said. It also adjusts itself to different locked states under braking, accelerating and normal use under the different settings. ACD can't do F-40% R-60% split, you must be thinking of the STi. On the driver side door, the sticker says to set it to gravel when it rains. Thats what I do. Its a very complex and cool system. I could definately feel a difference in stability with the different settings.

DaWorstPlaya

iTrader: (31)

yes

Hiboost

iTrader: (9)

From what I can gather from this article the Tarmac settings gives you the most effect where as the snow settings gives the least with gravel somewhere in the middle. I am wondering if there is ever a time that using the snow setting on dry pavement would be advantageous or the reverse. I would imagine that it's effects are subtle but I'm sure they are there for a reason. Having Limited Slip up front now also seems to effect how the car turns once the tires hook up and can really suprise you if you aren't expecting it.

http://www.autoworld.co.za/aardvark/viewart.asp?id=2766

Here is a cut and past of where they talk about ACD but the article was written for the non US models that have "Super AYC" as well. I'm thinking that certain autocross situations where the surface is not very sticky that gravel or snow setting may work better but I'm really not sure. When they say greater stability and less assist that could mean more understeer but also less sudden snap oversteer:



As a reminder, ACD regulates slipping in a 50 / 50 torque split centre differential from free to lock-up, for improved traction performance and steering response through corners.

The Evolution VIII`s AWC system now stretches the cornering envelope further while retaining the car´s natural, driver-friendly handling and behaviour characteristics at all speeds and over all surfaces.

Since Evolution VII, AWC has featured automatic switching between 3 modes - Tarmac, Gravel and Snow – to enable quicker and better control response for changes in road surface. For the Evolution VIII, each mode has been tuned as follows:

In Tarmac mode, AWC is tuned to fully extract Super AYC´s potential to make the car more responsive on dry surfaces. Super AYC and ACD control is feed-forward compensated for driver inputs to realise better straight line speed and feed-back compensated for car behaviour to improve straight-line stability.

The result is that car behaviour is more predictable and corresponds to the driver´s intentions and expectations instantly.

In Gravel mode, AWC delivers the best balance between drive and steering traction – crucial on wet surfaces. Compared with Tarmac mode, Super AYC and ACD feed-back gain is increased to improve traction and stability, while Super AYC provides less turning assist, to deliver cornering characteristics appropriate on wet surfaces.

In Snow mode, AWC bias is tuned for greater stability and thus makes the vehicle more competitive over snow-covered surfaces. Super AYC and ACD control bias is tuned for greater stability than the Gravel mode, while Super AYC delivers an appropriate degree of turning assist.

zstryder

iTrader: (19)

I think we need to have a sticky about ACD/AYC. There have been way too many people coming in asking this question, and/or people answering that you can get 70/30 30/70 splits...