tarmac/gravel/snow

[HoLeeRay]

we didn't get AYC over here in america

[JR4JC]

how does the evo's diff and all compare with the sti's????

[JR4JC]

bump

[JoizeeX]

i may be wrong, but i think in sti the switch changes the actual torque split from 50/50 to 65/35 f/r? But in the evo, like mr. wong from hong kong said, it changes the duration of locking, that's why it locks for a short period on tarmac setting, since you have lots of grip and don't have to worry about stability as much.

[timmiii]

is it possible to stick a JDM EVO VII t-case into the EVO VIII 5-speed tranny?

[nsnguyen]

The STi diff is mechanically geared to 35/65 F/R, but as the clutch plates lock and limit the differential action it approaches 50/50. Of course the magic is in the details (the programming and actual capability of the clutch packs) so there's no way to know which system is 'superior'.

I would be very interested in seeing an 04RS vs an 05RS on a road course (on the same day) to see what advantages the ACD confers on tarmac. I suspect not that much in expert hands. From the SAE doc posted before, it seems like the primary advantage of ACD is in split Mu situations where the front and rear axles have significantly different amounts of traction, in which case the ACD can lock up nearly completely whereas the VLSD allows more slip to the axle with less traction.

['ringmeister]

Originally Posted by raywong

Tarmac: 50/50
Snow: 50/50
Gravel: 50/50

The center diff has a fixed ratio gearing, which is 50/50.
The ACD mode varies the diff's lock state duration and locking power only. In the entrance of a turn, the diff change from open to lock to provide lateral stability. In the middle of the turn, the diff opens to induce turnning. In the exit of the turn, ACD locks the diff again to provide maxium exit stability.

Tarmac: the ACD stay lock for short duration
Gravel: the ACD stay lock for medium duration
Snow: the ACD stay lock for long duration, lowest locking power.

-this is the best, most accurate description i have heard. i believe the torque split is 50/50 fixed regardless of mode. ACD actively locks and unlocks the center diff, as opposed to the passive viscous diff in the 03'/04'.

[dino21]

its simple to find out.
try when is really snow on the road and you have lots of space.
try tarmac ,turn the wheel full on right or left and accelerate (try harder than ussual)-youll see it feel like rear wheel drive and you get right away understeer .
and then go for snow do the same thing and you wont get understeer,you will go straight through front wheels,and the gravel is something in between.

[fueler11]

I am no expert, but somewhere on this great site I remember reading something very much like what ringmeister described above. I understood it as the clutch pack inside the acd, which is controlled electronically by a cpu, is enabled and disabled at different timed intervals depending on what position the acd switch is set to.

When I got my car I wondered how it would react while driving. So I drive the same road home every day, it was raining here in Oregon like it does, so in this same corner I had it on tarmac and about half way through I accelerated, turbo spooled up and I was 4 wheel drifting. Front and rear breaking loose at the same time. Gravel setting the next day had the rear breaking loose first, slide was predictable, snow didn't have as much difference. I felt the front end pull, but not push as much as I thought it would do. I know, not much of a scientific explanation, but I wanted the "simple" way to find out as dino above said. I have an 06 mr.

[Evo_Kid]

Originally Posted by dino21

its simple to find out.
try when is really snow on the road and you have lots of space.
try tarmac ,turn the wheel full on right or left and accelerate (try harder than ussual)-youll see it feel like rear wheel drive and you get right away understeer .
and then go for snow do the same thing and you wont get understeer,you will go straight through front wheels,and the gravel is something in between.

Originally Posted by fueler11

I am no expert, but somewhere on this great site I remember reading something very much like what ringmeister described above. I understood it as the clutch pack inside the acd, which is controlled electronically by a cpu, is enabled and disabled at different timed intervals depending on what position the acd switch is set to.

When I got my car I wondered how it would react while driving. So I drive the same road home every day, it was raining here in Oregon like it does, so in this same corner I had it on tarmac and about half way through I accelerated, turbo spooled up and I was 4 wheel drifting. Front and rear breaking loose at the same time. Gravel setting the next day had the rear breaking loose first, slide was predictable, snow didn't have as much difference. I felt the front end pull, but not push as much as I thought it would do. I know, not much of a scientific explanation, but I wanted the "simple" way to find out as dino above said. I have an 06 mr.

Do you both know this thread is over 4 years old??

All the info in this thread is wrong because it from 04-05, right when the ACD got to the US and people didnt know anything about it. There is a sticky in one of the sub forums here that properly describes how the ACD works.