A few questions about ACD that I can't seem to find the answer on, maybe a few of you might now.

1. Does driving with the ACD switch on a different setting than conditions hurt anything? AKA If I have it on SNOW and I drive on the bare, dry streets, is it going to damage the center differential gears or anything else for that matter? Owners manual doesn't say either.

2. What exactly happens on the SNOW setting vs. TARMAC? I read the FAQ on the ACD, and it says snow setting keeps the ACD locked for longer after a steering input was made, which, doesn't make sense. Or is the car essentially 2WD while the ACD is locked? I would imagine it's the other way around, where 'free' means the rear wheels are being driven during that period?

Driving over Snowqualmie / Blewett pass on Sunday, there was definately a noticable difference while driving with my Advans depending where I had the ACD set, but I couldn't make any logic over what it's doing compared to how the car was feeling.

 

to answer question 1.
the differential setting dosent matter for everyday driving. if you forget to switch back to tarmac after being on snow for example, what those setting do is it makes the differential distribute the power differently if the car was in snow and started to slide out, or if you were on gravel because the two surface are very different. once the car starts to slide or the diff "senses" any of the wheels spin it trys to compensate to give you traction. the setting you choose simply presets the diff for the kind of driving condition you are in. my friends with 05's swear there cars handle better daily on the gravel setting then on tarmac. and none of them have had any problems yet.

for question 2:
i cant explain the mechanical part of how it works but i know the evo is always in AWD the center diff just decides which tire gets how much power and the distribution of that power in everyday driving. kinda like a 60/40 split if it needs more power to the front or visa verse.

if someone knows how to explain this mechanically please step in.

 

https://www.evolutionm.net/forums/sh...d.php?t=175195

 

I've read the entire thread multiple times, that's why I'm confused. When the ACD is in a 'free' state, does that just mean it's acting as a normal differential, distributing torque to the least path of resistance like a normal differential, and once it' 'locks' it equally drives front and rear? Or does free mean it does not engage the rear wheels (as if the Ebrake is pulled? There's no torque split like the previous poster mentioned.

 

the rear wheels are always engaged, that's why if you tow your evo with the rear tires on the ground, your TC is toast.

 

free state means that all 4 wheels are spining witha equal amount of power, when it locks is when it sends different ammount of power to different wheels.

 

I was under the impression our cars are locked in at 50:50 and no side to side variation in power because of the lack of AYC. I'm guessing the center diff stays in LSD mode longer on snow mode than tarmac or gravel to ensure traction while the tarmac setting allows more wheelspin than say gravel or snow.

 

actually the opposite. in snow mode the diff locks slower allowing more wheel slip in the front before locking the front to the rear. thats why you see considerably more power on oversteer in the snowy conditions with the diff set to gravel than you do in snow.

the power ratio is always 50-50, but the rate of diff lockup can (and does change).

 

That explained it... on tarmac, the car was oversteering tremendously in the snow which was getting a bit nerve wracking on a mountian pass with Advan tires. People say drive slow, I say find the limits, then take it down just a notch

 

That really clears it up for me. Thanks Greg. I was wondering why my rear end kept wanting to slide out until I realized I had inadvertently pressed the ACD button and it was on Tarmac mode while it was snowing and the roads were icy.

 

advans in snow=death wish

 

It's all fun in the snow ,no matter what mode your in.

 

hahaha probably true

 

Yup, earlier this week we had, um, some of that white fluffy stuff fall from the sky here in the Seattle area. It was fine in the morning so I drove my car to work with the A-046 tires on. Then I had to drive home in the evening in a winter wonderland. They are NOT all seasons, let alone snow. They have no winter tread. They have no sipes. They get cold and not sticky. The ABS was on most of the time during braking. Its something I don't recommend. Let me put it this way, my Chevy Blazer with 6 year old Michelin Cross Terrain tires warn down to the wear bar indicators had better grip, which still wasn't a lot {grin}