A friend with an 09 RA tried a donut today on a dry road.
He was driving in 1st gear about 5000 RPM, pulled e-brake and turned the wheel left, car got way sideways. At that point he mashed the gas and WOW the car really started to rotate (I was riding shotgun) getting his e-brake hand back on the wheel he accidentally shifted to second (stupid paddles) at which point I think the rear tires and maybe even the front right tire quit spinning and only the left front was ROASTING!! Naturally he hit the brakes and stopped immediately.

Here is my question............how do you get the MOST REAR torque bias?
The car was in Tarmac mode with the stability control off.
Which mode has most rear torque bias...Tarmac, Gravel, or Snow?

 

you can't. it's 50/50 power split all the time. you have to know how to power slide/AWD drift to get the back to kick. or get an Sti. lol

P.S. try this on a track.

 

Heres some info from a mitsu site...

"Using sensors, ACD regulates slippage in the 50:50 torque-split diff from free to lock-up according to speed and load. So under hard acceleration the ACD moves towards lock-up to put more torque down on the road for stronger traction, but with rapid steering inputs it operates virtually like an open differential to improve steering feel and response.

A choice of three setting - tarmac, gravel and snow - operated manually, gradually lock up the Active Centre Differential depending on road conditions."

 

The most you can transfer to the rear with the stock ACD ECU is 50%. Here is a link on the ACD to better understand how it works. ACD Article

 

hey guys dont you remember that someone did the test of all the modes in the snow? i forgot who but it was a demo on the snow and switching the modes between tarmac, snow, and gravel. According to the tester guy he said tarmac was mostly rear wheel power, gravel was 50/50, and the snow mode was mostly front wheel. I could swear thats what he said, correct me if im wrong.

 

Snow has more bias to the rear -- at least that's how my car drives. This is extensively explained in the following thread (my understanding is that the US Evo IX ACD is directly comparable to the 2009 Ralliart's ACD):

https://www.evolutionm.net/forums/ev...everybody.html

 

its 50/50 all the time, the reason you feel more frontwheel in snow is because the acd acts like an open diff more of the time based on steering inputs when in snow mode, and you can accelerate the hardest on paved roads so it would seem more rear wheel oriented since the ACD would almost always be locked, you cant interpret how it feels to you as where the power is being delivered, its 50/50 geared...cannot be changed...period

 

I don't get that -- when the front wheels are spinning freely for longer with the SNOW setting it feels more rear-wheel to me -- more of the traction is in the rear when the front isn't grabbing. The fixed 50-50 split isn't real torque applied to the road, it's torque on the shaft, isn't it? Presumably a lot of that torque can be wasted spinning the front wheels against ice/snow. Ditto when your front wheels are spinning more in a turn.

Very possible that I'm mixed up here -- just feels more rear-wheel to me in SNOW than in TARMAC, at least when I'm driving on ice or snow (very limited experience with slip in turns on dry pavement -- I have snow tires on that screech ridiculously loud when they slip on bare road).

 

In reference to what JON was talking about. Here you go:

http://www.youtube.com/watch?v=BB_IRFnOf_Q

 

That was definately the most informative that I have seen.
My friend is still not sure what setting to use for drifting/donuts on dry pavement.
He likes the extra delay for the ACD to unlock when in snow mode but he also likes the extra clamping force in Tarmac mode.

 

If the front wheels are spinning due to a lack of traction, the center diff will lock up, so it will spin the front and rear axles at the same rate. Being that there is limited traction in the front, the rear axle (assuming it has traction) will be seeing most of the load, effectively making it rear wheel biased, even though the same amount of torque would be available at the front. Of course, this works the other way around. So, if the rear wheels had no traction, the center diff would lock up, and would end up being front biased (assuming the front has grip).


Also, the outer front wheel shouldn't have been roasting with the nice limited slip diff they got in the front.

 

I'll have to go back and look at the marks on the road again but the car felt "hooked up" all of the sudden even though there was at least still one tire still spinning. I am 100% sure the left front was still spinning which during the turn was the inside front tire so you are absolutely correct that the outside tire wasn't roasting.. It is possible that the one of the rears was still spinning but I doubt it. I know this problem can only be solved with more "practice" but of course this practice is expensive so I am trying to learn as much as possible without unnecessary smoke or damage to any of the differentials.