TommiM

iTrader: (19)

Ya, I have autox videos showing otherwise.

-Jarred-

iTrader: (1)

Man that video is an embarrasment. I apologize on behalf of NZ.

17pstockcar

Yip i agree.

Bushpig

so the power from engine should goes to center diff, then goes to front and rear at the same time, right?

or it power the front axle first -> ACD -> rear axle?

Yogi_B

YEEEEAAAAAAH BOIIIIII *stupid hand signs*

TommiM

iTrader: (19)

In a sense your correct for both. Power is 50/50, but whatever mechanical power losses/slip will probably allow one part of the system engage slightly before the other.

For example, the transaxle is bolted right up to the engine and has a shaft going out to a wheel directly so I would imagine that section of the drivetrain getting the power out just a tad bit sooner. Now you add a transfer case and a ecu controlled acd center diff and a rear diff with LSD, now you have an imperfect system that is impossible for everything to get exactly its percentage of power in the same milliseconds as the opposite corner, and that's assuming the engineers have programmed the acd ecu to do just that in any given situation. Maybe the acd maps were designed so in the case of traction loss, as shown in that video the power would be delivered to the wheels as was shown, idk.

evo8426

iTrader: (27)

Looks like the guy bogged a little bit on his tractor pull and that was the hesitation.

Dallas J

iTrader: (1)

Torque is only one part of wheel spin. The evo is a 50/50 system f/r and l/r. Think of a RWD car pulling out of a corner lighting up the inside rear. The rear diff isnt biased in any direction but still one wheels spins. Same happens on the evo except both F/R and L/R and the fronts when launching are unloaded more than the rear.

barneyb

When I was in seventh grade, at the back of my science classroom was an automotive differential, cut open so you could see the gears move. I liked to play with the thing and one day a light bulb went off in my head and I understood how differentials work.

So, there's two camps of people; people who understand differentials and people to whom differentials, LSD and AWD remain a mystery. On occasion I've tried to explain how differentials work but words don't suffice. You gotta play with one. Hence, questions like the OP's keep coming up.

AndyCT9W

I can accept how a differential works if I don't understand it. ACD, however, bugs the crap out of me. The word Active indicates that something will change given certain conditions, but the torque split is static. What changes is the amount of slip given between the front and rear. If the amount of slip in the differential was dynamic would the torque split not also be dynamic?

Note: The above contains only regurgitation of what I've read in the past, nothing I know is true.

Bro my NA 2.0 AT Cef will eat what ever you have! :Car noises: Vraaaap!

llDemonll

iTrader: (21)

someone needs to do a good writeup of what the three different ACD settings do.

There is one writeup, but really all it does is say "uh, the acd clamps at different speeds depending on what setting it's on". that is unhelpful

BEKevo

iTrader: (2)

^ Yea I saw that writeup, on this site.. Not very helpful. Here is some great literature, written by the engineers who developed Mitsubishi's infamous all wheel drive system.. Doesnt get any clearer than this. The concept of Mitsubishi's all wheel drive system is difficult to grasp at first and is considered "unorthodox"(1) to many.. (jack@jackstransmissions(1)

Enjoy.



--The research & development of the AYC/ ACD systems have "expanded the limitations of cornering performance"(MitsuMotors).. The ACD is a very potent advantage in motorsports, in terms of cornering performance, so potent/advantageous it got us (ie Evo's equipped with ACD, ACD & AYC) kicked off the WRC circuit years ago..

BEKevo

iTrader: (2)

This is taken from the article that I posted above.

ACD

"In light of the factors described thus far, a highly reliable bevel-gear-type center differential with a front/rear torque distrubution ratio of 50:50 was adopted. Also, steel plates, which offer high dependability under conditions of high pressure, were specified for the hydraulic multi-clutch, which realizes a high differential-litimiting-torque capacity of 2000 Nm"


This answers some questions that were posted previously.

kikiturbo

to put it simply, evo with ACD works in a following fashion:

1. there is a normal open diff mounted in the gearbox that works as a centre diff. It splits the torque 50/50 front and rear. Both it's output shafts go into the transfer box (where you can also find the front diff and 90 deg "transfer gear" that takes torque to the rear). Being a open diff, it will allow for different speeds of front and rear axle while keeping the same set 50/50 torque between the axles.

2. In the transfer box both front and rear output shafts go into the right side of the transfer box where both are connected togeather trough a set of multiple steel plates. These plates provide resistance to relative difference in speed between front and rear output shafts. The ammount of "resistance" is relative to the pressure that is applied by a hydraulic piston onto the clutch pack. Since the hydraulic piston is controlled by a ACD ECU, we call the sytem Active.. as in Active centre differential. In other words, by clamping onto the clutch pack, we can transfer torque between the two axles.. BUT WE CAN ONLY TRANSFER TORQUE IF THERE IS A DIFFERENCE IN SPEEDS BETWEEN THE FRONT AND REAR AXLE

3. If the car is driving normally in a straight line, there is no difference in speeds between front and rear axles. However, if we get a loss of traction on one axle, then by clamping on the centre diff we will transfer torque to the axle with better traction, or even more simply put, we will increase the ammount of traction the car has..

4. It gets more interesting in the corners... In a corner the front and rear axles do not run at the same speed.. So, if we "open" or "close" the central diff we can, in effect, transfer torque between the front and rear axle even if we do not have a loss of grip.

By actively managing the pressure on the clutch pack, we can fine tune the balance of the car... By closing the central diff, we get more understeer, but more grip also.. Opening the central diff, the car will tend to oversteer more..

Normal programing of the ACD usually opens the central diff on corner entry, to provide for better turn in, and then closes the diff on corner exit. The speed at which it opens and closes the diff depends on the ACD program you choose. That is why in SNOW mode the car is more neutral and slower to change the direction.

Also, the ACD takes into account G sensors on the car, steering wheel angle, throttle position, etc..
As you can see, there is much greater refinement in the way ACD works, in relation to normal viscous diff, and greater scope for fine tuning by ACD reprogramming..

Bushpig

thanks a lot guys! It's really helpful!
Now I start to understand why evo>sti

Btw, is it true that 4g63 can produce more horsepower than 4b11(because iron block)?