So, I have a basic knowledge on how the center differential works. I'm wondering if the settings on here can be modifying through the controller for the ACD.

Example.
settings - power ratios front /rear
Tarmac- 60/40
Gravel - 50/50
Snow - 40/60
(I don't have it in front of me so this may be off a bit)

Has anyone gone down the road of modifying it to run for example.. 80/20, 50/50, 20/80? I don't know the limitations on our stock ACD. I know this is possible in aftermarket applications though.

Any thoughts?

 

What exactly do you want to modify? The ACD doesn't change the power levels, it only changes the way the differential locks in limited traction situations.

 

^ +1

 

Only thing I can think of that can kinda control ACD is:
http://www.amsperformance.com/cart/m...ontroller.html

There was a full ACD replacement piece that acted like a 40/60 splitter for the VIII/IX I think, but it was discontinued.

 

This is worth reading: https://www.evolutionm.net/forums/ev...everybody.html

This mod/reprogram (which I believe is what you are asking) is available for CT9As: https://www.evolutionm.net/forums/ev...time-sale.html

I haven't seen one for the CZ4As but I would imagine someone is at least working on cracking it.

 

OP all wrong info. It's ok, this is getting to be an urban legend in terms of torque biasing. The Mitsu system is an open diff based 50:50 torque distribution ALL THE TIME. We need to qwell these common misconceptions about the way the system works.

Here is a copy of a recent post from EvoXforums where I break it down:


The ACD is a slip governing nanny that works similar to a brake.


Tarmac Mode: Allows a lot of Delta (front rear wheel slippage, meaning differences between front and rear wheels speeds). The logic here is that you have good tires and a good road surface, so grip is going to be decent enough and in physics terms the speed difference between front and rear will never really push the 50:50 static ratio too far out of whack. You want it to be free most of the time to avoid the Torque scrub effect and provide sharp turn in.

Gravel Mode: Medium amount of Delta, maybe 10% between front and rear allowed. The idea here is that slippery surfaces will cause the open diffs to send power too quickly to spinning wheels, so the nanny is going to more aggressively clamp at a sooner time to make sure a higher maximum torque makes it to the ground.

Snow Mode: Nanny is on steroids and has turned into a German. It's basically lock 50:50 as soon as there is any slip and allow no slip subsequently unless your turning, and even then it's far less than either alternative modes.


In drag racing either Snow or Gravel is a good idea because we want no spinning wheels. Problem is the system is not active until slippage occurs, meaning any time the ACD activates it bleeds power off the drive line, similar to an actual brake. Torque is converted into heat. It can be as high as 8% of power while the ACD is fully clamped.

So drag racers use Gravel as an intermediate point, allowing a little slip while not scrubbing too much torque off. Snow is so aggressive that, in addition to bleeding the most amount of torque, sends a huge shock into the drive line on a hard launch because there is no where for the power to go without slippage.

Someone asked about ACD tuning, it is possible and has been done for years with previous Evo's. Some companies reflash stock AWC control units and others provide complete programming (Motec, GEMS, etc.) If you take an Evo X RS, an older USDM Evo 8-9, or an Evo X with the AYC deleted then you can tune it quite easily. Your only dealing with a few tables that govern Delta (WSS info), steering angle, and G sensor data, throttle %, and when the brakes are on and off. The idea is to govern when it clamps, the % of clamp, and the % of slip allowed during turning, and how the diff works when braking and turning.

The problem comes when the AYC is added into the mix. Now you have to consider quite a few more tables and a whole new world of physics. No one tunes this yet because there is little empirical data on how the settings effect the car. You can easily fly off the road just tuning an ACD car without AYC, adding torque vectoring is cooking people's brains.

 

I thought ACD controlled the slippage between the two front wheels. As in an Active front Center Differential. (And AYC does the same for the rear wheels). And the front rear split is a consistent split with no change unless you change your hardware. Ie 50:50 lock full/half/minimum throttle.

 

No, there is no active properties in the front.

The ACD is a wet mutli-clutch disk pak that sits inside the Transfer Case. Also in the transfer case is the front differential and parts of the power transmission for the center differential. The actual center differential sits in the transaxle, be it 5MT or SST.

The front differential is passive, meaning it is a simple gear dirven limited slip diff. It has no computer controlled properties. The center differential is controlled by the ACD clutch pak, which is a single pak of clutches dedicated to evening out differences in front to rear Delta. It is physically connected to the shaft that connects to the AYC and the shaft that connects to the front differential.

The three Tarmac/Gravel/Snow settings effect the ACD in the sense of clamping properties as described in my previous post.

AYC has two clutch paks, one dedicated to the left rear wheel and one to the right rear wheel. It can "torque vector", which meaning it can send any amount of power to either rear wheel, from 0-100 or 100-0 (or anything in between) based on several parameters. Most important paramemters are steeering angle, throttle %, WSS data, and lat/long accel.