I think i've read every thread on here about ACD and I have one question. How can the ACD have control over the "locking" of the diff and have zero control over the torque split? By definition if the front and rear are locked together then you could apply 100% of the engine torque to one axle and thus have a torque split of 100%.

 

if the front and rear are locked together, then it's applying 100% of the torque equally to both the front and rear axle's (or a 50/50 split in torque because thats how the teeth are set up). Then when it unlocks, it lets the torque goto whatever it wants to just like in an open dif.

Terry S

 

If you lifted the rear wheels off the ground and the acd was locked it would put 100% of the torque to the front wheels and 0% (neglecting frictional losses) to the rear wheels. It certainly isn't applying 100% of the engine torque to both the front and rear wheels at the same time, otherwise you would have 200% of the engine torque available. Obviously not possible.

 

Griceiv -

You are thinking about it correctly. Open diff = 50:50 split. Locked diff = up to 100:0 split as in your "rear tires in the air" scenario.

 

nice

 

A lot of regular LSDs under such condition would apply ZERO torque to either
wheels. So if ACD is indeed acting like an LSD, you might not get any torque to
any set of wheels.

Edit: Never mind, I think this only applies to gear type LSDs.

 

Most LSDs do this...

Open diff = 0% lock up = 100% tq to the side with least resistance
100% locked, welded diff = both set of wheels spinning the same rate

or in term of tq split...

shouldn't

open diff = 100:0 or 0:100
100% locked = 50:50

????

 

Correct. With the diff. "locked" your torque split has everything to do with the traction you have available at each tire. With the diff open, your torque is split 50/50, with the maximum amount of torque available determined by the set of wheels with the LEAST amount of grip.

 

Reverse what you said and that's the way it works. IF the front and rear are locked together, who knows what your torque split is? It all depends on the levels of grip available. As mentioned above, if the fronts were on tarmac and the rears were magically in the air with the diff locked, 100% of torque would be going to the front wheels. Same is true if the rears were on tarmac and the front was in the air, 100% of torque would go to the rear. Torque has to do with traction not wheel spin.

Same scenario, open diff. If the center diff were open in the above two scenarios, the car wouldn't move at all because the maximum amount of torque available in an open diff situation is determined by the end with the LEAST amount of grip. Whichever end is in the air has zero torque so yo aren't going anywhere anytime soon.

 

I know the Evo has a vicious type of differential, 3 LSD total but I noticed the IX doesn't have:

1. Traction Control
2. Vehicle stability Control


Does the Evo's ACD equates all those 2 above or is it better than having those 2?

 

Typically traction control and vehicle stability control mechanisms are not performance oriented. They are "safety" systems, not performance enhancers. The ACD gives you maximum performance given different traction situations. There is a distinct difference. The Evo isn't a BMW.

 

So then saying that the ACD control button has no effect on the torque split is untrue. ACD has full control of torque split, all the way from 0%(open diff) to 100%(locked diff). What it does not have control over is which axle has the most availble grip. Nothing the ACD can do can put more torque to wheels that are lightly loaded or on slippery ground (or in the air). It makes me laugh to see how aggressive people on this forum get while propagating misinformation.

 

I would read "full control" as meaning it sends exactly the amount of torque it wants to whatever wheel it wants, which isn't the case. The diff itself has a 50/50 torque split. That can't be changed per say.This applies when the clutches are disengaged AND after the point at which clutches start to slip. Once the clutches start to slip the excess torque goes through the 50/50 scenario. The amount of torque split up to the slippage point is determined by wheel grip. When you start applying the clutch packs with more and more force, it starts acting less like a differential and more like a locked axle. With a locked axle (pretend we welded the differential so it just locks the front and rear axles together) available torque between front and back is a function of available grip.

 

I think we're saying the same thing, perhaps it's just a difference in nomenclature. I used torque split to describe the torque difference that is able to be sustained between axles not the actual torque output from each axle.
ACD "off" and the output torques are equal, aka 0% torque difference, aka 50/50 input torque division. As the ACD increases clutch pressure the maximum sustainable torque difference increases, hopefully to 100%, and if one of the axles has less available grip the torque distribution will change to match that all the way to 100/0 (or 0/100). I do agree that the ACD can not send torque where ever it wants, so maybe "full control" isn't the best way to describe it. But the ACD does have some control over the torque distribution, if only when presented with unequal maximum traction situations.

 

http://www.gems.co.uk/downloads/manu...or%20V1.02.pdf

Interesting read. Explains alot about how the electronics are actually working.