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i brought this up before about acd...

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Old Sep 9, 2005 | 01:16 PM
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From: north jersey (15 min from nyc)
i brought this up before about acd...

i brought this up before about the active center diff on the evo and im still wondering how it makes any sense. Okay, the acd on the evo transfers torque 2 ways, either 50:50, or 100:0 where all of it is in the front wheels , the sti's acd system transfers torque either 50:50 or 35:65, with more torque transfered to the rear,(if my official numbers are off, please correct me), having that said, how the hell does the evo outhandle the sti? i figure transfering the torque 100:0 would be a bad thing and have loads of torque steer, plus, the relative weights of both cars are about equal which rejects the theory that weight of the cars is the reason for better handling. I understand that the boxer engine is longitudinally mounted and horizontally imposed which allows them to transfer more torque to the rear whereas the evo cannot do this, i figure that the sti acd system is thus better, yet the sti understeers and the evo does not? Can anyone make any sense of this? I also understand that the steering wheel lock on the evo is 2.0 compared to like a 3.0 of the sti, do you guys think this is the sole reason why the evo outhandles the sti? Maybe if you modify the steering lock of the sti, it would outhandle the evo because the wheel would respond just as quickly, its acd seems at least on paper to be the more effective system?
Old Sep 9, 2005 | 01:20 PM
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uuum, im pretty sure that whatever the ACD setting is at, it is always 50:50, and then makes adjustments based on slip, sti's do not have and ACD, they Have a VCD
Old Sep 9, 2005 | 01:32 PM
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Yes, the Evo is always 50/50. ACD just changes when the diff locks.
Old Sep 9, 2005 | 01:35 PM
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Originally Posted by Warrtalon
Yes, the Evo is always 50/50. ACD just changes when the diff locks.
are you guys sure? i asked the mitsu tech guys and read it in an article as well, they said that the car basically has 2 modes, 100:0 and 50:50
Old Sep 9, 2005 | 01:39 PM
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I've seen my friends car run 100:0 when he blow out the rear end
FYI i haven't met a tech worth listening to thus far
Old Sep 9, 2005 | 01:50 PM
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too lazy to search rite now, but on another thread there was a link to full explanation on some website. if anyone cares to dig that up.
it says something like this: evo is normally a 100:0 car (it started out as a FWD and later AWD was thrown in), but then the ACD will allow UP TO 50:50 and anything in between (65:35 on snow setting, or something like that).
what i don't get is this: the gearing in the center diff is what should determine the torque split, that's why STI's center diff is called DCCD-driver controlled center diff, which means that it prolly changes gearing from 50/50 to 35/65 and then the viscous coupling changes the actual locking point. if that's the case, shouldn't evo's ACD system have the gearing that determines the split (50/50 as warrtalon said) and then the computer determines the locking point?
then why did the article i read said it starts out as a 100:0? and do the 3 settings control the locking or the actual torque split(with different gearing), which is not the same thing. did i just confuse the bejesus out of everyone or what? lol
Old Sep 9, 2005 | 02:04 PM
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aaaaaaah, im gettin so confused, lol
Old Sep 9, 2005 | 02:06 PM
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....the Evo was never FWD....it was, and is always 50/50
Old Sep 9, 2005 | 02:11 PM
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i'm talking about BEFORE it was EVO and only a lancer, obviously EVO was never a FWD, but it's based off of lancer
edit:
anyway, what i'm trying to ask is: if ACD only controls the locking points, then what is this 75/25 and 65/35 torque splitting business for the snow and gravel settings? if u can only split torque by using different GEARING, then what do those numbers REALLY represent?

Last edited by JoizeeX; Sep 9, 2005 at 02:14 PM.
Old Sep 9, 2005 | 02:13 PM
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I want to learn more about the ACD on our cars too. Someone with knowledge please post in this thread.
Old Sep 9, 2005 | 03:44 PM
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On the STi its DCCD or Auto. In DCCD you adjust how you want the torque split. Between 50:50 - 35:65. Hence the "driver controlled center differential." In auto mode, the ecu constantly adjusts the split, several times per second, based on traction and driver input (steering and throttle). It is most effecient in auto mode because the computer adjusts the split in milliseconds to adapt for the most "safe" traction. It's very hard to get an STi to oversteer in auto mode. Understeer is considered safer to car makers. The STi doesnt handle as well as the EVo for various reasons. Two reasons are suspension and weight. The STi is heavier and the suspension is softer than the Evo's.

Last edited by AWDrift07; Sep 9, 2005 at 03:47 PM.
Old Sep 9, 2005 | 03:52 PM
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Originally Posted by JoizeeX
i'm talking about BEFORE it was EVO and only a lancer, obviously EVO was never a FWD, but it's based off of lancer
edit:
anyway, what i'm trying to ask is: if ACD only controls the locking points, then what is this 75/25 and 65/35 torque splitting business for the snow and gravel settings? if u can only split torque by using different GEARING, then what do those numbers REALLY represent?
ACD splits torque by varying the point at which the center diff locks.
Old Sep 9, 2005 | 03:53 PM
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The STI and EVo are almost if not identical in weight
Old Sep 9, 2005 | 03:59 PM
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the sti is 40lbs heavier. not significant but not identical. The Evo is also ~1inch wider and 3 inches longer. it also has better tires.
Old Sep 9, 2005 | 04:13 PM
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^ not enough difference in weight to be able to actually tell. Also, an extra 40 pounds isn't going to anything for understeer, the car just doesnt like to rotate like the evo.

There are 2 big reasons the EVO outhandles the STI stock.
1) tires are better
2) camber is more aggressive (really helps with understeer)

The sti also requires a different driving style you have to start turning the car while braking earlier to actually get the rear to slide enough not to understeer hardcore.

And for the record, subarus do have better AWD systems than the evo's.


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