If I remember correctly the Evo uses four-channel ABS which means each wheel/brake sensor looks for lockup and the ABS system adjusts accordingly, so how would a front limited-slip differential interfere with this process? Technical wizards please chime in...

 

You are correct that a torque biasing differential is not a direct slip limiter. However, a torsen lsd is active in both braking and accelerating with different torque bias ratios. You don't have to believe me just check www.torsen.com or read through the patents. The abs imparts unequal torques on each axle as it tries to limit wheel lockup - any guesses what happens across the differential??

I only started posting to provide a data point - feel free to install one yourself and experiment.

 

are you braking with the clutch in, or out?

 

With the clutch engaged of course.

 

in this case it makes no sense why "modern abs" isn't smart enough... the mr and the 05s still have a front helical diff... acd does nothing but transfer torque from front to rear and vice versa... so how are they able to keep a helical diff in front if it is a matter of abs imparting different torques on each wheel or axel?

what makes even less sense is if you go to howstuffworks and look at how the locking torsen differential works you'll see that if something is applied to one wheel the diff has the ability to applie it to the other wheel magnified by the bias ratio amount. if one wheel spins the other wheel will also spin at the same speed in a locking diff and in a torsen diff an even greater amount of torque can be passed to the wheel with good traction (the non crazy spinning wheel).

so if you are coasting in a straight line... the torsen diff is not active... everything is going in the same direction. if you turn... the diff lets one wheel go faster than the other because all the wheels have traction... if you accelerate in turn, the diff will lock up and force both wheels to spin at the same speed allowing the inside wheel to spin up to the bias ratio amount times more fast than the outter wheel because the outer wheel has less traction and the inner wheel has more.

if you brake in a straight line nothing happens, if you brake in turn then nothing happens... if you brake and you engage your abs in turn then...

let's draw out this scenario since it is the most interesting. your inside wheel is moving the slowest so it will "lock first" assuming this type of action can actually engage the differential then your outside wheel will feel a negative torque of up to the bias ratio times without the brake caliper doing any work which may lock up your outside wheel causing you to.... understeer. ladies and gentlemen... this is given, everyone knows that ****in' abs makes you understeer... NO SURPRISE HERE! and in the case this happens your rear wheels liven up cuz yer center differential sees that they're getting more traction (right?).

the moral of this story...... don't ****in' engage abs in turn and if you hit a bad patch it'll only be on for a second making your already understeering *** underteer slightly more, that is... if indeed abs can activate the differential.

btw acd is a multiclutch electronic differential... it maintains a constant torque split between front and back and uses a computer to determine under what conditions how much torque is biased where.

for more on differentials http://autozine.kyul.net/technical_s...ion_4wd_21.htm

 

The '05 Evo does use a different ABS system, apparently it is smarter than the system on the '03 according to Mitsubishi.

 

Long story short, you can swap in the RS gearbox, but you better disable the ABS.

 

Not quite. ACD is a standard gear differential that uses hydraulic clutches to vary lockup. It does not vary torque split in a non-slip situation like the Porsche 959. Here's a link to the press kit on the Evo VII, when ACD was added:

http://www.mitsubishi-motors.co.jp/PDF-E/evo7.pdf

So basically the way ACD works is that it's a computer controlled LSD that can vary from being almost completely locked up to completely open. In Tarmac mode, it's the closest to being open, and in Snow, it's the closest to being completely locked. The torque split is a nominal 50/50 torque split, but in the event of slippage it can send almost 100% of the torque to the axle with grip, but this is not black magic. If you are in a situation where one axle has grip and the other has almost none, and you have a locked differential, 100% of the torque goes to the front axle since there is no friction in the back to allow you to apply torque to the back axle. ACD can't disconnect the rear axle, it can only put the center diff in a completely open state. DCCD on the Subaru does vary the torque split because the gear diff inside is biased 35/65. So as it locks up the diff, it approaches 50/50.

 

so the subaru has one more similar to the 959... i thot they were both the same... i only read up on the subaru dccd. documentation is hard to find from mitsu...where dccd is openly advertised on subarus site. in the case that all this matters a lot... can the 05 abs computer be swapped into the previous year models?

 

i figured out why the abs needs to be smarter. if you follow the situation i outlined above then your inner wheel is locked for a second which *might* cause the diff to lock your outter wheel with its torque biasing powerfulnesseses and standard abs would not know to release the inner wheel to get the outter wheel to start rolling again. but then again this type of abs would almost be like the braking assist system in autozine where the brakes help you turn better by biasing the inside brakes to cause oversteer.

i still don't see it as a big deal. even in the worst case when you hit a dirty patch and you lose traction and begin to understeer your abs would make you understeer more in that situation anyway, the added wheel lock is not a good thing and could cause you to end up in a ditch but... sigh... don't engage abs in turn... it's not a good thing... and we should all only be pushin' it so hard that we leave little margin for additional braking (to the point of locking) on roads we already know, i know all the dirty spots on my home course....

rre has co-oped with quaife to make this pretty lil 1g unit to slap on our gsrs... i trust it. i've only engaged abs once since i got the car... :\

 

makes little sense to me though...Evo's have ABS, and several of our customers have the Mitsu/Ralliart Helical front LSD we offer in their cars....no issues with brakes at all. Half the cars are JUST street cars, the other half are primarily track cars.

 

As another data point, a lot of DSMs have retrofitted quaife LSD front diffs into their cars and never have any issues with ABS. I don't see how the ABS can be much different between the cars.

 

alot of disagreements here...but basically the RS Tcase will fit and works right????

 

I can assure you it fits. I've had one FITTED to my car.