I'm planning on getting a rear cusco 1.5way RS LSD later this year. I'm a little confused on how this is going to go in though. On the Evo VIII and IX, it was a straight swap when you got a TRE. I'm hoping someone's gone through it and can answer some questions for me:

For the X, does the cusco LSD go into the stock case?

How does that interface with the AYC?

And since this will be working with the AYC, how to bleed the controller? I've noticed two nipples but am not sure how to force the bleed.

 

My first reaction to this was: "given how the AYC works and given how a 1.5-way works, it seems impossible for a car to have both." I have no idea what the answer to your question is, but would love to know more about this combination. Wouldn't an activated AYC fight against the locking of a 1.5-way at corner exit?

 

I don't think it would fight against the main rear diff. Also, Ryan Gates and EvoDave run this.

 

Oh, after a few searches around (before posting the first time), I saw that several people who know what they're doing have done this. Now I'm trying to understand how it works.

My understanding of the AYC is this: when the S-AWC ECU detects, for example, a power-on left turn, it starts to lock the special shaft (that is geared to turn faster than the average of the two outputs) to the right output. The reason that the right rear is able to turn faster than the average is because the differential, itself, compensates by turning the left output slower. In a nutshell, the AYC works by bypassing the differential to some extent and connecting the prop shaft to the outside rear, and it gears this connection to rotate the outside rear faster than the average of all four wheels (assuming, for the moment, a locked center).

But if the actual rear diff is locking because you are powering out of the turn and the LSD on the rear diff is a modified clutch-pack (like a Cusco 1.5-way), then the LSD on the differential will fight the action of AYC. The AYC wants to rotate the outside rear faster than the inside rear using the differential, but the LSD wants to lock the rear diff.

It's the second part that makes me wonder how this all works together. Even if I assume that neither the AYC nor the Cusco is locking very hard, to the extent that both are locking, they would seem to be fighting each other since the AYC wants to rotate the two outputs at different speeds and the LSD (as always) wants to lock them together.

Can you help me to understand this?

 

I just reread the technical reports on both the old and new version of Mitsu's AYC. I'm back to my original impression: you cannot have a LSD on the rear diff if you have the old AYC (bevel-type) or the new S-AYC (planetary-type); they would "fight" each other.

So I did some more searching and found that people who have put a Cusco 1.5-way in the rear of an Evo X have also disabled or removed the AYC. See here, for example: http://www.***************/forums/ar...p/t-12938.html

edit: OK, so I can't post an external link. Sorry. But a search using google for "ryan gates evo x cusco differential" will locate the place where Ryan says the AYC in his car is inactive.

 

I ended up contacting AMS and they said that it does just replace the rear diff w/o affecting the AYC.

Also, I couldn't find anything about inactive, but I do remember reading about Ryan saying that the AYC was no longer doing its job effectively after a certain power range.

 

Did AMS say anything about only using the RS version (i.e., the softer-locking version) of the 1.5-way? I've been going over this forwards and backwards, but I still can't see how both systems (the AYC and the LSD) could both work at the same time without one or both being incomplete.

 

You have to use the RS version as the MZ only comes in the version that doesn't work with the AYC. Also, got an email back from cusco confirming it's good to go.

As for the actual tech behind it, I'm not really sure.

 

OK, then I guess I understand. Even if the two devices are contradictory, with the LSD trying to equalize the speeds of the two outputs, while the AYV tries to make the outside output turn faster, as long as neither locks completely, they can be used together. It seems sub-optimal, but maybe I'm missing something.