Recently done a lot of reading on this myself, here is what I understand of it.
There are 2 types helical or clutch/plate type.
The helical will be amazing in the bends and pull you right round the corner but under hard acceleration in a straight line it will cause you to move across the road from side to side ALOT and will do it more so the more power you are putting down.
a brief explanation of how a helical works here;
http://www.toyotagtturbo.com/forums/showthread.php?t=26504&highlight=lsd+diff
the main helical types used in starlets are the Quaiffe and the TRD although the helical TRD LSD is now discontinued.
A helical requires very little maintenance hence the quaiffe lifetime gaurantee.
The helical would probably be best for track use.
The helical sends the power to he wheel of list resistance(I think) which means when going round a corner for instance it will transfer the torque to the outside wheel, this can cause problems however when driving on an uneven surface for instance(country roads)
The three makers of plate diffs for ep's are KAAZ, TRD(mechanical and still in production) and cusco
A plate type diff comes in 3 forms, 1 way, 1.5way and 2 way.
A one way locks the wheels when under acceleration only.
A two way equally locks under acceleration and braking (can cause understeer when braking etc)
A 1.5 way is the best of best worlds as far as I understand it as it gives full lock under acceleration and partial lock under braking which helps to minimise any understeer.
An explanation of a plate type here;
http://www.toyotagtturbo.com/forums/showthread.php?t=26496&highlight=lsd+diff
Plate type's are notorious for lots of knocking whie slowly turning corners, the cusco one moreso than the KAAZ and TRD diffs. The knocking can be minimised if not completly got rid of by;
1. Using the right sort of oil with the correct friction modifiers
2. Breaking the LSD in correctly on first use.
the Plate type diffs require regular oil changes to prolong their life.
http://www.bodykitsonline.co.uk/blog/?p=211
I will be purchasing one of the 1.5way KAAZ LSDs as from what I have read they are the best for road use. I'll also be going for one of them so that when I am overtaking someone in a narrow road I don't want to be getting pulled all over the road and find any potholes etc that could contribute to an accident on the road, that isn't really an issue for when you are on track.
the cheapest place i have found a new KAAZ diff from is;
http://www.limited-slip.com/acatalog/toyotastarlet.html
I'm not sure the cheapest place to get a quaiffe.
I would also buy new as you don't know how shagged a used one is and could end up costing you more in the long run.
Rich
