I keep up with the E92 M3 crowd, and general consensus for the most part is the Giken OTS setup is great for track use. Some of that is because almost all owners don't really spend alot of resources to make much more power over stock, they focus on handling. Also, that car is tire limited really due to the body design. The exact opposite is true for the Z, most owners try to make considerably more power over stock, and the car can easily be over-"tired" due to the big body design. For the tire we can stuff under this car, it really needs to be making like 375 whp+. Not feasible for us NA track guys, unless you want to build a crazy 3.8L like the GT4 cars in Europe ran!

I've got a spare diff pumpkin just waiting to be rebuilt with a Giken for my M3, but just haven't gotten around to it. Knowing this though, I will certainly check into it before pulling the trigger for that car.

Being a Z34 owner with an OS Giken that I track often, and I think it's not biting hard enough....I think it has also to do with the fact that I've got a 4.08 FD, meaning the car is behaving as if it has a bit more power than stock.
That being said, the diff works well, it only locks up slower than I'd like if we're talking about a very sharp hairpin corner and I wanna drive through it like a maniac.

I had a call with a diff specialist from the Netherlands where I bought the OS Giken unit, and they said it's not a problem to tune it to bite earlier at all. You just need to swap out the negative preload springs for softer ones and that's it.....but to do that, you need to disassemble EVERYTHING.

Got my rebuilt Giken installed and tested, and it's a world of difference. Lock up is much harder, and no inside wheel spin. Car handless better than ever.

@ Prandelia - so what exactly did you do regarding the tune? How did you tune your diff?

I currently have my diff out and yesterday I went ahead and opened the OSG unit. My plan was to release some of the negative preload springs which would result in quicker lockup.
Stock I have 4 sets of 3 springs, each 28kg - one on either side. That totals 336kg of negative preload. I removed 1 from each side and I also exchanged 1 for a softer one, giving me just 184kg of negative preload. I'm now questioning whether I overdid it? I still didn't mount the differential back, so I'd like someone more experienced to chime in and give me their thoughts.
I am thinking about keeping stock springs, but just removing one per quarter, which would result in 224kg of negative preload, which might be ideal - but I'm not sure. I don't want it to behave exactly like a welded diff...but I do want quicker lockup.

Thoughts? Thanks!

I'll have to look it up. I just let the wizards at OSG tune it for me. I let them know I didn't necessarily want it to lock up much faster, but harder. It's progressive which is nice, didn't want to lose that, just need more overall lockup, but I'm sure it does so a little faster.