Very respectable times. Good job!

Thanks!

Tire plans are coming together.

I went ahead and ordered some of those discontinued Conti/Hoosier wet race tires, in 265/645R18 (Hoosier Racing Tire -- Tires Designed For Champions -> Road Racing -> Discontinued -> bottom of page - $100/tire!).

Ordering another set of 18x10+34 Forgestars to stick them on, too. It'll probably be ~5 weeks to get the wheels in, at which point I'll finally be able to swap between decent dry+wet options in the paddock. 18x10 may or may not be the most-optimal rim size for those wets, but it'll be close enough to work, and in the long term I like the idea of having all my rims the same size and then just keeping an eye out for matching tire deals.

On the dry side, I'm figuring when this current set of RS3's run out of steam (probably mid-Summer?), I'll be ready to try some dry slicks too. My plan there is to pick up random brands of cheap scrubs, it shouldn't be hard to find them in 18x10.

Also, the next long-overdue equipment upgrade on my list is a 1.5-way clutched rear diff. Any recommendations? I don't want to spend forever on setup and go customizing the internals, I just want a reliable diff I can shove in there and change fluid regularly and it works better than the VLSD (well, by now I'm just using an open diff, my VLSD is shot). I'll probably have a local shop that specializes in diff/trans work do the install, I don't have the expertise or patience to sit around trying to shim gears together perfectly (I've done it before on an old truck - it sucked and I doubt we really got it perfect, but it kinda didn't matter on that vehicle!).

My shortlist from remembering older threads: Cabonetics, OS Giken, Nismo.

Look up Cusco LSD
Ive read a lot of good comment about them also they are very popular on the my350z dot com. They arent priced as high as the OS giken and pretty much as tuneable as them plus Cusco wont say no to help you with some tuning info/parts if you ever go that route later on.

I've heard very good things about the NISMO GT Pro. That's what I've got to put in my SpecZ car

Differentials are an entire world of their own. I feel like I could spend 5 years researching diffs and still not make a fully-informed decision :p

Cusco: MZ-vs-RS-vs-Hybrid? And given it's easy to customize before I put it in for the first time, any reason to re-arrange the disks for less-than-full lockup, etc?
OS Giken: reputable, pricey, solid option, not much else to say?
Nismo: GT Pro - Even more expensive than OSG, somehow? Their marketing materials do sound nice, but I don't know if it's that nice.

I had decided a while back (just based on internet research) to skip over the Quaife just because the one-wheel-lift thing seems shitty, and as I get further in my suspension setup, that scenario gets more and more likely. But now I've noticed that there's another torsen type called WaveTrac that claims to be very similar but eliminates the unloaded-wheel problem. That makes me wonder if I should give it a shot. The huge upside of the torsen-style ones is they're basically maintenance-free. Just change fluid once in a while and ignore it. If the WaveTrac really gets rid of the Quaife's main negative point, how much is all that 1.5-way-clutched maintenance worth to me? Does the 1.5-way really feel/drive that much better than a torsen?

About the only thing another evening of research has sorted out for me is I probably don't want any of the Carbon options (from Nismo or Carbonetics). Once you get through all the marketing BS, the bottom line is all the Carbon surfaces do is reduce noise and maybe modify fluid/clutch life, but the metal discs perform better.

Fingers crossed, I still hope with my diff cooler that the OEM can be used fairly well. We know the diff fluid reaches 300* + on the track. That can't be good for the silicone filled VLSD. But if you could keep that fluid always cooler, the silicone might do its job as well as it does on say lap one...all I know is just being on the highway my fluid hits 204* after 45 min. Within 10 seconds the temp drops 40* when I hit the switch. Highest I've had it with the pump on was like 164* I think. Only time will tell now.

Like you. Everytime I do reseach on diffs. I end up with a headache.

In my opinion depending what you want to do if its about track stuff I strongly suggest a clutch lsd in general. As far as longevity with Cusco from what ive seen in the pass on my350z dot com . There has been a lot of them running it for years including drift . I havent seen anybody as far I can tell having to rebuilt it... what they endup doing is changing the locking ratio from 60 to 80 then 100.... dont forget also on the cusco RS you can switch it to a 2way if you want. I cant say for the other one..

The nismos lsd was also quite popular in the pass because it use to be very cheap 800-900$ the only issue some guys were complaining about the noise of it more than other clutch lsd...

I can say for the os giken. They are a brand name and all I know is some guys had problem getting info and parts to tune the lsd.

This is why I went to a cusco rs .. 2 of my friend is running it . One use to have a kaaz which is another clutch lsd in similar price range as the cusco .. unless it changed in the last year or two.

From what I've gathered:

OS Giken - Smooth, Reliable and most expensive
Nismo/Cusco - Practically the same. Might want use WPC treatment on clutch packs. Parking lot speed/turns will make the car sound broken
Quaife/WaveTrac/Torsen - Might boil fluid, a little cheaper than the clutch types, low maintenance, quiet/unnoticeable.

From speaking with you, you said you wanted to remove the rear sway bar, and that would help with getting the rear wheel to droop more and stay on the ground.

The purple Z had a Cusco, dunno if you heard it or not.

Don't care about noise, since this car isn't driven on the street at all anymore.

Well, either way I'll probably do a diff cooler, though it may come later than the diff install itself. That aside, though: if we ignore the wheel droop issue, does the torsen-style action actually perform/feel better or worse on-track than a 1.5-way clutched when cornering hard? I know that's a somewhat-subjective question, but it seems to be the key question in deciding whether the maintenance/cost/complexity of the 1.5-way is worth it, and nobody ever answers it in a straightforward manner. I'm willing to give WaveTrac the benefit of the doubt on killing the wheel droop issue, their solution sounds reasonable.

Yeah, I guess that's true as well. Although, on the other hand, in general with my JRZ's there's very little available droop in the rear to begin with. When I put the car on the lift the fronts droop as expected, but the rears droop very little, relatively speaking. I'm guessing if I up the spring rates a bit when I remove that bar, that will help a little as well.

This mean using the Z on the track only , then a clutch LSD is the only way to go !
If it was 50//50 street /track then maybe yeah that wavetrack could fine good enough

don't worry on the maintenance cost on the Cusco,,, like I said I haven't seen/heard anyone yet having to rebuilt one.

This has been a really informative thread on the subject (well, after you filter out the stupid posts): Quaife vs Wavetrac vs OS Giken

How convenient that this post appeared today!
MY350Z.COM Forums - View Single Post - New NASA Class for 2012: Spec Z

Track cars still have to maneuver around the grid or your driveway etc! Still worth noting minor inconveniences that will always exist.