Same opinion. Mine was preloaded to 110ft.lbs initially, no idea what it dropped off to after it "broke in". The car would NOT turn in, even with the RSB attached, and then it would spin the inside rear HORRIBLY on corner exit. This was all at 200whp. Less/more preload would have exasperated one problem or the other - having both problems at the same time quickly convinced me that the Rx7 diff is the wrong way to go. Kotomile has my Rx7 diff now, even despite my warnings about how shitty it was. He said he wanted something stronger than the Torsen, and the Rx7 diff is definitely that. I swapped back to a Torsen and all of those problems went away - nice predictable turn-in, nice smooth power application on exit.

At 270, the Torsen starts to get a little crappy, and it's really holding me back now that I'm at 350. I have the power to spin the inside rear even if it's not completely unloaded, and once it begins to spin I have to pedal it until everything hooks back up again. It's really bad at some tracks and not too bad at others. As Bob said, it's really bad when you are coping with bumps or pavement undulations, like exiting the Omega at WSIR or turn 11 at Thunderhill. For instance, Laguna Seca doesn't cause an issue, except in turn 11, since the track falls away from the apex to the trackout point. If I get into the throttle when I want to, the IR spins and I have to pedal it.

I borrowed an OSG from Emilio for RTA last year and it's absolutely magical. The car turns in properly, and it just hooks up and goes on exit. Even if you have a little slip angle on the way out, it will just haze both rear tires without even putting up a fight.

As far as RSB vs. no RSB, it helps a little on exit but my car needs the RSB to be balanced everywhere else - if I can't get the car rotated correctly there's no hope of getting away from the apex with any sort of drive.

Is a preloaded torsen possible? Is it possible to squeeze a small self-contained viscous or clutch unit inside the torsen and attach it at the center of the output gears? How much room is in there? It wouldn't have to provide for the full strength of limited slip, it would only be preloading the torsen unit. If it put 50 ft-lbs of preload on the torsen, then the torsen would treat a wheel in the air as having (0+wheel inertia+50 ft-lbs) of torque, and would use that to apply torque to the grounded wheel.

I wish I could tell ya how amazing it was to swap from a Torsen to an OSG.... but I went straight from a viscous to OSG - now THAT was a change. I'm only at 225 too, but I'll take Sav's word that I'll be glad I've got the OSG once I put in my built 1.8 at the end of the season. It's awesome fun coming out of #5 and #8 at Barber, very predictable.

I was searching for a diff after driving Johnwag's car with a Cusco. However since putting the AST dampers in I don't feel the need to buy a diff. I was getting on the gas just as soon as I did in John's 130whp car with no-more inside wheel spin when sucking-up the curbs.

It's my understanding that when you unload the inside wheel on a Torsen, it turns-into an open-diff. If the high-speed valving is right, the inside wheel stays on the pavement and never unloads the inside wheel, it won't spin.

I bet a real diff in my car would be epic.

That is what a Torsen R is. I believe they come stock on S2000's?
I blew up my stock '99 Torsen autocrossing it. Lifted the inside rear, got on the throttle, it spun up the wheel, and ate some teeth off of the worm gears when it landed. Switched to a Cusco Type RS. Turn-in suffered compared to the torsen, but exiting the turns is much better.

Quick note because I didn't know: Per Torsen's website, the Type A (Torsen T-1)differential is superior to the Type B (Torsen T-2) differential for getting power to the wheel with traction. IIRC, the Type A Torsens were found on 94-95 cars, and the Type B Torsens were equipped on 96+ Cars.

The Racemaster (Torsen T-2R) was designed to provide the higher bias found in the type A Invex gears while using the newer T-2 Equvex gear style.

Food for thought.

at 300ish whp, the torsen started acting up, at 400whp, it is useless, feels like an open diff. The osg is without doubt the best diff i have tried ever :) no chatter og clunking when driving on the streets, cant really tell there is a racing type diff in the car as it feels more like a stock mazda diff. Compared to lets say kaaz diffs, well.. it cant really be compared(kaaz is klunky and terrible all the time).
when accelerating, the car would wander from side to side as the torsen struggled to find grip all the way past 80-90mph. with the osg, it just feels planted, much more stable..
Turn in is also great. we are building another 400whp miata now. and were putting a osg unit in it from the start. no point even running the car with the torsen. Better of selling it before it breaks(like mine did)

I've been thinking about the Quaife LSD. Does anyone have experiences on the Quaife?
http://www.horsepowerfreaks.com/part...ip_A.T.B/16679
The price of the Quaife LSD is about 800 euros in Europe and the Os Giken LSD is about 1500 euros.

Was this on a stock Torsen(R) unit, or were you using an aftermarket gear bias differential (such as the Kaaz)?

It's strange to think that you would be breaking individual tires loose - I would expect that the coefficient of static friction between a tire/asphault is less than 2 1/2 times the coefficient of kinetic friction - especially a sticky race tire which tends to have a significantly less frightening transistion from "stick" to "slide"

I could see it rolling out of a corner

kaaz is not a gear bias diff, it's all clutch.

and it's not all that terrible on a street car. I've had mine a long time and it's only clunky if you're trying to zip through U turns. not anywhere else.

the biggest issue I have with it is how it straightens the car out when you get on the gas in turns.

On diffs…note that it can be misleading to just swap and choose the "best". For the best results given very different diffs, you should also tune your car setup and driving strategy a bit. Some that "promote" understeer will perform better if other things are also changed to accommodate that tendency. They can also affect brake setup as the nature of any rear lockup characteristics can become more or less pronounced. Which can be a big thing for those that like a lot of rear brake (retaining stability) as I do. On some cars I've setup, a diff swap could allow a few hundred more PSI at the prop valve's knee point. This stuff is all interrelated...

coming out of sharp, high grip 3rd gear corners on a track, using 225 R888 tires, it would spin the inside tire like posessed.. it simply was not able to transfer enough torque to the outside wheel to break it loose before the inside started spinning, atleast thats what it feels like. And then i had to get of the throttle a bit, find grip, and easy back on the throttle again, just like running a open diff :) This was when using the stock mazda torsen diff. When opening the diff to install the OSG unit, there was massive wear on the spider gears inside the diff, on the sides trying to transfer power to the outside wheel. This had happend in just a few months use (it did display the same issue from day one when running 400whp), and the unit had no problems at all when running lower whp settings. seems that there is a point where the stock torsen just is not up to the massive task it is being dealt.

i must sound like a OSG sales rep . but it absolutly transformed the car. :bigtu:

Seems like EVERYONE that's tried/owns an OSG diff sounds like a sales rep. Speaks volumes for how badass that diff is.

In case some missed the article…while the test used an S2000, the details are still interesting:

http://grassrootsmotorsports.com/articles/whats-diff/

Quaifes work similarly to a Torsen, get the inside tire light and it acts like an open diff.

Although…at least some Quaifes have a preload adjuster set via belleville washers…you have to open up the unit to get at them. I got a few Qs cheap after I helped them out with a lawsuit. Put one in an E30 M3 and another in a boosted Lotus Europa with nitrous antilag. I haven't compared a Q to an Giken but they were better than the usual BMW diff setup for racing. Those smear some understeer over the turn-in process whereas the Qs feel open at that time.

You'd think that, but two of the top CSP cars run a stock Torsen and RX7 diff. I know its not track, but diff problems seem to exaggerated in auto-x. I've driven two different cars with OS Gikens (a CSP Miata and X Prepared S2000) and I couldn't tell you there was difference between it and the Tomei diff I used in my old Corolla (AE86) in terms of performance. Maybe its just because I'm cheap, but I think I'll stick with a Tomei/Kaaz diff when the time comes.

Maybe those two CSP cars had the "whole package" tuned to work well together…quite often, LSD swaps need setup changes to max out potential.

Mine's only clunky when cold and quiets down after a couple of minutes driving. I do change the oil religiously though. Importing those cans cost me a fortune every time.

Speaking of Quaife, AWR and Flyin no longer carry the gearsets for the 5spds... new US distributor, bad sales, Quaife stop making them? I know it was crazy expensive - but the wideratio was temping with the 5spd. - not trying to change the topic, but I'll be needing something to handle 400rwhp (I'm serious) - been researching a various swaps - finding something with proper shifter location being a problem.

My OSG should not be a problem at that power level.