Best differential on a wet track?

And thinking about this a little bit while working, the negative torque thing is probably why my RX-7 (clutch diff tight enough that I couldn't tell the difference between it and welded) leaps to the inside of a corner when on the power. The inside tire gets overloaded so much that it isn't actually transmitting any power, so all accelerative forces happen on the outside. ZWOOP nose goes to the inside like it caught an arresting hook.

And from watching Evan's autocross video, the Miata rear suspension has a lot of toe-in under compression, which probably is combating that effect (his diff is tight enough to chatter on surface streets) but at the same time the handling spooks me, probably because the two effects don't linearly cancel each other out. I wonder if adding sway bars would make the handling more predictable...

Our OS Giken Super Lock in regards to how it works is very different than your typical clutch type LSD. Our unit is a negative preload design. This allows control of when 100% lockup occurs. With most clutch type LSD's you have to lower total lock (deactivate) or experiment with different fluids to allow the differential to open up and allow for better turn in. Because of this, those differentials are never 100% locked. This is commonly heard when tuners reduce their LSD lock to 80%, 66%, etc...

With a negative preload design, our units allow to be open during free roll (turn-in) and delay lock based on expected power delivery. All doing this while retaining 100% lock. We do not deactivate clutch plates as a tuning strategy. This also allows for smooth progressive locking during power delivery. Under wet conditions, progressive lockup is highly desirable and gives the driver more confidence in power delivery under low grip conditions.

Now the amount of lock timing greatly depends on how much power you make and how it is being generated. For relatively stock power, our units off the shelf are generally good to go. If you make a lot of power (ie. Street Modified), the differential will need to be delayed/slowed down to accommodate. If you are in Street Prepared, typically lightweight clutches/flywheels require the unit to be quicker as there is less stored energy in the drivetrain. Road Race applications are not as temperamental but still benefit from tuning as the corners are often long and slow in differential activity in comparison to autocross. The pressure ring in our units rely on torque to split apart and fight against the negative preload. In any circumstance, we at OS Giken USA can accommodate your tuning needs. If you have any questions, feel free to email me at J.Lugod@osgiken.net

Thanks for the input Jon!

OSG_Jon wrote: If you make a lot of power (ie. Street Modified), the differential will need to be delayed/slowed down to accommodate.

Low blocking factor? Or did you mean something different? Feel free to use technical terms, I'll (we'll) learn more that way.

OSG_Jon wrote: If you are in Street Prepared, typically lightweight clutches/flywheels require the unit to be quicker as there is less stored energy in the drivetrain.

Does that mean if I have a lightened flywheel, the BF of the diff has to be quickened? If so, can you shed more light on why that is? It makes sense since all the quick revving cars, like the LFA and the CGT, are a handful.

OSG_Jon wrote:...We do not deactivate clutch plates as a tuning strategy. This also allows for smooth progressive locking during power delivery. Under wet conditions, progressive lockup is highly desirable...

Just for comparison's sake, ATBs claim smooth power transitions as well. What tangible advantages does an OS Giken diff have over a "loaded" ATB in the wet? Let's ignore the obvious advantage that an OSG diff doesn't need both driven wheels on the ground if PTW ratio is high enough - this (PTW ratio part) wasn't obvious to me before Keith pointed it out. :-)

Thank you Jon, and everyone else, for your valuable input.

Hay GRM Staff. You need to get this guy to put this on paper and may be ask a couple more questions. Ok may be a dozen more questions. Also get one of your GRM Miata's and do some real world GRM testing. (like your tire tests that are always great)

I would love to see some articles on this as well.

Jon and I just recorded a podcast yesterday :)

What about us old folk that don't know what a pod cast is.

Yes, I did do a PodCast with J.G last Friday. I apologize ahead of time if my responses are not clear. I am much better at explaining things on paper than over the phone. If you have any questions feel free to respond to this thread or shoot me an email.