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      02-21-2013, 11:39 PM   #73
Lieutenant Colonel

Drives: E90 335I, E92 M3
Join Date: Feb 2012
Location: Midwest

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Originally Posted by Techevo View Post
It depends what you’re doing with the car. If it’s hardcore trackwork the OS Giken is far superior due to the high percentage lock-up available (ie better traction) and adjustability to let you change maximum lock-up and pre-load.
OS Giken is mainly used in FWD cars in Japan. Take a look at their website. Lock up is ok for FWD cars, but for RWD cars, you don't want lock up while you are in mid corner.

See 3:30 to 3:50

Originally Posted by Techevo View Post
A Quaife isn’t a 1 way, 1.5 way or 2 way diff. This classification isn’t used for a non locking torsen (TORque SENsing) helical diff. The Quaife still transfers torque under deceleration.

The OS Superlock will be available in 1, 1.5 or 2 way. 1.5 way is exactly what you want for a RWD track/race car. This means it has maximum lock-up on acceleration (% lock-up depending on plate config, ramp angle and oil used) and a smaller percentage lock-up on deceleration (off throttle and braking) This slight lock-up on decel helps keep the rear end stable. It is not ‘open’ when you let off the throttle!

A 2 way diff isn’t called as such because it works under zero load (nothing to do with it) it is because it has the same percentage lock-up under acceleration and deceleration, and only really to be fitted to a ‘drift’ car due to the oversteer characteristics it causes.
I stand partially corrected, as should you. For a 1, 1.5, or 2 way diff, the issue is behavior on Load, No load, and overrun situations. I confused overrun with zero, or no load. on overrun, such as suddenly lifting off throttle during corner entry a 1.5 way does have more limiting torque, but when you power out of the corner the 2 way has more limiting torque. As much limiting torque in reverse as it does in the forward direction. % lock up has nothing to do with this.

Originally Posted by Techevo View Post
Functionally, the full plated OS diff is the most efficient differential due to being able to create the highest percentage lock-up of all types.

Basically these are some guidelines for using the different diffs.

For a mainly road car, with occasional trackwork where the suspension droop is adequate to not cause a lifted wheel, the Quaife diff is preferable.

If there is any possibility of lifting a wheel a Wavetrac is preferential.

For maximum traction and lock-up and much better adjustability, but will require more maintenance and not fit and forget, the full plated diff such as the OS, is preferable.
Functionally the OS is the most complicated. % lock up has to be determined and set up before manufacture. In units where % lock up is adjustable post manufacturing, the process of changing lock up percentage is too complicated, and time consuming. Then again, there is the issue of lock up being undesirable in RWD cars, during cornering.

My summation is: Quaife for the streets, OS Giken for street/some track, Wavetrac for ALL driving situations.
E90 335I: FBO +wavetrac LSD
E92 M3: K&N, Rouge Engineering Pulleys, Macht Schnell Test Pipes, Evolve Tune, Pagid S, V1