I know that some AWD vehicles used the gear ratio of a planetary or other transfer gear combined with a gear type torque biasing diff that would allow a natural mechanical advantage to apply more of the torque to the front or rear axle. Why not apply this to a rear diff for circle track racing. the bias would put more torque on the more highly loaded right rear tire of course. I was thinking that the gears inside a Helical LSD could be arranged for the bias, or a reduction gear added to the right side output. Or, ideally, you could just replace the diff gears with a planetary set that has the left axle connected to the sun gear, the right axle on the planet carrier and the ring gear attached to the uh.. ring gear or diff case. You would have an open differential that is biased to the right side. If you can get the ratio right for the grip difference for a given lateral acceleration or corner speed and radius, and car geometry, you could have an open diff with equal or better traction coming out of a turn to a LSD. Of course once you start to straighten the wheel and side loading is decreased, the right rear wheel may spin before the left side when a lot of power is applied. This would probably only be an issue for very high powered cars, as most cars would have limited torque output at the higher speeds once you are coming out of the turn, and the available grip is higher since there is less lateral load on the tires. This also should give you a little bit of overall reduction in gear ratio when turning left, raising the engine rpm slightly for a given speed. It might free up a car that is bogging getting on the gas. If you were to turn right, the gear ratio would effectively increase. I suppose you could also get by some rules that require an open differential. You would still have an open diff, it would just have a different amount of reduction to each side.