With an output of 400HP the Alpina B3S is an Alpina in dire need of traction and grip courtesy of a Wavetrac ATB LSD!
Based on the 335i the B3S boasts a tuned version of the N54 twin turbo, pushing power up to 400HP. This sounds great on paper but with an open differential the one wheel peel struggle is real with this Alpina.
The Wavetrac ATB LSD for the Alpina B3S dramatically improves traction and grip, and through its patent protected design also offers dramatic improvements verses Quaife and Quaife like differentials currently on the market.
So how does the Wavetrac benefit over an open differential?
Standard, open differentials have a bias ratio of 1:1. They can only apply as much drive torque as there is available traction at one wheel. When one wheel loses grip, the total available drive is lost as well (at a 1:1 ratio). All your power goes out the slipping wheel – along the path of least resistance.
Torque biasing differentials offer increased bias ratios over open differentials. For example, if a diff has a bias ratio of 2.5:1, then it can apply drive torque to the wheel with the most traction (gripping wheel) at 2.5 times the traction limit of the wheel with the least traction (slipping wheel). This is a significant improvement over an open diff most of the time.
Why is the Wavetrac ATB LSD better?
The problem with all other ATB LSDs on the market is that when one tire has little to no grip (wheel spinning, suspension unloading under corner, bumpy roads), the other wheel gets ZERO DRIVE, because (basic math here): 2.5 x 0 = 0.
Lift a wheel (or substantially unload a wheel) and you get zero axle-load on that side – that means that during the time the wheel is unloaded, the typical diff will NOT power the wheel that’s still on the ground. No matter how high the bias ratio, you get no power to the ground.
The Wavetrac is different:
The innovative, patented, Wavetrac® device in the center of the diff responds during these exact conditions when zero or near-zero axle-load occurs. At or near zero axle-load, the axles (and therefore each side gear in the diff) start to turn at different speeds.
This speed differential causes the Wavetrac® device to step into action:
Precisely engineered wave profiles are placed on one side gear and its mating preload hub. As the two side gears rotate relative to each other, each wave surface climbs the other, causing them to move apart.
Very quickly, this creates enough internal load within the Wavetrac® to STOP the zero axle-load condition.
The zero axle-load condition is halted, and the drive torque is applied to the wheel on the ground (the gripping wheel) keeping the power down.
Some gear differentials rely solely on preload springs to combat loss of drive. The drawback is that you can’t add enough preload to prevent loss of drive without creating tremendous handling and wear problems at the same time. So, to avoid these problems, the preload from ordinary spring packs must be reduced to a level that renders them ineffective at preventing loss of drive. The Wavetrac® is the only differential that can automatically add more load internally when it’s required.
What this means for this Alpina driver is that power is delivered to the gripping wheels for more time and in a more constant manner making his Alpina faster and improving stability.