Quote:
Originally Posted by kyoo
thanks for the quick and dirty's. when you say requires one wheel to spin to lock, is it by a percentage of speed differential, or literally as soon as the speed is different? the speeds between the two wheels would be different almost all the time, except in a perfectly flat straight line?
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The OEM unit does not lock as soon as there's any speed difference. You wouldn't want that. You want a diff to be open when you enter a turn. Otherwise you'll understeer into the turn because the rear wheels are spinning the same rate and want to go straight. There has to be a solid spike in spin rate of one wheel versus the other due to gas pedal input in a corner, then the unit senses it, then the unit applies locking. But it is certainly not instant. The charts from the 3 part writeup, show the OEM diffs behavior.
The OEM diff is a "safe" diff. It locks gradually---and only when there is a significant rate of spin difference. A fast locking diff like an OS Giken Superlock can send a car sideways much more easily. This is why they do not put fast locking mechanical diffs on street cars. Some guy with a lead foot on the streets in a corner will send that car sideways right away and traction control will struggle to intervene in time. In more recent cars with electronic diffs, like the F8x M3/4, you can keep the diff open on the street, and then when the car is churning out high performance, the diff can lock more quickly. Pretty cool.
Spend some time reading that writeup.