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      08-14-2009, 02:21 PM   #10
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Drives: F80 YMB
Join Date: Jun 2005
Location: VBeach VA

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Originally Posted by scheherazade View Post
If your car is before 08', then you don't have the e-diff program.

The E-diff program is active when stability/traction is off. It is designed to act as a simply LSD, which prevents runaway wheel spin.

No e-diff program means that with reaction/stability 100% off, there is no electronic assist to stop a free-spinning wheel.

Quaife only works when wheels have load. If you actually spin a wheel (0 traction on one side), it stops working.

If you had the e-diff software, then the brakes would catch the free spinning wheel, causing a load on that wheel. Which in turn would make the quaife re-engage and you'd be all-good.

This is why I went with Wavetrac... because I don't have the e-diff software (XI) and I want the diff to keep working when one or both wheels slip.

Not exactly. My apologies if what follows seems like a bit of a tirade but there has been a fair amount of misinformation posted regarding "e-diff" and model year differences.

All E9xs have some variant of "e-diff" = traction and stability control via braking and power reduction = DTC/DSC.

"e-diff" is a misnomer. The algorithms for DSC/DTC in later model years are a bit different than earlier models, but nothing very significant.

The effect of DSC/DTC on the actions of the Quaife QDF are complex. The QDF model does not result in completely free spinning of an unweighted wheel as some have suggested. There is always some tension that results in torque transfer.

Put simply, regardless of whether you have a 2007 or a 2009, installing a real LSD (Quaife, wavetrac, whatever) will have a big effect on traction and handling. I attach the Birds blurb. For an unbiased review of the results see
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File Type: pdf E9233928336.pdf (305.9 KB, 186 views)