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      10-03-2018, 09:03 AM   #304
dogbone
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Drives: '09 E90 M3 - IB
Join Date: Feb 2012
Location: 93 million miles from the Sun

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2009 BMW E92 M3  [0.00]
2009 BMW E90 M3  [0.00]
Quote:
Originally Posted by kyoo View Post
does anyone have any links on the oem rear differential, and how it works/is electronically controlled, with the various levels of traction control on/off?
I did a long three part write-up about the differentials and compared the OEM unit's performance to an OS Giken Superlock. It has tons of AIM Solo DL charts showing how the rear wheels spin in relation to each other at Buttonwillow Raceway. Start at post #173.

https://www.m3post.com/forums/showth...1158445&page=8

It's really really long, but I think it might have something in there for you.

But a couple quick answers to your questions:

-the E9x M3 diff is not electronically controlled. It's a speed sensing unit and requires one wheel to spin up for it to lock.
-traction control does not prevent the rear wheels from spinning at different speed. It still allows that to happen. Otherwise, there's no way for the unit to lock. Most of traction control is done by cutting engine power, and individually engaging the front brakes as needed.

I also did a write-up showing traction control behavior. Many people think traction control uses the rear brakes mostly. This is incorrect. The AIM Solo DL can show how all four calipers activate individually. I posted some fairly quick laps from several tracks showing traction control engaging the front brakes almost 100% of the time. You can check that out here:

https://www.m3post.com/forums/showpo...&postcount=747
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