How Does Haldex Determine Where to Send Power With Traction Control Off?

[KevinM.]

So from my understanding, the S3 is pretty much a front wheel drive car, except when it determines it needs to send power to the rear due to a decrease in traction up front. So where is power sent with traction control off? If it is no longer componsating for loses in traction, how does it determine where to send power? Is it always in 50/50 with traction control off? Or is TC still actively increasing and decreasing torque sent to the front and back based on traction?

[LINDW4LL]

My understanding is that traction control does not determine where power is sent but simply cuts throttle/reduces engine power when excessive wheel slip is detected.

The Haldex system and wheel speed sensors should always be working to distribute the power in the most effective manner, regardless of whether traction control is enabled or disabled.

[HurrayFive]

Traction control is largely just a calculated brake assist at the wheel(s) losing traction, meaning the brakes are applied to help correct the wheel slip; in combination with stability control, which will also reduce throttle output in a effort to regain control/traction. The Haldex unit is working constantly regardless of what traction control is doing or what mode it's in, but the Haldex controller is also distributing power based on current wheel slip (or pre-sensing slip and distributing in certain conditions).

They are totally separate systems working in parallel, one doesn't control the other, but both work together to prevent loss of traction. The Haldex controller will continue to sense slip and distribute power across the front and rear even with traction and stability control completely disabled, the difference being there is now no additional assistance in the event of extreme slip. IE, complete loss of traction in all but a single wheel, or, sliding sideways with all four wheels spinning :)

[KevinM.]

Thanks Hurray, that was a perfect explanation. I thought they were one system, but I now understand that they are not.

[coolwater]

I was reading a thread where someone turned off traction completely, like to do a launch and it will turn back on after a certain speed. Like 60mph or something. Not sure if that's normal.

-cW

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[Antarius]

I was reading a thread where someone turned off traction completely, like to do a launch and it will turn back on after a certain speed. Like 60mph or something. Not sure if that's normal.

-cW

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It doesn't turn back on after a certain speed, but using cruise control will turn it back on.