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When I go to “race start”, I’ll launch hard but then get quickly shut down when the “4Matic Unavailable” message pops up. The car basically falls flat on its face for a few seconds, catches itself and then will take off again (me not letting off full throttle).

I’ve tried turning traction control to sport mode and also turning it completely off and it still does it. Same if I manually shift with paddles or let the car shift itself. Sort of makes the race start completely useless.

I will note I’ve got quite a handful of bolt ons and a tune, so my power levels are a bit over stock and I imagine I’m spinning quite a bit when doing a “race start”

Has anyone ever solved this issue? Or potentially had their tuner eliminate this shut down feature, if possible?
 

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Yeah, still on the stock tires. I know I'm going to need something more sticky... and wider.
I myself had 4Matic unavailable brutal bad (bouncing off rev limiter and doing front wheel drive burnouts - even from light race mode (2500 rpm and no exhaust popping) just brake hard and mash pedal. (no paddles)

Traction - As far as I am aware, is the only way to remove the 4Matic unavailable issue.
How? sticky and/or wider tires.

Understanding the issue:
The root cause comes down to the (cough cough - $h it ) design of 4Matic and the use of clutches in the rear. With enough power, the clutches quickly (and the PCM will preemptively disengages these clutches - and notifies you with a '4matic unavailable) during a quick ramp up of temperature as these clutches encounter friction. Friction is caused by loss of traction between driver/ passenger in rear and/or front / rear differences...
In my mind, this is the moment when I want AWD the MOST! yet it becomes a FWD burnout fest...

I managed to stuff 265 35 20s Advan apex v601s on 20x9 wheels. (ET41) all around - been meaning to post about this but been so darn busy.
One could easily go with 10 or even 10.5 wheels in the rear with the proper offset and have staggered with larger in rear.
 

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Yeah, I've had the same thing happen. I believe it's from the wheel spin, since that's the only time I've had it happen. The stock tires are pretty horrible unless they are plenty warmed up, and the pavement is smooth and hot.

Good to know on the fitment of wider rims GLAmapper! I've got my eye on some 19" upgrade rims to fit the specific tire I want.
 

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When I go to “race start”, I’ll launch hard but then get quickly shut down when the “4Matic Unavailable” message pops up. The car basically falls flat on its face for a few seconds, catches itself and then will take off again (me not letting off full throttle).

I’ve tried turning traction control to sport mode and also turning it completely off and it still does it. Same if I manually shift with paddles or let the car shift itself. Sort of makes the race start completely useless.

I will note I’ve got quite a handful of bolt ons and a tune, so my power levels are a bit over stock and I imagine I’m spinning quite a bit when doing a “race start”

Has anyone ever solved this issue? Or potentially had their tuner eliminate this shut down feature, if possible?
perhaps the clutch slippage rate is exceeding the value the TCU allows. Did your tuner increase the clamping pressure to account for the increase in commanded torque ?
 
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