[Snowblind]

What's needed for the M6 to beat the A8 ?

Great question; I think what you are trying to ascertain is how to equal the two instead, right?? They both have the same motor with the same output.

The M6 has 2 small advantages over the A8 going for it, a weight savings of about 40 lbs? and no slippage of a torque converter.

The disadvantages are also 2 things; humans can not shift as fast as a computer and the the gearing is not optimal.

Equipping the M6 car with a 4:30 differential will give you an effective first gear ratio close to the A8 to close the 60' gap and it will also let you run it out to 121@6500 in 4th gear (on stock tires).