Sorka: I believe your statement above is _almost_ correct. It would be entirely correct if you swap "with the current pack" with "with the current fuse/contractor". The limiting factor for the current P85D is not Energy (ie pack size), but rather Power (how quickly the energy can be tapped). The current fuse/contactor on the current P85D can't handle anything beyond 1300 amps. They heat up and blow beyond that. The new fuse and contactor is an advanced design using better high temperature material, and can safely draw up it 1500 amps. With these new components in place the dual motors can safely draw higher power from the existing P85D pack, achieving ludicrous mode on 85kwh pack.
Per Elon's blog post "
The net result is that we can safely increase the max pack output from 1300 to 1500 Amps."
Here are my calculations:
For the current P85D
Fuse/Contactor Limit: 1,300 Amps
With a nominal operating pack voltage of 366v
Max Power = 1300x366 = 475.8KW
414kw is probably the result of a software safety limit to 87% of max fuse capacity. (475x87% = 414)
For the new P85D
Fuse/Contactor Limit: 1,500 Amps
With a nominal operating pack voltage of 366v
Max Power = 1500x366 = 549KW (736 hp)
87% of 549kw = 477.6 KW (640 hp)
So the fuse/contactor update for the P85D-Ludicrous allows Tesla to tap an additional 64 kW from the battery, leading to the 2.8s 0-60mph performance boost.
What is interesting to note is that Tesla still has some room for improvement. The maximum power rating for both motors combined on the P85D is 568 kW (or 762 HP), so if an even better fuse can be found, then additional power can be tapped leading to even better performance (assuming no issues with other factors such as traction, battery pack & wiring, etc)