He said 0-60 mph acceleration would improve by 0.1 second—meaning a 3.1-second time—thanks to changes to the inverter algorithm.
In a later tweet, Musk also said "P85 acceleration will also improve, but not quite as much." The rear-wheel-drive P85 was Tesla's top performer before the P85D showed up, and has since been discontinued.
The P85D achieves its quickness with a dual-motor all-wheel-drive system good for 691 horsepower. An independent dyno test recently confirmed 864 pound-feet of torque as well, and thanks to the instantaneous response of the electric motors, that's available at the first twitch of the right pedal.
That's allowed the P85D to face off against a few more traditional performance cars, including a Ferrari 458 Italia and Lamborghini Aventador. The videos of it drag racing those shoutier machines are becoming the Internet cat meme of the car world.
While its power output and acceleration are hard to beat, the P85D's top speed of 130 mph is relatively modest compared to other super sedans like the Dodge Charger SRT Hellcat and the upcoming 2016 Cadillac CTS-V. Tesla plans to raise that top speed to 155 mph though, matching many a German sports sedan.
With these updates, the Model S P85D should be an even more potent performance car than before. And thanks to its relatively silent electric powertrain, no one will ever hear it coming.