So 3 new liveries as well as more power. See here:
"Porsche will move up to the eight megajoule hybrid sub-class for its assault on this year's World Endurance Championship with its 919 Hybrid LMP1 racer.
The German manufacturer has achieved the move from the 6MJ division with the all-new 2015 919 using the same concept of energy-retrieval systems – front-axle kinetic and exhaust gas recuperation – and battery storage system as its predecessor."