In the 997 series the 4.0 liter engine was reserved for the (highly popular) GT3 RS 4.0. The 991 Series GT3 was powered by a 3.8 liter engine but that seems to change in the GT3 MkII.
If we believe the rumors the GT3 MkII (991.2 GT3) will receive the 4.0 liter engine. The car will make its debut in March, at the Geneva International Motor Show. This will increase the overall performance of the car and we've heard that the engine will produce 500 HP. But that remains to be seen, since it is somewhat odd that the GT3 MkII will have the same amount of horse power as the GT3 RS MkI. The biggest upgrade of the 991.2 GT3 will be the new manual transmission. The PDK will still be available.
