If Autocar is correct, the next 911 will adopt a tri-turbo forced-induction system for its 3.8-liter flat-six, similar to what BMW’s introduced on its new M Series diesels. The net result will be more power, better fuel economy and improved throttle response.
Generally speaking, turbo systems are a compromise. Small turbos, while quick to spool up, generally provide low-end power only. Larger turbos can produce more top-end grunt, but usually exhibit turbo lag at lower engine speeds.
To get around this, Porsche has used a twin-turbo system on the 911 Turbo since the launch of the 993 variant in 1995. A small turbo provides off-the-line power, while a larger unit ensures that the 911 Turbo pulls hard at top-end, too.
As good as the system is, there’s room for improvement. Adding a third turbo will produce more linear power (especially at low-end), while reducing both emissions and overall fuel consumption. The trade off, of course, is increased complexity.
Since the next 911 Turbo is still in the development phase, details on power output and fuel economy are scarce. Rumor has it that the next 911 Turbo will be even more powerful than today's 530 horsepower Turbo S, and could pack as much as 550 horsepower in base trim.
Expect Porsche to use the tri-turbo system in the next 911 GT2 and 911 GT2 RS as well.