How does Porsche consistently improve its NA flat-six? Clever engineering
For all the talk we hear about EVs, internal combustion technology is seriously advanced. Engines can make huge power without the compromises once necessary to guarantee efficiency and reliability. And when it comes to naturally-aspirated engine bliss, the 2022 Porsche 911 GT3 is a shining example.
Purists rejoiced when the announcement came down that Porsche would once again forgo a turbocharger for the driver-focused GT3, equipping the hot-rod 911 with a 500-horsepower, 4.0-liter flat-six mated to a six-speed manual. How Porsche pulled off that power figure is worthy of discussion, and Jason Fenske of Engineering Explained breaks it down.
It used to be a marvel for an engine to produce 100 horsepower per liter, but the GT3’s six-cylinder mill cranks out 125 hp per liter. Some serious engineering is required to get the necessary air and fuel into the combustion chamber to make a number like that and to pull it off the team at Porsche relied on clever design rather than a turbocharger. The opening and closing of the intake valve creates pressure waves that reflect around in the intake manifold. Tuning the shape of the intake manifold allows the engineers to use those pressure waves to cram in more air with each opening of the intake valve.
As Fenske points out, utilizing that pulse of air provides the new GT3 nearly the same torque per liter as the twin-turbocharged V-12 from a Rolls Royce Ghost. The four-liter six is also almost identical to the V-12 when comparing the brake mean effective pressure (BMEP), which describes the average amount of force on the piston as the engine cycles.
Of course, there is a catch to tuning the intake manifold in this way. Given a static intake, conditions can only be perfect at one particular RPM. Le Mans race cars like the Mazda 767B used variable-length intake runners with solenoids to adjust and tune the intake on the fly, but a high-maintenance approach like this is impractical for a road car. Porsche came up with a simpler solution. By gating the intake manifold with multiple valves, the various compartments can be opened and closed based on engine RPM. With this setup the ECU can easily tune the intake on the fly, but I would bet that throttle body cleaner will be a major service line item: six individual throttle bodies, along with the multiple valves for the active airbox, is a complex arrangement.
Overall, the new GT3 is a feat of engineering that impresses on a multitude of levels. Some even say it is the most important modern Porsche in the lineup. One thing we know for sure is we’re happy this 500-hp work of art is in a thrilling car you’ll be able to see on the road very soon.
