Porsche is playing back-and-forth with its naturally-aspirated 4.0-liter flat-six. The engine serves in the 991.2-series GT3 and GT3 RS, tuned to 394 horsepower and 520 hp respectively. Engineers in Weissach overhauled the motor to comply with incoming European regulations, and added more power before slotting it into the new, 502-hp 911 Speedster. Now, according to Autocar, the upgraded 4.0-liter will head right back to the 992-series GT3 that could debut later this year in Frankfurt.

Andreas Preuninger heads Porsche’s GT division, and has said in the past that he wants to power the GT cars with naturally aspirated engines for as long as possible. He told Autocar, “We’ve invested in the future with this engine. I can’t comment on future projects, but we would be stupid not to re-use this engine somewhere.” And during the 911 Speedster launch, 911 spokesman Holger Eckhardt said Porsche wouldn’t spend on all the engine upgrades for a single model that will sell just 1,948 units.

The flat-six’s advances include individual throttle bodies for much better response, higher-pressure injectors with a better spray pattern, and a stainless steel exhaust that’s 22 pounds lighter than before even with two Euro-mandated particulate filters.

It’s possible the same engine will make its way into special editions of the 718 Cayman and 718 Boxster twins as well. Road & Track reported that the coming Cayman GT4 will get the GT3’s 4.0-liter engine, the old 3.8-liter from the older GT4 reserved for the track-only GT4 Clubsport. Carscoops believes that engine in the junior sports cars will come in at around 425 horsepower. Carscoops also reports, however, that there will be Touring versions of the Cayman GT4 and Boxster Spyder that will also get the 4.0-liter, downrated to perhaps 380 hp.

If all this came to pass, that would mean seven other potential models powered by the 4.0-liter — GT3, GT3 RS, 718 Cayman GT4, 718 Boxster Spyder, two Touring versions of the 718 models, and a Cayman GT4 RS. We haven’t heard the Speedster going hard at it yet, but based on a GT3 prototype putting on a flat-six concert at the Nürburgring, we’d have no complaints.