A few months ago, we showed you video of a Porsche 718 Cayman testing on the Nürburgring sporting an unusual exhaust/diffuser setup, with an exhaust note very different from that of the normal 718's turbo flat-four. Many—including , who uploaded the video—speculated that this was the soon-to-be-revealed 718 Cayman T. But around a week later, the 718 T arrived with a flat-four and the same rear exhaust/diffuser design as the base 718.
We think what we're seeing here is sort of 718 Cayman GT4. Check out those exhaust tips and diffuser again—they appear identical to those on the 718 Cayman GT4 Clubsport race car, shown below. They certainly look the same as those on other too.
This prototype definitely sounds like it's got a flat-six, too, and we know that the upcoming GT4 will ditch the regular 718's turbo flat-four for a naturally aspirated six. It'll likely be a version of the 4.0-liter used in the 911 GT3, which is Porsche's only naturally aspirated motor certified for road-car use right now.
But, this car appears to have the same retractable wing as the regular 718 Cayman—not a big fixed wing like the previous GT4, or the new race car. To us, that seems to mimic the 911 GT3 Touring Package, which eschews the regular GT3's fixed wing for a retractable spoiler. This could mean Porsche is working on a 718 Cayman GT4 Touring Package—or perhaps this Cayman is just a test mule that doesn't reflect a car headed to production.
We've been going down the 718 rabbit hole as a result of that claims Porsche will use a flat-six in some additional models beyond the upcoming 718 Cayman GT4 and Boxster Spyder. There's good reason for Porsche to do this—718 sales have been down lately, possibly due to their turbo flat-fours, which haven't been warmly received. The company is looking to boost sales with the new GT4, which will likely offer an optional dual-clutch automatic transmission for the first time, to broaden its appeal.
The 911 GT3 Touring has been a success for Porsche. Perhaps a Touring variant of the 718 GT4 could be a similar hit.
Both Automobile and speculate that the Cayman and Boxster will see the revival of the old 3.8-liter flat-six, best known from the 2012-2015 911 Carrera S and the previous Cayman GT4. While that engine currently appears in the 718 Cayman GT4 Clubsport racer, we doubt it will be used in a new road car. It was put back into (limited) production for the new GT4 race car mainly because it was competition-proven, and familiar to the teams that ran the old Cayman GT4. But a knowledgeable source tells us that using this engine in a new road car would require significant re-engineering to meet current emissions regulations.
And finally, the twin-turbo 3.0-liter flat-six in the current 911 won't fit in the 718's tiny engine bay. In our estimation, the 4.0-liter is likely the only street-legal flat-six that can work in the current-generation 718.
What we know for certain is that Porsche has some plans for the 718 Cayman and Boxster. Last time I spoke with him, August Achleitner, Porsche's soon-to-retire sports car chief engineer, said there are multiple exciting 718 variants coming later this year. We'll just have to wait to find out how many of them have six cylinders.