It may look just about the same as the old one, but it's hiding a big secret in the engine bay: the 911 GT3's 4-litre unit.

It's the car that came in from the cold – we've seen this new example of the Porsche Cayman GT4 testing in the snow recently, but now the fun has move to the Nürburgring, where our photographers have spotted the prototype in action. The crown jewel of the Cayman range is currently undergoing final testing at the Nordschleife without wearing any sort of disguise. As you would come to expect from Porsche, the styling revisions will be kept to a minimum, but don’t let that trick you into believe the new version of the car will mean more of the same.

That’s because the Cayman's predecessor’s 3.8-litre engine will be retired to make way for a bigger 4-litre flat-six, naturally aspirated motor. If this move sounds a little bit familiar, it’s because the Boxster Spyder will also use this engine by borrowing it from the same 911 GT3.

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Of course, in order to avoid stepping on the toes of the superior model, Porsche’s engineers have apparently detuned the flat-six to produce around 400bhp. That number sounds just about right as it would allow the Cayman GT4 to provide a nice power advantage over the 350bhp Boxster/Cayman GTS without invading the 500bhp 911 GT3’s territory.

While you’ll be able to drive the facelifted Cayman GT4 outside of a track, it’s going to be a different story with the Clubsport version. Caught on camera at the Monza circuit late April, the race car is also getting a refresh and this time around it will be available to a broader audience as the plan is to increase production beyond the previous version’s 400+ examples.

The Clubsport is scheduled to debut early 2019, but the good news is we won’t have to wait much longer to see its roadgoing counterpart. The new Cayman GT4 is set to debut towards the end of the year and hopefully the Boxster Spyder will follow shortly after.

Gallery: Porsche 718 Cayman GT4 facelift new spy photos