It doesn't sound like either the supercharged V6 or V8.
We learned last January that Jaguar is planning to make its F-Type roadster and coupe available with a turbocharged four-cylinder in the near future. Not only will it be more fuel efficient than the current supercharged V6 and V8 engines, it'll also be lighter. It will sit further back in the engine bay, thus improving overall agility with even less weight on the front wheels. And now an F-Type test mule powered by that new turbo four has been spotted testing on the Nurburgring.
How can we tell it's not a V6 or V8? Just listen. It's not nearly as loud as the current engines offerings. More than likely, the turbo four will serve as the entry-level model F-Type, and we wouldn't be surprised to see it have a sticker price below the current $69,000 base convertible. In all likelihood, this engine will debut sometime in 2015.