The folks over at Porsche->ke1 are definitely up to something these days at the Nurburgring->ke999 track, as two more prototypes have joined the 911 Convertible and the Cayenne GTS for extensive testing on the track. This time around, the Germans were spotted hooning a couple of mid-engined Boxster->ke570 and Cayman->ke5 sports cars. Although both look like plain, flat-six-powered vehicles from the company's current lineup, there's more to these black-painted Porsches. And it all comes down to the engine note bursting from those center-mounted exhaust pipes.

Both cars sound different than any Boxster and Cayman we've heard up until now, and this can only mean one thing: Porsche is these shells and chassis to test its upcoming four-cylinder engines. Stuttgart has already confirmed there's a flat-four underway, but the Germans have declined to reveal further details. We expect the new powerplants to arrive in the facelifted versions of the current Boxster and Cayman. Three different units are rumored to emerge, with 1.6-, 2.0-, and 2.5-liter displacements. Each of them will be accompanied by turbochargers, with ouput to range between 210 and 360 horsepower.

There's no indication as to how big the engines hidden in these test cars are, but they do sound quite impressive under full throttle. Combine that with a hefty reduction in CO2 emission, improved fuel efficiency and a lower curb weight, and the result is downright impressive. All of a sudden downsizing sounds like a terrific idea! Hit the play button and tell us what you think.

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