It's one of the best-sounding cars we've heard at Johnny Bohmer Proving Grounds.

Here’s something we’ve never seen tackling the miles-long runway used by Johnny Bohmer Proving Grounds. It’s not the Porsche 911 – we watched a bone stock GT2 RS hit 219 mph last May. This 911, however, is a full-on GT3 Cup race car and we won’t even try to tease you about speed. With a flat-out pass of 172 mph, it’s not remotely as fast as other cars recorded at the Space Shuttle runway. But it’s probably the only one that could take a corner flat-out and not end up spinning like a malfunctioning UFO. And it sounds absolutely glorious.

Specifically, this is a 2017 911 GT3 racer with downforce galore. Its naturally aspirated 4.0-liter flat-six develops 485 horsepower (362 kilowatts), with shifting duties handled by a six-speed sequential gearbox. Being a race car it’s also stripped down and weighs just 2,646 pounds, which is absolutely noticeable as the car pulls 1.1 g under acceleration early in the run without even trying that hard.

Gallery: Porsche 911 GT3 Cup Top Speed Run

The sprint to 150 mph is where the Porsche’s racing modifications shine through. 485 hp actually sounds a bit low in an age of 700-hp muscle cars, but the GT3 accelerates like a car with twice the power. The downside to that is running out of gear at the other end of the speedometer, and indeed it appears the Porsche could’ve gone a touch faster if it only had a seventh gear. But here’s where it gets interesting – it did have seven gears. Or did it?

911 GT3 Cup cars run six-speed sequential transmissions, and this actual car was listed as having just that. We forced ourselves to watch and listen to this clip several times, and there are seven audible gear changes. Johnny Bohmer Proving Grounds isn’t just a home for speed freaks – a fair amount of prototype testing takes places so perhaps this car was exercising a racing version of the seven-speed dual-clutch transmission available in street-legal models. 

Go ahead, listen for yourself. We know it’s tough, hearing that opened up flat-six singing its horsepower tune. Do you hear seven gear changes, or is that first "shift" just back-pedaling from tire slippage?