Porsche Built A 750-HP Cayman With A 5.0-Liter Twin-Turbo Flat-Eight

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This monster mill was supposed to be fitted to a Carrera GT/918 Spyder replacement.

The majority of Porsche's high-end sports cars have relied on six-cylinder engines, but it turns out that the famous brand got close to releasing a sports car with a 5.0-liter twin-turbocharged flat-eight engine. Bizarrely, this engine was linked to the same project that led to the release of the four-cylinder 718 Cayman.

The secrets surrounding this mystery flat-eight engine came to light when The Intercooler sat down to have a chat with Marcos Marques, Porsche's global e-fuel expert. Porsche's continued interest in e-fuels is promising at a time when traditional gas engines are approaching bans, but that's a story for another day. This one is about the flat-eight engine that made 750 horsepower.

Marques was responding to a question about how the four-cylinder Cayman came to be when he spilled the beans on the secret engine. He said that the Cayman was "originally part of a bigger project, one that involved another car that would have made a lot more sense of the flat-four project."

2022-2023 Porsche Cayman GT4 RS Lateral View Porsche

Pressed for more information, Marques continued. "Well, to be fair, you only ever saw the first half of this story because we had another engine, running in another car, using the same design but bigger, and it was a lot more interesting," said Marques. "It had eight cylinders, not four. It also had two turbos and was running in a Cayman chassis for a while with 750 bhp, 1,000 Nm [738 lb-ft of torque], and a 9,000-rpm red line. It was a crazy car and it sounded amazing, as you can imagine, but that engine in a Cayman chassis with a manual gearbox was also quite wild."

Considering that the current top dog in the Cayman range delivers 493 hp - that honor going to the $160,700 Cayman GT4 RS - and will streak to 60 mph in 3.2 seconds, it's difficult to imagine what a 750-hp eight-cylinder mill would do in the same vehicle.

2019-2023 Porsche 718 Cayman Badge Porsche

However, this 5.0-liter twin-turbo eight-cylinder was supposed to power a larger mid-engined car that would replace both the Carrera GT and 918 Spyder. A prototype of this car was tested on the roads close to Weissach for a period of over a year, but it remained nameless. And then, out of the blue, the decision-makers at the head of the company decided that the timing for this eight-cylinder sports car wasn't right, and it was canceled.

As recently as 2016, rumors were still circulating of a Porsche 960 with a flat-eight quad-turbo engine that would compete with the Ferrari 488, but it never saw the light of day either.


Marques also admitted that a quad-turbo version of the 991-gen 911 was another project he was involved in. However, four small turbos were determined to be too challenging to package in the rear of the 991 relative to two larger turbos. "We had the sequential four turbo technology already developed from many years earlier - from before the Veyron - and Bugatti ended up using this technology on the Veyron itself."

A second-gen Audi R8 with a five-cylinder mill and a V10-powered Volkswagen Golf 5 are another two engine projects that Marques was privy to that ultimately never made it to production.

As Porsche's electrification strategy gains traction, the narrow window where an eight-cylinder Cayman or other Porsche sports car may once have been deemed a possibility has probably passed. Of course, there's always someone out there who's willing to cram a big V8 into a small car like the Cayman.


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