Rolls-Royce Cullinan Teams Up with Hennessey for an 850-HP SUV

John Hennessey is obsessed with adding power to anything that moves. Along with his team at Hennessey Performance in Texas, he aims to crank up the output of every vehicle. Their latest project is the spectacular Rolls-Royce Cullinan. According to Hennessey, a current Cullinan owner has already commissioned them to boost his SUV to 850 horsepower. Out of the factory, the Cullinan puts out 563 hp from its 6.7-liter twin-turbo V12. Many might be surprised to learn that Rolls-Royce actually uses a BMW-built engine, but Hennessey sees it as an advantage—his design and engineering experts are already familiar with how to extract more power.

Hennessey admits it’s more difficult and expensive to add power to a naturally aspirated engine, but he’s confident they can hit the target with the Cullinan. In fact, he’s planning to offer the upgraded Cullinan as an official future performance package, anticipating strong interest from other buyers.

So who’s the first person to own an 850-hp Rolls-Royce Cullinan? You might picture a celebrity or high-powered executive, but it’s actually a potato farmer from Wisconsin. A very successful, wealthy grower who even flies his private jet down to Hennessey Performance in Texas. As soon as he took delivery of his Cullinan, he asked Hennessey to give it the extra punch he wanted.

This custom Cullinan will far outgun the Rolls-Royce Wraith coupe, currently the brand’s most powerful model—thanks to Hennessey Performance’s knack for turning luxury cars into beasts. They’ve performed similar upgrades on the McLaren 600LT, the Jeep Grand Cherokee Trackhawk, and the Cadillac CTS-V, each tuned to over 1,000 horsepower. While the Cullinan won’t reach that level, its 850-hp goal represents more than a 300-hp increase over stock.

It’s not the Wisconsin farmer’s first ride tuned by Hennessey. He previously commissioned a Goliath 6×6 pickup—based on the Chevrolet Silverado Trail Boss—with a triple axle and 700 hp. He loved it so much that he couldn’t wait to return when he bought his Cullinan. “We turn down many projects,” John Hennessey says, “but tuning the Cullinan was one we couldn’t refuse. Transforming a classically beautiful Rolls-Royce into a powerhouse—now that’s a challenge.”

Modifying the Cullinan flies in the face of typical Rolls-Royce expectations. While these cars are certainly powerful, they’re better known for elegance, smoothness, luxury, and comfort. Once Hennessey extracts 850 hp, the custom Cullinan will upend those preconceptions.

The Cullinan is Rolls-Royce’s first SUV, marking its entry into the luxury SUV market. Named after the Cullinan diamond—the largest gem-quality rough diamond ever found—it was officially unveiled at the Concorso d’Eleganza Villa d’Este in May 2018, with production starting later that year. The concept was developed in 2016, and testing began in 2017. U.S. prices start at $345,000, with optional upgrades available at extra cost. Early deliveries began in early 2019, and critical reception has been favorable so far.