The Bentley Continental GT Underwater Speed Record – Behind The Scenes

The new, fourth-generation Continental GT Speed will make its global public debut at this week’s Goodwood Festival of Speed. Fresh from claiming an unofficial ‘Underwater Speed Record’ – believed to be the fastest a car has ever travelled through a tunnel – the 208 mph / 335 km/h daily supercar will appear at the event in both coupe and convertible versions and run on the famous Goodwood Hill Climb twice a day from Thursday until Sunday.

Along with the two examples of the new Continental GT Speed that will appear on the Hill Climb at Goodwood, a third car will be on display at the Festival of Speed in a unique way to celebrate the underwater speed record. The ‘FOShtank’ is a bespoke version of the glass ‘Toy Box’ display units that Bentley utilises across its Dream Factory campus in Crewe, England, but modified to include a custom-built fish tank in a tongue-in-cheek take on the underwater theme.

The Tourmaline Green Continental GT Speed display car will appear behind a three-tonne fish tank containing 1,400 litres of water and 30 Shubunkins and other goldfish. Two separate tanks together weigh more than three tonnes when full, with the water held back by 80 mm thick acrylic sheets. Each tank is flow-rated and filtered to ensure the water is clean, and an on-site aquarium specialist will be looking after the welfare of the 30 occupants over the course of the Festival of Speed. The back wall of the display will house a large, outdoor LED screen that will play both the Underwater Speed Record launch film and a new behind-the-scenes look into how the record was achieved.

The Underwater Speed Record – Behind The Scenes

On 18 April, the new Continental GT Speed achieved its top speed through the 14.5 km Ryfylke tunnel in Norway – the longest road tunnel, and deepest sub-sea tunnel of any kind in the world, with its lowest point 292 metres below sea level. Powered by Bentley’s new Ultra Performance Hybrid electrocharged powertrain, the new Continental GT Speed was able to deploy all 782 PS and 1000 Nm with ease, running on Coryton’s SUSTAIN second-generation renewable biofuel and a hybrid battery charged with electricity from Bentley’s own solar panel array.

The new class-leading powertrain delivers extreme performance with more horsepower and more torque than the outgoing W12, together with a significant drop in CO2 to 29 g/km. In turn, this provides an extraordinary range of driving capability, from extreme performance to silent and effortless electric luxury.

13 months of preparation and planning were needed to achieve the high-speed tunnel run safely. Every new Continental GT Speed can reach its top speed without modification beyond inflation of the tyres to the correct high-speed pressure, but for the run in the confines of the tunnel, extra precautions were needed.

The first step was to secure the right tunnel. The Ryfylke Tunnel near the town of Stavanger in Norway was the perfect candidate, being relatively straight, smooth and with large reserves of length. Bentley is grateful to the support of the Norwegian highways authority (Statens Vegvesen) and the local Stavanger police for their unwavering support of the project, in securing both the tunnel and the permit required to exceed the speed limit.

The physics of the car at ‘Vmax’ (top speed) in a 10 metre-wide tube were simulated using Computational Fluid Dynamics, revealing that aerodynamic drag would be 11 per cent higher in the tunnel. The aerodynamic loadings on the car were also affected by the shock waves and wake of the car bouncing off the tunnel walls, meaning that Bentley’s body engineers also had to assess the atypical forces on the panels around the car. Simulation showed the importance of running the car in the centre of the tunnel – proximity to the sides would accelerate the flow of air between the car and tunnel wall, creating a suction that would pull the closer ever closer to the wall.

The Vmax car – prepared exclusively for the high-speed runs with a roll cage and bucket seats – was fitted with 22” Pirelli tyres that had been x-rayed to check for any inconsistencies beneath the surface. The car was driven for the run by former British Rally champion Mark Higgins, who holds the lap record around the Isle of Man TT course. The top speed runs were carried out at a local time of 01:00 in the morning, when closing one of the two tunnels would cause minimum disruption to local traffic, which was routed to the spare tunnel to avoid delays. Despite the increased drag, the new Continental GT Speed accelerated from standstill to 335 km/h in just 33 seconds, and was able to hold top speed for as long as the film’s director, Jon Richards (formerly of Top Gear) required.