On 18 April, the new Bentley Continental GT Speed achieved its top speed through the 14.5 km Ryfylke tunnel in Norway the longest road tunnel, and deepest subsea 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 secondgeneration renewable biofuel and a hybrid battery charged with electricity from Bentley’s own solar panel array.

13 months of preparation and planning was needed to achieve the highspeed tunnel run safely. Every new Continental GT Speed can reach its top speed without modification beyond inflation of the tyres to the correct highspeed 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 metrewide 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 highspeed runs with a roll cage and bucket seats – was fitted with 22” Pirelli tyres that had been xrayed 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.

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