Rear Mounted Fan on Gordon Murray Automotive T.50 Explained

The T.50 takes road-car aerodynamics to entirely new levels, with Murray rewriting the rule book to significantly enhance the supercar’s ground-effect capabilities. To achieve unmatched aerodynamic performance, the car’s rear-mounted 400mm fan rapidly accelerates air passing under the car, forcing it through active boundary-layer control ducts that form part of the rear diffuser.

Through the application of two automatic and four driver-selected aero modes, the T.50 is capable of increasing downforce by 50%; reducing drag by 12.5%; adding around 50PS to the car’s output in combination with ram-air induction; and cutting braking distance by 10m from 150mph.

The fan and its associated ducting system improve on conventional ground-effect systems by actively managing both underbody and overbody airflow. This boundary layer control ensures the most effective interaction of airflow on top of, and below the car, balancing drag and downforce at all speeds.

This same fan-assisted aerodynamic enhancement was first used for the road on Murray’s F1 supercar. Few realise that two fans had been employed to pull air from under the car as these, far smaller, fans were hidden beneath each of the F1’s rear haunches.

The underbody airflow system not only enhances performance, but also allows purity of design for the car’s upper surfaces. Air flows over the top of the car undisturbed by unsightly vents, ducts, or flaps. The fan interacts with a pair of active spoilers at the rear, which can contribute to downforce or reducing drag, as required.

The fan is driven by a lightweight 48-volt motor, spinning at up to 7,000rpm. The unit’s design and underbody ducting does away with the need for a ‘skirt’ – like that used by Murray’s Formula One BT46B Fan Car. Vertical inlet ducts fitted with filters ensure no road debris can pass through the fan.

The T.50 features six different aero modes that optimise performance for different scenarios to balance traction and outright performance. The fan aero system has six modes – two are automatic (Auto and Braking), the remaining four (High Downforce, Streamline, V-Max Boost and Test Mode) are driver selectable:

‘Auto Mode’ is the car’s default setting. In this mode, the T.50 operates like an ordinary supercar with passive ground-effect downforce.

‘Braking Mode’ automatically deploys the rear spoilers to their maximum (+45 degree) angle when high levels of deceleration are required. The fan also operates simultaneously at high speed while the diffuser valves open. This function can double downforce, enhancing stability and grip, and shortening the 150mph-to-0mph braking distance by a full 10 metres. If sudden deceleration is required, and when aerodynamics could influence stopping distance, Braking Mode overrides all other modes.

‘High Downforce Mode’ is driver selectable and delivers enhanced traction – in this mode, the rear spoilers deploy at +10 degrees, diffuser valves open, and the fan spools up to increase downforce by 50%.

‘Streamline Mode’ cuts drag by 12.5% and boosts straight-line speed while also reducing fuel consumption and downforce. In this mode, the rear spoilers deploy to -10 degrees reducing base suction and drag. The diffuser valves close partially, stalling the diffuser and reducing downforce, which saves wheel travel to make the car more comfortable and efficient. It also sets the fan to operate at high speed, drawing air from the top deck to minimise drag while extending the trailing wake of the car, creating a ‘virtual longtail’ and producing 15kg of thrust.

‘V-Max Boost’ is the most extreme T.50 mode. It uses the characteristics of Streamline Mode, then uses the car’s 48-volt integrated starter-generator to drive the fan – freeing up power to the driveshaft. Combined with the ram-air induction, this boosts power to 700PS for short bursts of acceleration.

‘Test Mode’ operates when the car is stationary and is driver-selected. The fan spools up to its maximum 7,000rpm, the twin rear spoilers cycle through their full range of movement and the diffuser ducts / valves progressively open and close before returning to their rest position.

Monitoring the level of static and underbody pressure provided by the combined fan and diffuser system is possible via an interior gauge – displayed on the left-hand dashboard screen.

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