BY DIRECTING AIRFLOW BENEATH THE WORKING UNDERFLOOR, AIRSTREAM IS HARNESSED TO GENERATE POWERFUL, STABILISING DOWNFORCE
The McLaren F1 is the world’s first production car to feature full ground-effect aerodynamics with fan assistance.
Subscribe to evo magazine
By careful management of airflow between the McLaren F1’s underfloor and the moving road surface beneath, powerful aerodynamic forces can be harnessed – as in Formula 1 – for the driver’s benefit.
Management of this airflow regime has come to be known as a ‘ground-effect’ aerodynamic system.
Airflow beneath the car is compressed against the underlying roadway and then released through an expanding-section exit channel at the car’s tail – the curving underfloor surface of which is known as the ‘diffuser’. As airflow velocity has been accelerated through this underfloor ‘venturi’ system, so the pressure within it falls, and this low pressure area may then be harnessed as ‘downforce’ to suck the moving car bodily down against the roadway.
In 1978 Gordon Murray stunned the Formula 1 racing world by creating the Swedish Grand Prix-winning Brabham BT46B ‘Fan Car’ driven by Niki Lauda, which generated massive aerodynamic downforce in part by fan assistance. Formula 1 rules were quickly altered to dismiss such devices!
Now, with the McLaren F1 project governed only by comparatively liberal international road-car regulations, that ‘Fan Car’ theme is to some extent being re-introduced.
A complex three-part rear diffuser beneath the F1’s tail incorporates a central single surface and two reflex shapes each side generate sufficient downforce to overcome the car’s natural aerodynamic lift.
Simultaneously, two powerful electric fans remove boundary layer air from the rolled S-wave of ‘reflex’ diffuser sections, helping to control movement of the Centre of Pressure – the truly significant aerodynamic factor affecting vehicle stability and handling.
