A load of hot air
Aglance inside the engine bays of either M-Sport or Toyota’s 2017-’21 WRC machines reveals a plethora of complex, sculpted ductwork. While these undoubtedly contribute to cooling the powertrain, control of the inlet and exhaust flows from the engine bays were also put to good use in influencing the cars’ aerodynamic performance.
Taking the M-Sport Fiesta as an example, air is fed through the intercooler from the front grille, pulled by a pair of large fans sited behind the air-to-air heat exchanger, before being vented out over the bonnet. One engineer explained that this high temperature air rejoins the flow over the front of the car at the trailing edge of the front wheelarches, the idea being to create a separation boundary layer in this area, forcing the air that is disturbed by the rotating wheel away from the car. This has the effect of reducing the turbulent airflow directly influencing the front of the car, improving the performance of the aerodynamic devices.
The vent sizing could be adjusted on different events to balance the potential aero gains against the cooling needs of the engine, helped by the fact that many of the components fell under the ‘variant’ heading of the rules, meaning jokers were not needed to alter them.
This is a fiendishly complex area of aerodynamic development, requiring advanced CFD simulation to figure out. As such, from 2022 onwards, it has been deemed an unnecessary excess, with much tighter control over duct design and development brought in. Still, it was interesting while it lasted.