The REALLY Weird Aerodynamics Of The Corolla GR

Summary

The video analyzes the Toyota Corolla GR Hatch’s aerodynamics using CFD simulations. It compares the car with and without its rear wing, examining airflow, pressure, downforce, and drag around key features. Its central point is that several unusual design choices work reasonably well together, but often involve compromises.

Rear Wing and Downforce

• In the simulations, adding the rear wing increases estimated downforce from about 55 kg to 80 kg at 120 km/h—roughly a 40% improvement.
• The wing does not behave like a conventional wing across its full width. In the center, it connects to the roof-mounted structure and acts more like a raised spoiler.
• Air separates beneath the wing rather than smoothly following its underside. The narrator attributes this to the airflow having to pass over the roof, encounter the wing, turn underneath it, and then turn again—a process made more difficult by the wing’s blunt leading edge.
• In the central area, the main downforce effect comes from increased pressure in front of the spoiler pressing down on the car, rather than from a large pressure difference above and below the wing.
• Away from the center, gaps reduce that pressure effect. The wing contributes little downforce in those regions while still adding drag.
• The simulated drag coefficient rises from approximately 0.34 without the wing to 0.36 with it. The narrator considers this a substantial drag cost for the downforce gained.

Underbody and Balance

• The front lip produces low pressure under the front of the car, while the rear underbody has higher pressure. The narrator interprets this as evidence of a working front lip but little or no conventional rear diffuser.
• The car’s sloped floor nevertheless acts somewhat like a large, extended diffuser, providing underbody flow expansion without a dedicated diffuser structure.
• The resulting downforce balance is relatively front-focused. The narrator says this may help cornering and stability, though it could make the rear feel lighter at high speed.
• The front lip also causes flow separation across much of the car’s width, adding drag.

Front End, Hood, and Cooling

• Large front openings allow substantial air into the engine compartment, supporting cooling but increasing aerodynamic resistance.
• The narrator credits the downward-sloping hood with helping align airflow from the hood to the windshield, reducing how much the flow must turn.
• Hood vents release air from beneath the hood. This can lower under-hood pressure and reduce lift, while the redirected airflow may also help feed the rear wing in the wing-equipped simulation.
• The vents create significant drag and turbulence because air exiting them does not always align cleanly with the surrounding flow.

Wheel Airflow and Rear Separation

• The front air curtains capture air near the front of the car and guide it around the front wheels. The simulations show a smaller wheel wake, although the devices themselves also add some drag.
• The narrator suggests that guide vanes could redirect the incoming air more gradually and potentially improve the arrangement.
• A vent behind the front wheel appears to release some air from the wheel well. This may reduce wheel-well pressure and limit air spilling out beside the wheel, but substantial drag remains.
• The rear wheel arches also disturb the flow: air pushed out of them can cause airflow over the body to separate earlier than intended. The narrator suggests that additional or better-connected vents behind the arches might help.
• Sharp rear edges help the airflow separate cleanly. The rear window is one example: the flow breaks away at the back, which may reduce wake fluctuations and average drag.

Overall Conclusion

The Corolla GR’s aerodynamics are presented as a collection of unusual compromises. The rear wing adds downforce but also noticeable drag; the underbody favors front downforce rather than relying on a conventional rear diffuser; and the cooling openings support performance while increasing resistance.

The narrator concludes that the car performs reasonably well despite its relatively high drag, much of which is attributed to cooling requirements and design choices made to support power and handling.

Speakers and Sources Featured

• An unnamed narrator and presenter from the Premier Aerodynamics channel explains the vehicle analysis.
• The presenter conducted the CFD simulations using OpenFOAM, including comparisons with and without the rear wing.
• The narrator mentions that a friend requested the review; the friend is not heard speaking in the subtitles.