[freebeard]

More downforce with less drag.

https://grassrootsmotorsports.com › articles › downforce-sorcery-diffusers-explained
Downforce Sorcery: Diffusers Explained | Articles - Grassroots Motorsports
21 May 2021Since the diffuser is making downforce, there is likely to be an increase in drag. Generally this effect is small at normal speeds, but it can be substantial as a car approaches terminal speed. The key, of course, is designing an effective diffuser and then properly testing and tuning it for maximum efficiency. Like what you're reading?

https://www.carid.com › rear-diffusers.html
Custom Rear Diffusers | Carbon Fiber, Fiberglass, Urethane - CARiD.com
1 Oct 2021Although components like rear wings can also be used to provide downforce, they create much more aerodynamic drag while doing so than a rear diffuser. The diffuser provides the space for the high velocity, low pressure air flow to decelerate and expand at the rear of the vehicle, creating a pressure differential and more downforce.