Sauber F1 team bring in a passive double-DRS system at Belgium GP, like Lotus F1 team current model. Showing like its two ‘ears’ alongside the airbox hole.
F1 official F1 website explained that, “further back a single pipe then blows the air under the bottom of the main plane of the rear wing. The idea is that this reduces drag and increases top speed on the straights.”
“The difficulty is in getting the airflow to separate and then reattach successfully to the rear wing. Sauber trialled the system on Gutierrez’s car on Friday, but opted against running it in qualifying and the race.”