The "Django Unchained" actress who claimed she was harassed and hurt by cops after making out with her boyfriend was actually having sex in her car according to witnesses ... then went on a rant with cops accusing them of racism and not knowing who she was ... according to police audio obtained by TMZ.

Daniele Watts had just left CBS studios in the San Fernando Valley around 2 PM Thursday. She says she was making out with her BF, but we've learned witnesses from the nearby Art Directors Guild office building told cops they were watching her and her BF have full-on sex in the passenger seat WITH THE DOOR OPEN!

The eyewitnesses said the guy was sitting in the seat, she was straddling him and it was for everyone to see. One eyewitness told cops they cleaned themselves up afterward with a tissue.

TMZ obtained police audio of the incident. Watts instantly plays the race card when Sgt. Jim Parker asked for her ID. She quickly moves from the race card to the fame card -- then storms off, refusing to show her ID.

While Watts was gone, Sgt. Parker had a very cordial conversation with her BF Brian.

She was apprehended by another cop a short distance away and brought back -- and things got NUCLEAR!

Some of her choice comments:

- "I think I'd like to identify you ... to my publicist."

- "I hope when you're f***ing your spouses you really feel alive."

We're told she plans to file a complaint with the LAPD and has hired a lawyer.