As described by rapper 2 Chainz aka Tity Boi in his documentary "Codeine Cowboy", the Chromed Out 1100 is a sexual act in which a man lays a woman face-down on a bed (or other suitable surface) with her arms and legs extending to each side of the bed. The man then mounts, penetrates, and proceeds to "ride" the woman as he grabs onto her hands as if he were riding a motorcycle. The "vroom" noise can then be made for added effect.
It is named after the famous Yamaha motorcycle, as mentioned in the Birdman & Lil' Wayne track "Stuntin' Like My Daddy"
Homie 1: "What happened after she came over to your crib?"
Homie 2: "We got wasted and later on I did the Chromed Out 1100 on her. The greatest sex I've ever had."