How do you unlock the expert staff ghost data on Mario kart wii?

On time trials you have to beat a person of the Mario Kart Wii staff ( staff always have NIN next to their name ) by 7 seconds or more.

On time trials you are goin' to have to beat a regular staff ghost by at least seven seconds.Here is characters and karts unlocks by getting expert staff ghosts!

Funky Kong- unlock 4 expert staff ghosts

Baby Luigi-unlock 8 expert staff ghosts

Rally Romper-unlock 1 expert staff ghost

B Dasher Mk.2-unlock 24 expert staff ghosts