Easiest way is to boost with a friend or someone on TA. Pick Ranked match, then set track as "Peak", NOT PEAK REVERSE. Set the game to 100 points to win and knock out mode. When the game starts, go just past the start/finish line, and you and your friend turn around. You have to drive the wrong directon on the track. Once one of you passes the start/finish line going the wrong direction, a timer will pop up in the top middle of the screen. Complete the lap in 18.1 seconds or under and the achievement should pop for you. Good Luck!!