This will be one of the last two achievements you get. Here is a complete roadmap on what you have to do before you can get this achievement.
To unlock the LEGO Speed Champion
Event Brick Challenge you need to complete every other Brick Challenge:
This will give you enough bricks to fully upgrade your house:
The remaining 2,500 bricks are required to unlock the LEGO Speed Champion challenge. Then you can enter the LEGO Speed Champions Finale. It's two laps around LEGO Valley in any LEGO Speed Champion car, and will take about 6 minutes. On winning you will unlock the achievement, and get the last 1,000 bricks required to build the Speed Champions Trophy.
Since the LEGO Speed Champion challenge is the last Event Brick Challenge you will also unlock this achievement at the same time: