NASCAR Heat Evolution

This seems to have multiple unlock conditions, but a one definite way to unlock this is to get 20,000 Speed Points (SP). If you're wanting to grind these out quickly, choose a short race with a lot of laps, such as Bristol or Dover. The amount of SP you gain from each race is your Speed Rating for that race multiplied by the number of laps, so many short laps will get you more points on a time per points basis.