While you are at the mode selection screen, press Y, X, Right, Left, Right, Left, Down(2), Up(2). Alternately, successfully complete expert mode in first place with the Coyote.

T4 fighter jet

While you are at the mode selection screen, press Left, Right, Down, X(4). Alternately, achieve 100% on the level checker when building your car.

Additional colors

While you are at the mode selection screen, press Down, Left, Up, Right, X, Y, L, R to unlock a fourth color set. Alternately, successfully complete expert mode.

Random weather in time attack mode

While you are at the mode selection screen, press R, X(7), Y(7).

Super expert mode

While you are at the mode selection screen, press Left(2), Right(2), Left, Right, X, Y(8). Alternately, successfully complete expert mode on the championship difficulty with the Beelzebub Buggy.

Beelzebub Buggy

Beat expert mode in first place.