To get a faster engine select multi-player mode. Press X + Square + Triangle + Circle at the track selection screen. An engine will be displayed at the bottom of the screen to confirm correct code entry.
To unlock jumping cars select multi-player mode and select a track and car. Press Circle + Left when the countdown that marks the start of the race begins.
To unlock night racing hold L1 + L2 + R1 + R2 while selecting a track until headlights appear in front of the car. A new symbol will appear on the track to confirm correct code entry.
To reverse the tracks choose a track and press Select. Quickly hold X + Square as the cars enter the tunnel. While continuing to hold those buttons, press Left or Right. The cars will turn around and enter the tunnel in reverse to confirm correct code entry. Alternatively, press L2 + R2 + X + Down at the track selection screen. An arrow will appear to confirm correct code entry.
Pause game play in single player mode. Enter the "Sound" option, highlight the "FX Volume" selection, and press L1 + L2. Then press Triangle to exit the screen.
To unlock upside down tracks press L1 + R1 + X + Down at the track selection screen. An arrow will appear at the bottom of the screen to confirm correct code entry.