At the car selection screen, hold R1 + R2 + L1 + L2 + Select + Down + Triangle. Then, all cars in the game will be selectable. Normally, the cars are unlocked as followed:

Extra cars

Finish in first place on all three tracks with the settings on normal enemy level and orthodox race style. Four additional cars (two different cards with automatic and manual transmission versions) will be available in the car selection screen: Red #1 (automatic), Blue #11 (manual), Yellow #2 (automatic), Green #12 (manual).

Racer X's car

Finish in first place on all three tracks with the settings on normal enemy level and endurance race style. Racer X's yellow #9 car will be available in the car selection screen. The light yellow car has an automatic transmission. The dark yellow car has a manual transmission.

Demon cars

Enable the "Extra cars" and "Racer X's car" codes. Finish the first trace in first place using Racer X's #9 car in Time trial mode. A red Demon car with a automatic transmission, and a black Demon car with a manual transmission will be available in the car selection screen. Note: These cars are called Ogre cars in the Japanese version of the game.

GXR car

Race on the medium or hard track and go through the tunnel. Look on the left for a small passage with a wall. To break through the wall, go over 190 mph, bump the statues on the left out of the way, then use the saws to crash through the wall. Drive straight ahead to find the white GSX car. It has A++ ratings for auto and manual.