Quick Start:
Press to accelerate when "1" appears during the pre-race countdown.

All Cars & More:
Enter NORTHEND and it will open up a secret menu to access all cars and extras in options menu.

Unlock Everything:
Go to the option screen and hold down L1 and press , , , and then hold R2 and hit Start and if it worked the whole screen will shake. ALSO
reported as during game press start button and press L1,R1,L2,R2,L2,L1 then go back to main menu and you will all cars, all stages and all engines.

New Engine:
Go to time attack and beat all the countries, get a new engine for all cars!!!

Secret & Top Secret Menu:
In the options menu hold down and press: Up, , Down, , Left, Right, Left, Right, . This opens up a secret menu on the options screen,allowing you to open up all 9 stunt tracks.

 

Thanks to Revolution reader Wes Howe!