Successfully complete Advanced tracks to unlock the #8 HSV with a spoiler, the Lightning HSV with a spoiler, and the Flower HSV.
Alien HSV
Successfully complete the Professional Championship.
Cheat option
Begin game play in one player championship mode on the Coventry Cove track. Locate the shortcut near the barn with two haystacks. Intentionally drive into the haystack closest to the track and hit the Daisy Box hidden inside. The word "Groovy" will confirm correct trick entry. Successfully complete the race. A "Cheats" selection will now appear on the options screen.
Novice level bonus cars
Successfully complete Novice tracks to unlock a racing striped HSV, the #8 HSV, and the Lightning HSV.
Police HSV
Successfully complete all the standard Championships to unlock a bonus mode. Complete bonus mode to unlock the Police HSV. Hold C-Left while driving that car to turn on the siren. This will cause the other racers to slow and stop.
Quick start
Quickly press L when "Go" appears at the start of the race. When done correctly, your car will begin the race at over 40 mph.